Juan Carlos Palacios Albarrán

Universidad de Extremadura | UNEX · Department of Organic and Inorganic Chemistry

This paper explores and revisits in detail the formation and characterization of sugar-based aminonitriles, whose ultimate origin can be traced to the interaction of biomolecules with cyanide. Although the synthesis and spectroscopic data of 2-amino-aldononitriles were reported long ago, there are both contradictory and confusing results among the...

This paper thoroughly explores the formation of Schiff bases derived from salicylaldehydes and a conformationally restricted amino alcohol (1-amino-2-indanol), as well as the generation of 1,3-oxazolidines, a key heterocyclic core present in numerous bioactive compounds. We provide enough evidences, both experimental-including crystallographic anal...

Polyhydroxylated phenols are components of biomass and precursors of pigments in plants. This paper reports a novel entry to xanthene dyes, involving the reaction of 2,4,6-trihydroxybenzaldehyde with primary aliphatic amines....

This work is aimed at providing a systematic and comprehensive analysis of the anomeric effect exerted by the isothiocyanato (N[double bond, length as m-dash]C[double bond, length as m-dash]S) group taking the xylopyranose ring as a scaffold because enhanced effects have been detected in that ring-bearing halogen and pseudohalogen substituents. To...

The facile reaction of a readily available aminopolyol from the chiral pool, N-methyl-d-glucamine, which avoids the side reactions usually associated to anomers of amino sugars, with epoxide and polyepoxide derivatives, enables the preparation of new non-ionic surfactant-like structures combining hydrophilic and hydrophobic moieties. The molecular...

Construction of enantiopure carbohydrate conjugates incorporating heterocyclic fragments is often hampered by the necessity of protection/deprotection protocols and multistep routes. Here we show the preparation and structural features of a broad series of chiral 1,3-oxazolines and 1,3-oxazines embedded in a hydrophilic chain based on glycamines, w...

This manuscript describes a thorough study on the thermal and photochemical evolution of carbohydrate‐based azoalkenes, which have been proposed as putative intermediates en route to other heterocyclic derivatives and nucleoside analogues. These substances represent new protagonists in the azo chemical space, under intense study due to reversible p...

Imine and enamine bonds decorate the skeleton of numerous reagents, catalysts, and organic materials. However, it is difficult to isolate at will a single tautomer, as dynamic equilibria occur easily, even in the solid state, and are sensitive to electronic and steric effect, including π-conjugation and H-bonding. Here, using as model Schiff bases...

A one-pot procedure for preparing a series of chiral imines by direct condensation of D-glucamine with 2-hydroxyacetophenones is described. Under conventional acetylation an unexpected mixture of two different peracetylated molecules is obtained, one with an open enamine structure, and the other incorporating an N-acetyl-1,3-oxazolidine into the ac...

Tautomerism plays a pivotal role in structural stabilization and reactivity. Herein we investigate in detail, aided by DFT simulations, the case of gossypol, a naturally-occurring atropisomeric dialdehyde showing promising properties as male contraceptive and antineoplasic agent. Its toxicity linked to reactive aldehydo groups can be reduced throug...

We report a combined experimental and computational study on the cycloadditions of bicyclic 1,3-thiazolium-4-olates, derived from thiazolidin-2-thiones, with asymmetrically-substituted acetylenes. These results provide further mechanistic insights into the above dipolar cycloadditions and enable an unequivocal characterization by NMR spectroscopy o...

We report a detailed investigation into the nature of products that are generated by the reactions of cyanamide and glyoxal, two small molecules of astrochemical and prebiotic significance, under different experimental conditions. The experimental data suggest that the formation of oligomeric structures is related in part to the formation of insolu...

The spontaneous loss of sulfur or isocyanate from transient 7-thia-2-azabicyclo[2.2.1]hept-5-en-3-ones, which are initially formed by 1,3-dipolar cycloadditions of thioisomünchnones with acetylenic dipolarophiles, is the key step in the chemoselective syntheses of pyridin-2-ones or thiophenes. The way by which sulfur is released has been the subjec...

This paper examines in detail the tautomerism of 2-aryl-substituted malondialdehydes, mainly focused on enolal structures, by means of gas-phase and solvent-based DFT calculations performed at the M06-2X/6-311++G(d,p) level. Open and pseudo-cyclic structures can be envisaged, the latter being decorated by an intramolecular hydrogen bond acting in s...

We revisit herein the formation and structure of dihydroxy dioxanes, which can be obtained from prebiotically available precursors and can be regarded as primeval sugar surrogates. Previous studies dealing with the heterogeneous composition of interstellar bodies point to the existence of significant amounts of small polyalcohols along with oxygen-...

Monoaza- and diaza-derivatives of malondialdehydes, in short aminoacroleins and vinamidines, are prototypical examples of open-chain structures prone to π-electron delocalization, for which intramolecular hydrogen bonding enhances (or diminishes) their pseudo-aromaticity depending on the substitution pattern. This interplay is illustrated herein by...

Mono- and diaza-derivatives of malondialdehydes, namely 3-alkyl(aryl)amino-2-arylacroleins and 1,5-dialkyl(aryl)-3-arylvinamidines are open-chain systems in which extended electron delocalization and pseudoaromaticity can be envisaged. A set of diversely functionalized compounds has been synthesized and characterized by spectroscopic data and X-ray...

This paper extends previous studies on hydrazones derived from hydroxyl naphthaldehydes to aromatic N-aminoheterocycles (exemplified herein by triazole derivatives), in an attempt to freeze enamine structures either by altering the electronic properties of the non-iminic nitrogen or through steric hindrance leading to coplanar dispositions between...

An improved preparation of mesoionic heterocycles 1,3-diazolium-4-thiolates by [3+2] cycloadditions of münchnones with aryl isothiocyanates is reported. The process takes place with high or complete regioselectivity, and fast and clean transformations are observed under microwave heating in DMF. DFT calculations support that this cycloaddition proc...

What accounts for a particular chiral selection in the case of a few sugars of prebiotic relevance, thereby mirroring the asymmetry observed in nature? By using first-principles calculations, the generation of pentoses from glycolaldehyde (the initial product of the autocatalytic formose reaction), which has been detected in outer space), has been...

a This manuscript describes an easy, accurate, and expeditious methodology to locate all the stationary points in common organic reactions. The protocol is based on the analysis of potential energy surfaces (PES) by fitting the calculated data to a mathematical function. The method has been tested in several organic reactions, especially cycloaddit...

Schiff bases derived from hydroxyl naphthaldehydes and o-substituted anilines have been prepared and their tautomerism assessed by spectroscopic, crystallographic, and computational methods. Tautomeric equilibria have also been studied and reveal in most cases a slight preference of imine tautomers in solution; a fact supported by DFT calculations...

Through a well-established enzymatic transformation glucosinolates release reactive isothiocyanates that can undergo further metabolic pathways affording a plethora of reactive metabolites. This study explores in detail the reaction of benzyl isothiocyanate, which possesses antitumor activity as alkylating agent, with d-glucosamine, commonly employ...

The azide-alkyne cycloaddition assisted by a self-assembled molecular flask developed by Rebek and coworkers (Org. Lett., 2002, 4, 327) has been simulated by means of the ONIOM methodology, thereby evidencing the reliability of this theoretical approach to model such large encapsulated systems. Experimental evidences accounting for this transformat...

Three Schiff bases generated by conventional condensation of a simple aminopolyol (TRIS) and 5-bromo- and 5-iodosalicylaldehyde, and 2-hydroxy-1-naphthaldehyde, have been fully characterized, both in solution and in the solid state. This study provides a complete analysis of imine–enamine equilibria, and sheds light onto the mechanism of hydrogen t...

Schiff bases derived from 2-hydroxy-1-naphthaldehyde, or 1-hydroxy-2-naphthaldehyde, and different saturated N-aminoheterocycles have been prepared. Their structures have been elucidated in both solution and the solid state, including unequivocal X-ray diffraction analyses. Experimental data evidence the presence of imine (or hydrazone) structures...

The archetypal Cu(I)-catalyzed alkyne-azide click cycloaddition (CuAAC) has been explored thoroughly via density functional calculations, modeling copper nuclei with the LANL2DZ basis set and aqueous environments with CPCM solvation. All the mechanistic proposals, ranging from the intermediacy of copper acetylides to π-complexes and multinuclear cl...

The conformational population of Z and E isomers of the amide bond in N-acetyl oxazolidines is dictated by the electronic nature of the vicinal aryl ring. Experimental and theoretical data support a rationale based on a strong and stereodirecting charge-charge interaction that should be added to the arsenal of non-covalent interactions and whose in...

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

The transformation of münchnones (mesoionic rings featuring the 1,3-oxazolium-5-olate core) into their sulfur counterparts (1,3-thiazolium-5-thiolates) by reaction with CS(2), pioneered by Huisgen and his group in the early 1970s, has been re-investigated in detail by means of both experimental and theoretical methods. The synthetic strategy can be...

Parity violation represents an essential property of particle and atomic handedness used to cope with the complex phenomenon of asymmetry in the universe. At the molecular level, however, numerous experiments suggest that parity-violating energy differences have not determined the amplification and propagation of homochirality. Asymmetric transform...

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

This paper describes the synthesis and structural elucidation of 1,3-oxazolidines derived from tris(hydroxymethyl)aminomethane (TRIS) and pyridine-based aldehydes. Divergent results were obtained with other formylpyridines, such aspyridoxal, in which intramolecular hydrogen-bonding largely stabilizes the iminic structure. The oxazolidines may under...

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

A series of oxazolidines derived from tris(hydroxymethyl)aminomethane (TRIS; 1), have been prepared efficiently. Geometries optimized at the B3LYP/6-31G* level of theory, along with the crystal data of compounds 9 and 12 and NOESY correlations, point to a strong endo anomeric effect that anchors a preferential conformation and subsequently dictates...

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Asymmetric tandem cycloaddition of a chiral carbohydrate nitroalkene with ethyl vinyl ether in the presence of electron-withdrawing alkenes produces a facile assembly of bicyclic systems, which can further be selectively cleaved to give homologated carbohydrates.

An intramolecular S(N)Ar mechanism has been identified in the unexpected aryl migration observed in a mesomeric betaine. The process changes drastically the optical and spectroscopic properties and should be a valuable model for related heteroaromatic systems.

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

This report revises and scrutinizes recent arguments, theories, and hypotheses related to the emergence of homochirality. Since the whole treatment would involve multiple and varied scenarios, emphasis is put only on some processes, believed (or claimed) to be prebiotically credible. A particular purpose is to introduce less-travelled paths in whic...

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

This paper describes a methodology that correlates experimental chemical shifts (at the alpha proton) of proteins with their geometrical data (both dihedral angles and distances) obtained from 13 representative proteins, which are taken from the Protein Data Bank (PDB) and the BioMagRes Data Bank (BMRB). To this end, the experimentally measured pro...

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

This paper documents in detail the reaction of 1,3-thiazolium-4-olates (thioisomunchnones) with aryl isothiocyanates. Having demonstrated with a chiral model that thionation occurs under these conditions to provide 1,3-thiazolium-4-thiolates and that this process is actually a stepwise domino reaction (J. Org. Chem. 2009, 74, 3698-3705), we extend...

Despite the comprehensive literature and enormous versatility of chiral imines derived from aminosugars and aldehydes, the corresponding counterparts generated from ketones remain an underestimated research subject. Filling in the gap, this manuscript sheds light on the synthetic and structural aspects of such substances and updates the few anteced...

Mesoionic heterocycles derived from 1,3-thiazolium-4-olates (thioisomunchnones) undergo thionation with aryl isothiocyanates to afford the corresponding 4-thiolate derivatives. Here, we document this transformation in detail, giving a crystallographic characterization of the solid-state structures. From the mechanistic viewpoint, the formal thionat...

A one-pot procedure for preparing chiral 1,3-oxazolidines derived from N-methyl-d-glucamine and aryl aldehydes is described. It has been carried out by using readily available reagents and operationally simple conditions allowing the preparation of the acyclic C-nucleoside analogs in high yields. The structure of these derivatives has been fully ch...

An unusual thionation strategy of mesoionic compounds with aryl isothiocyanates enables a facile synthesis of 1,3-thiazolium-4-thiolate systems. The mechanistic pathway of such a transformation most likely involves a stepwise 1,3-dipolar cycloaddition, which is supported by theoretical calculations performed with a two-layer hybrid method (B3LYP/6-...

A series of chiral imines derived from 1-amino-1-deoxyalditols such as d-glucamine, a rather unexplored raw material from the chiral pool, have been serendipitiously transformed into a novel family of N-acetyl-1,3-oxazolidines by means of an unexpected acetylation. The structure of these substances is supported by spectroscopic and crystallographic...

On the basis of our synthetic methodologies employing mesoionic synthons, the nucleophilic character of 2-alkyl-1,3-thiazolium-4-olates (2-alkylthioisomünchnones) has been envisaged and developed, at the expenses of their common role as masked 1,3-dipoles. Reactions with aliphatic acid chlorides lead to monoketones derived from thiazolidin-4-ones,...

Per-O-acetyl-β--glycopyranosylisothiocyanates (3 and 4) were condensed with 2-chloroethylamine hydrochloride to afford N,N'-bis(per-O-acetyl–β--glycopyranosyl)-N-(2-thiazolin-2-yl)thioureas (5 and 6) through the glycosylaminoheterocycles (7 and 8) as intermediates. Compounds 7 and 8 were converted into N-(2-thiazolin-2-yl)urea or thioureas (9–11) b...

A mesoionic acyclic C-nucleoside (4), serves as the starting chiron to construct highly functionalized 2-aza-7-thiabicyclo[2.2.1]heptanes and heptenes by means of a [3+2] cycloaddition with acetylenic and olefinic dipolarophiles. Further elimination of either sulfur or hydrogen sulfide leads to acyclic C-nucleosides bearing a heterocyclic moiety of...

A novel strategy, involving the coupling of enaminoesters with chlorosulfonyl isocyanate and accelerated by microwave irradiation, enables the straightforward preparation of the biologically important isoorotate bases. Extensions to nucleoside derivatives are also described.

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF.

Dass zwei Feststoffe eine Flüssigkeit bilden können, beobachtet man jeden Winter, wenn Salz auf vereiste Straßen gestreut wird. Beim Mischen bestimmter Feststoffe entstehen niedrig schmelzende und biologisch abbaubare Flüssigkeiten (siehe Bild). Diese eutektischen Mischungen eröffnen „grünere“ Alternativen zu herkömmlichen ionischen Flüssigkeiten u...

The present work describes a facile and practical route to carbohydrate-based isocyanates, a reactive and appealing family of chiral heterocumulenes, wich can be easily converted into disaccharides and pseudodisaccharides interconnected by urea moieties. A full characterization of these substances by X-ray diffraction analysis and spectroscopic met...

The present work describes in detail the preparation and structural characterization of a series of heteroaryls in which an o,o′-disubstituted phenyl ring is connected through a single C–N bond to a heterocyclic fragment of a chiral imidazolidine-2-one or 2-thione. As a consequence of hindered rotation, some of these substances exist as stable rota...

NMR spectroscopy has proven to be an enabling methodology in elucidating the axial chirality of a series of non-biaryl atropisomers attached to a carbohydrate moiety, based on deshielding effects caused by the aromatic ring.

The chemistry of mesoionic rings, especially their use as masked dipoles, has been a fruitful area of research since the late 1950s. With recent advances in the control of regio- and stereochemistry, the dipolar cycloaddition led to widespread application. In this Account, we illustrate our contribution employing thioisomünchnones, a class of mesoi...

In a record time the terms symmetry breaking and chiral symmetry breaking have gained a wide acceptance within the stereochemistry community. There has been a certain misuse of such terms as they are simply replacing well-established and unambiguous terms of the stereochemical glossary. Symmetry breaking is a useful and multifaceted concept that no...

In the light of recent and controversial findings on spontaneous resolution of racemates and their implications in the origin of homochirality on earth, we present here a detailed review of this important topic. Although spontaneous resolution cannot at this moment be reliably predicted, there has also been considerable progress in crystal structur...

This paper describes a general preparation of a series of 1,3-thiazolium-4-olates, each bearing an alkyl group at C-2, through reactions between N-arylthiocarboxamides and alpha-haloacyl halides. Unlike the 2-aryl-substituted derivatives, such alkylated mesoionic compounds exist in equilibria with their non-dipolar tautomers, the corresponding 2-al...

For Abstract see ChemInform Abstract in Full Text.

What does a Diels-Alder cycloaddition look like? This question is here addressed in the case of the increasingly significant cycloadditions of masked o-benzoquinones (MOBs), which serve as versatile dienes for the construction of complex and functionalized structures. So first, what the mechanism is not: It is not (by and large) a classical, concer...

For Abstract see ChemInform Abstract in Full Text.

A series of highly funtionalized beta-lactams and thiiranes can be generated on treatment of 1,3-thiazolium-4-olates (thioisomünchnones) with aliphatic aldehydes. Although in some cases a variety of products have been obtained, the present paper now provides a mechanistic rationale to explain the product distribution based on stereoelectronic effec...

This work describes the reactivity of 2-alkyl thioisomünchnones, exemplified here by the 2-methyl derivative, which behaves as nucleophile in the presence of both aliphatic and aromatic acid chlorides to give 2-heteroaryl ketones or 2-heteroaryl-1,3-diketones, respectively. However, 2-alkyl thioisomünchnones exhibit its characteristic 1,3-dipole be...

The magnetic deshielding caused by the amido group on CON-CHalpha protons of secondary amides can easily be correlated with DFT-based structures at the B3LYP/6-31G level of theory via a novel algorithm that refines previous models, such as the classical McConnell equation. The shift is given by delta = a + 2.16 cos2(alpha - 35)/d, where alpha denot...

Asymmetry at the level of elementary particles is both a wonder and a challenge. Current measurements of violation with respect to simultaneous space reflection and charge conjugation (CP violation) in the decay of B mesons appear to account for the excess of matter over antimatter. However, this particular decay can only be observed after a huge n...

A series of carbohydrate-based tetrahydropyridazines are prepared by the hetero-Diels-Alder reaction of the chiral 1,2-diaza-1,3-butadienes 1 and 2 with acrylonitrile. Reactions are regiospecific, and the observed diastereoselection is consistent with a preferred attack to the Re face of the heterodiene unit, as the chiral sugar placed at C4 does l...

The present contribution discloses a simple and unexpected acid-catalyzed cleavage of tetrahydrotetrazines leading to 1,2-bis(hydrazones). Incorporation of a chiral fragment derived from carbohydrates enables the rapid preparation of glycosazones, a family of compounds employed by Emil Fischer to elucidate the configuration of sugars. In addition,...

A mesoionic acyclic C-nucleoside 4, generated readily from δ-gluconolactone in a few synthetic steps, serves as the chiral core to construct a series of functionalized nucleosides bearing 2-aza-7-thiabicycle[2.2.1]heptane or 2-(1H)-pyridone moieties as the aglycon. The key step involves a [3+2] cycloaddition of 4 with several olefinic dipolarophile...

To what extent, if any, is the conformation of secondary amides revealed by theory? This question has now been addressed by computational methods using calculations at the B3LYP/6-31G* level of theory and 1 H NMR spectroscopy. Both gas-phase and solvent studies predict a Z-anti conformation to be the lowest in energy for an evaluated series of acet...

To what extent, if any, is the conformation of secondary amides revealed by theory? This question has now been addressed by computational methods using calculations at the B3LYP/6-31G level of theory and (1)H NMR spectroscopy. Both gas-phase and solvent studies predict a Z-anti conformation to be the lowest in energy for an evaluated series of acet...

Chiral dihydrothiophenes derived from carbohydrates can be transformed into a novel class of bicyclic and highly functionalized chirons by treatment with NaH. A mechanistic rationale is proposed which is consistent with experimental observations and demonstrates the stereodiscriminating properties exerted by carbohydrate chains with different confi...

This manuscript describes a one-pot, selective synthesis of optically active thiiranes by [3+2] cycloaddition of mesoionic dipoles with sugar aldehydes. Overall, the result is the formation of monosaccharide mimetics that display numerous functional groups for molecular recognition.

Dihydrothiophenes can easily be obtained by a general protocol involving the reaction of 2-aminothioisomünchnones with electron-deficient alkenes. The overall process can be interpreted as a sequential [3+2] cycloaddition/ring-opening cyclization reaction. The structures of the products could be unequivocally assigned by X-ray diffraction analysis....

2-Aminothioisomünchnones, a well-known family of masked dipoles, react with aromatic aldehydes in a domino cascade reaction that produces episulfides (thiiranes) or beta-lactams (2-azetidinones). This sequence is initiated by a [3+2] dipolar cycloaddition followed by ring opening of cycloadducts and intramolecular rearrangement to afford these unus...