Enzyme‐ and Ruthenium‐Catalyzed Enantioselective Transformation of α‐Allenic Alcohols into 2,3‐Dihydrofurans

Highly enantioselective syntheses of homopropargylic alcohols and dihydrofurans catalyzed by a bis(oxazolinyl)pyridine-scandium triflate complex.

Lewis acid promoted reactions of allylsilanes and allenylsilanes provide access to important building blocks for natural product synthesis.1 For example, trimethylsilylallenes function as propargylic anion equivalents in aldehyde addition reactions (eq 1, Path A).2 If the silicon center is sterically congested, the normal addition pathway is suppressed and functionalized dihydrofurans are produ...

Ruthenium-catalyzed enantioselective propargylation of aromatic compounds with propargylic alcohols via allenylidene intermediates.

Functionalized 2,3-dihydrofurans via palladium-catalyzed oxyarylation of α-allyl-β-ketoesters.

The palladium-catalyzed reaction of (hetero)aryl bromides, chlorides, and nonaflates with α-allyl-β-ketoesters provides ready efficient access to functionalized 2,3-dihydrofurans. The reaction tolerates several useful substituents including chloro, fluoro, ether, ketone, ester, cyano, and nitro groups.

CuCl-catalyzed aerobic oxidation of 2,3-allenols to 1,2-allenic ketones with 1:1 combination of phenanthroline and bipyridine as ligands

A protocol has been developed to prepare 1,2-allenyl ketones using molecular oxygen in air or pure oxygen as the oxidant from 2,3-allenylic alcohols with moderate to good yields under mild conditions. In this reaction CuCl (20 mol %) with 1,10-phenanthroline (10 mol %) and bipyridine (10 mol %) was used as the catalyst. It is interesting to observe that the use of the mixed ligands is important...

Ruthenium-catalyzed asymmetric hydrogenation of N-boc-indoles.

Highly enantioselective hydrogenation of various N-Boc-indoles proceeded successfully in the presence of the ruthenium complex generated from an appropriate ruthenium precursor and a trans-chelate chiral bisphosphine PhTRAP. Various 2- or 3-substituted indoles were converted into chiral indolines with high enantiomeric excesses (up to 95% ee). The PhTRAP-ruthenium catalyst was able to promote t...