Christopher Golz's research while affiliated with Georg-August-Universität Göttingen and other places

The regioselective functionalization of heptacyclo[6.6.0.02,6.03,13.04,11.05,9.010,14]tetradecane (HCTD) under photocatalytic conditions is described. The protocols developed share an initial photo‐triggered hydrogen atom abstraction that regioselectively generates the necessary HCTD‐radical preferentially at position 1‐, they employ no excess of the precious cage carbocycle, and enable the straightforward access to a broad variety of 1‐(alkyl, aryl, or sulfinyl) HCTDs in moderate but still synthetically useful yields. The scope and limitations of each transformation are also discussed.

The synthesis of (±)-angustatin A, a phenanthrene-containing cyclophane that possesses conformational chirality, is reported. Key steps include a Pd-catalyzed Negishi coupling to assemble the necessary terphenyl intermediate, its closure into a 14-membered macrocycle via a catalytic-in-phosphine Wittig olefination, and finally a Pt-catalyzed alkyne hydroarylation, which is able to assemble the phenanthrene unit despite the thermodynamic cost of significantly bending arene A from the ideal plane.

Saturated bridged-bicyclic compounds are currently under intense investigation as building blocks for pharmaceutical drug design. However, the most common methods for their preparation only provide access to bridgehead-substituted structures. The synthesis of bridge-functionalised species is highly challenging but would open up many new opportunities for molecular design. We describe a photocatalytic cycloaddition reaction that provides unified access to bicyclo[2.1.1]hexanes with 11 distinct substitution patterns. Bridge-substituted structures that represent ortho-, meta-, and polysubstituted benzene bioisosteres, as well as those that enable the investigation of chemical space inaccessible to aromatic motifs can all be prepared using this operationally simple protocol. Proof-of-concept examples of the application of the method to the synthesis of saturated analogues of biorelevant trisubstituted benzenes are also presented.

The evaluation of the pentafluorocyclopropyl group as a chemotype in crop protection and medicinal chemistry has been hampered in the past by the lack of suitable methodologies that enable the practical incorporation of this moiety into advanced synthetic intermediates. Herein, we report the gram‐scale synthesis of an unprecedented sulfonium salt, 5‐(pentafluorocyclopropyl)dibenzothiophenium triflate, and its use as a versatile reagent for the photoinduced C−H pentafluorocyclopropylation of a broad series of non‐previously functionalized (hetero)arenes through a radical mediated mechanism. The scope and potential benefits of the protocol developed are further demonstrated by the late‐stage introduction of the pentafluorocyclopropyl unit into biologically relevant molecules and widely used pharmaceuticals.

The evaluation of the pentafluorocyclopropyl group as a chemotype in crop protection and medicinal chemistry has been hampered in the past by the lack of suitable methodologies that enable the practical incorporation of this moiety into advanced synthetic intermediates. Herein, we report the gram‐scale synthesis of an unprecedented sulfonium salt, 5‐(pentafluorocyclopropyl)dibenzothiophenium triflate, and its use as a versatile reagent for the photoinduced C−H pentafluorocyclopropylation of a broad series of non‐previously functionalized (hetero)arenes through a radical mediated mechanism. The scope and potential benefits of the protocol developed are further demonstrated by the late‐stage introduction of the pentafluorocyclopropyl unit into biologically relevant molecules and widely used pharmaceuticals.

Boron-based dipyrrin chromophores (BODIPY) have found widespread application over the last twenty years in fields as diverse as medicine and materials. Thus, several efforts have been placed to exchange boron with other elements, with the aim of developing materials with complementary luminescent properties. However, despite these attempts, the incorporation of other main-group elements in dipyrrin scaffolds remains still rare. We have successfully synthesized and characterized novel chromophores based on antimony and bismuth, SBDIPY and BIDIPY. Solution stabilities have been investigated by VT-UV/vis spectroscopy and the fluorescence emission studied and supported by computational analysis. We were also able to isolate the first direct analogue of BODIPY containing fluoride handles, disclosing preliminary luminescent features.

A series of helically‐shaped benzo[b]chryseno[4,3‐d]thiophenes, naphtho[1,2‐b]phenanthro[4,3‐d]thiophenes and chryseno[3,4‐b]naphtho[1,2‐d]thiophenes are synthesized via a highly enantioselective Au‐catalyzed intramolecular alkyne hydroarylation reaction. The inversion barriers of the structures obtained are determined both theoretically and experimentally, and their chiroptical properties reported. Preliminary studies on the post‐synthetic functionalization of these thiahelicenes, and their transformation into azahelicenes are also presented. In addition, a straightforward one‐step protocol is developed, which wraps the initially obtained chryseno[3,4‐b]naphtho[1,2‐d]thiophenes into bowl‐shaped pleiadene derivatives without erosion of the enantiopurity. The number of structurally related products that are obtained with high enantioselectivity enables the establishment of comprehensive correlations between the structure and conformational stability or (chir)optical properties. This article is protected by copyright. All rights reserved

This manuscript reports the synthesis and structure of an unprecedented sulfonium salt, 5‐(trifluorovinyl)dibenzothiophenium triflate, and its use as a versatile reagent for the introduction of the bioisosteric 1,1,2‐trifluoroethylene linker in drug‐like structures. The protocol developed consists of the reaction of this compound with alcohols and phenols to deliver a complete set of 1,2,2‐trifluoro‐2‐(alkoxy‐/aryloxy)ethyl sulfonium salts, which have been purified by column chromatography and fully characterized. Subsequent single electron reduction under mild photochemical conditions efficiently affords the corresponding fluoroalkyl radicals that are trapped either intra‐ or intermolecularly through their reaction with (hetero)arenes. Theoretical calculations are used to evaluate the conformational consequences derived from the presence of the CF2‐CHF tether.

A visible‐light organophotocatalytic [2+2] cycloaddition of electron‐deficient styrenes is described. Photocatalytic [2+2] cycloadditions are typically performed with electron‐rich styrene derivatives or α,β‐unsaturated carbonyl compounds, and with transition‐metal‐based catalysts. We have discovered that an organic cyanoarene photocatalyst is able to deliver high‐value cyclobutane products bearing electron‐deficient aryl substituents in good yields. A range of electron‐deficient substituents are tolerated, and both homodimerisations and intramolecular [2+2] cycloadditions to fused bicyclic systems are available by using this methodology.

A Au‐catalyzed protocol for the enantioselective synthesis of molecular architectures containing an internal [5]helicene and two peripherical axial stereogenic elements is described. While the diasteroselectivity of the double alkyne hydroarylation sequence is not optimal, and mixtures that contain similar amounts of two of the four possible diasteromeric products are obtained (one C2 and one non‐symmetric), the assembly of the C2‐symmetric isomer often occurs with high enantioselectivity (up to 98 % ee). The absolute configurations of the products obtained were determined by X‐ray crystallography. Studies on the thermal racemization of the internal [5]helicene moiety in the C2‐symmetric isomers determined the half‐life of this element to be approximately 3 h at 50 °C.