Enantioselective Total Synthesis of (+)-Cassiol

An enantioselective total synthesis of (+)-cassiol is reported. The complex derived from Pd-2(pmdba)(3) and enantiopure t-BuPHOX ligand catalyzes enantioconvergent decarboxylative alkylation to generate the quaternary carbon stereocenter at an early stage. The overall synthetic strategy involves a convergent late-stage coupling of two fragments. The synthesis features a longest linear sequence of eight steps

Enantioselective Tsuji Allylations

The family of allylation reactions developed by Tsuji in the 1980s are capable of generating tertiary and quaternary carbon stereocenters from several synthetic precursors. Despite the utility of these transformations, they have seen little use in the synthesis of natural products. Recently, the power of these reactions was significantly enhanced by the development of enantioselective versions of these transformations. Applications of these methods to the enantioselective syntheses of natural products and pharmaceutical compounds highlight the importance of these developments

Preparation of (S)-2-Allyl-2-methylcyclohexanone (Cyclohexanone, 2-methyl-2-(2-propen-1-yl)-, (2S)-)

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Catalytic Enantioselective Decarboxylative Protonation

We report a highly enantioselective, general catalytic system for the facile synthesis of tertiary stereocenters by protonation adjacent to cyclic ketones. The method relies on catalytic decarboxylative protonation of readily accessible racemic quaternary β-ketoesters. A range of substituted cycloalkanone compounds can be accessed through this process with high levels of enantioselectivity

Homogeneous Pd-Catalyzed Enantioselective Decarboxylative Protonation

General homogeneous conditions for the palladium-catalyzed synthesis of carbonyl compounds with tertiary carbon stereocenters at the α-position are reported. The highly reactive catalyst tolerates a variety of substrate substitution and functionality, and generates enantioenriched cyclic ketones from racemic allyl β-ketoester starting materials

Short Enantioselective Formal Synthesis of (–)-Platencin

A short enantioselective formal synthesis of the antibiotic natural product platencin is reported. Key steps in the synthesis include enantioselective decarboxylation alkylation, aldehyde/olefin radical cyclization, and regioselective aldol cyclization

Preparation of (S)-tert-ButylPHOX (Oxazole, 4-(1,1-dimethylethyl)-2-[2-(diphenylphosphino)phenyl]-4,5-dihydro- (4S)-)

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Enantioselective protonation

Enantioselective protonation is a common process in biosynthetic sequences. The decarboxylase and esterase enzymes that effect this valuable transformation are able to control both the steric environment around the proton acceptor (typically an enolate) and the proton donor (typically a thiol). Recently, several chemical methods for achieving enantioselective protonation have been developed by exploiting various means of enantiocontrol in different mechanisms. These laboratory transformations have proved useful for the preparation of a number of valuable organic compounds. Here, we review recent reports of enantioselective protonations, classifying them according to mechanism, and discuss how a deeper understanding of the processes can lead to improved methods for effecting this most fundamental method of obtaining enantiopure compounds