Asymmetric synthesis of chiral β-alkynyl carbonyl and sulfonyl derivatives via sequential palladium and copper catalysis

Regiodivergent Hydrosilylation of Polar Enynes to Synthesize Site-Specific Silyl-Substituted Dienes

Herein, we present catalyst-regulated switchable site-selective hydrosilylation of enynes, which are suitable for a wide range of alkyl and aryl substituted polar enynes and exhibit excellent functional group compatibility. Under the optimized conditions, silyl groups can be precisely installed at various positions of 1,3-dienes. While α- and γ-silylation products were obtained under platinum-catalytic systems, β-silylation products were delivered with [Cp*RuCl]4 as catalyst. This process lead to the formation of 1,3-dienoates with diverse substitutions, which would pose challenges with other methodologies.

Synthesis of the Marine Alkaloid Cylindricine C and Serendipitous Synthesis of Its 2,13-Di-epi Stereoisomer

A new approach to the marine alkaloid cylindricine C afforded its previously unreported (±)-2,13-di-epi stereoisomer as the major product along with a minor amount of the racemic parent alkaloid. Key steps included a stereoselective dianion alkylation of a monoester of 1,2-cyclohexanedicarboxylic acid and an annulation based on the tandem conjugate addition of a primary amine to an acetylenic sulfone, followed by intramolecular acylation of the resulting sulfone-stabilized carbanion. The cis-azadecalin moiety thus formed, comprising the cyclohexane A-ring and enaminone B-ring of the products, was further elaborated by the selenenyl chloride-induced cyclofunctionalization of a pendant butenyl substituent with the enaminone moiety, followed by a seleno-Pummerer reaction. Desulfonylation and enaminone reduction afforded the final products. Molecular modeling and X-ray crystallography provided further insight into these processes.

Ene-Reductase: A Multifaceted Biocatalyst in Organic Synthesis

Biocatalysis integrate microbiologists, enzymologists, and organic chemists to access the repertoire of pharmaceutical and agrochemicals with high chemoselectivity, regioselectivity, and enantioselectivity. The saturation of carbon-carbon double bonds by biocatalysts challenges the conventional chemical methodology as it bypasses the use of precious metals (in combination with chiral ligands and molecular hydrogen) or organocatalysts. In this line, Ene-reductases (ERs) from the Old Yellow Enzymes (OYEs) family are found to be a prominent asymmetric biocatalyst that is increasingly used in academia and industries towards unparalleled stereoselective trans-hydrogenations of activated C=C bonds. ERs gained prominence as they were used as individual catalysts, multi-enzyme cascades, and in conjugation with chemical reagents (chemoenzymatic approach). Besides, ERs' participation in the photoelectrochemical and radical-mediated process helps to unlock many scopes outside traditional biocatalysis. These up-and-coming methodologies entice the enzymologists and chemists to explore, expand and harness the chemistries displayed by ERs for industrial settings. Herein, we reviewed the last five year's exploration of organic transformations using ERs.

Copper-Catalyzed Cascade Aminoalkynylation-Oxidation of Propargylic Alcohols: Stereospecific Synthesis of ( Z)-2-Amino Conjugated Enynals/Enynones

Copper-catalyzed cascade aminoalkynylation-oxidation of propargylic alcohols has been realized, sterospecifically providing an array of ( Z)-2-amino conjugated enynals/enynones in good yields under mild conditions. This transformation involves a rare 1,3-alkynyl migration of propargylic alcohols and simultaneously forms C-C, C-N, and C═O bonds. Furthermore, ( Z)-2-amino conjugated enynals were applied to efficiently synthesize 3,5-disubstituted-1 H-pyrrole-2-carbaldehyde and conjugated enynol derivatives.

Iridium-catalysed conjugated alkynylation of α,β-unsaturated amide through alkene isomerization

We have developed an iridium-catalysed conjugated alkynylation of α,β-unsaturated amide.