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Ir(I)-Catalyzed Enantioselective Decarboxylative Allylic Etherification of Aryl Allyl Carbonates 1 a
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Ir(I)-catalyzed enantioselective decarboxylative allylic etherification of aryl allyl carbonates provides aryl allyl ethers. Key to the generality and high stereoselection of the reaction is the use of the intramolecular decarboxylative allylation process and [Ir(dbcot)Cl](2) as an Ir(I) source. Ir(I)-catalyzed diastereoselective decarboxylative al...
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... temperatures for 24 h. These results, taken together with those in Tables 1 and 2, demonstrate the clear adven- tage of Ir-catalyzed enantioselective decarboxylative allylic etherification over the intermolecular counterpart. 16 To highlight a synthetic utility of the Ir(I)-catalyzed decarboxylative allylic etherification, we chose to synthe- size monoprotected 2-methyl-1,3-diols, which are common structural motifs in natural products. 17,18 Asymmetric crotylation of hydrocinnamaldehyde (13) by (R,R)-14 19 followed by cross-metathesis (CM) of the resulting ...
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Citations
... Decarboxylative C-O bond formation is a particularly attractive synthetic strategy since carboxylic acids are widely available in great structural diversity 4 . Thermal and photochemical strategies for decarboxylative C-O bond formation, including metalmediated oxidative decarboxylations using Mn III5, 6 , In III7 , Tl III8 , Pb IV9,10 or Ce IV11,12 , as well as precious metal-catalysed procedures such as Ru 13,14 , Ir 15,16 , Ag 17,18 or Au 19 , are relatively well developed. Photochemical reaction variants proceed under mild conditions but require expensive photocatalysts or prefunctionalised substrates (i.e. ...
... Pt was optimal as the anode material (entries [12][13][14]. A slight excess of HOBt was beneficial, whereas a larger excess of HOBt decreased the reaction rate and led to an insoluble coating of the anode as well as to benzotriazole formation (entries [15][16]. A reaction time of 30 min at room temperature and a constant current of 500 mA using Pt electrodes (2.0 × 1.0 cm) were found to be optimal (entries [17][18][19][20]. ...
Established electrodecarboxylative etherification protocols are based on Hofer-Moest-type reaction pathways. An oxidative decarboxylation gives rise to radicals, which are further oxidised to carbocations. This is possible only for benzylic or otherwise stabilised substrates. Here, we report the electrodecarboxylative radical-radical coupling of lithium alkylcarboxylates with 1-hydroxybenzotriazole at platinum electrodes in methanol/pyridine to afford alkyl benzotriazole ethers. The substrate scope of this electrochemical radical coupling extends to primary and secondary alkylcarboxylates. The benzotriazole products easily undergo reductive cleavage to the alcohols. They can also serve as synthetic hubs to access a wide variety of functional groups. This reaction prototype demonstrates that electrodecarboxylative C–O bond formation can be taken beyond the intrinsic substrate limitations of Hofer-Moest mechanisms. Since its discovery, the Hofer-Moest mechanism strongly limits the scope of electrochemical decarboxylative etherification. Here, the authors report the electrochemical conversion of carboxylic acids into alkyl benzotriazole ethers expanding the scope to primary and secondary acids beyond the boundaries of Hofer-Moest-type reactions.
Alongside enantioselective catalysis, synthetic chemists are often confronted by the challenge of achieving catalyst control over the relative configuration to stereodivergently access desired diastereomers. Typically, these approaches iteratively or simultaneously control multiple stereogenic units for which dual catalytic methods comprising sequential, relay, and synergistic catalysis emerged as particularly efficient strategies. In this Perspective, the benefits and challenges of catalyst-controlled diastereodivergence in the construction of carbon stereocenters are discussed on the basis of illustrative examples. The concepts are then transferred to diastereodivergent catalysis for atropisomeric systems with twofold and higher-order stereogenicity as well as diastereodivergent catalyst control over E- and Z-configured alkenes.
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