Synthesis of Highly Substituted Racemic and Enantioenriched Allenylsilanes via Copper-Catalyzed Hydrosilylation of (<i>Z</i>)-2-Alken-4-ynoates with Silylboronate
Copper-catalyzed highly efficient hydrosilylation reaction of enynoates was developed. Under simple reaction conditions, various di-, tri-, and tetrasubstituted racemic allene products could be obtained in high yields. The asymmetric 1,6-addition of silyl group to the (Z)-2-alken-4-ynoates could be achieved under mild reaction conditions to afford the silyl-substituted enantioenriched chiral allene
reactivity of alkoxycarbonyl- and cyanoenynes in the homo-benzannulation of conjugatedenynes. The introduction of these electron-withdrawing groups enabled us to carry out the benzannulation of 1-substituted enynes as well as 1,2- and 2,4-disubstituted enynes, which have much lower reactivity compared to 2- or 4-monosubstituted enynes. Polysubstituted benzenes were prepared in a highly regioselective manner
Regioselective Synthesis of (E)-5-(Tributylstannylmethylidene)-5H-furan-2-ones and (E)-3-(Tributylstannylmethylidene)-3H-isobenzofuran-1-ones: Easy Access to γ-Alkylidenebutenolide and Phthalide Skeletons
Regio- and stereoselective synthesis of γ-alkylidenebutenolides and γ-alkylidenephthalides has been achieved through the palladium-catalysed tandem cross-coupling/cyclisation reactions of tributylstannyl-3-iodopropenoate or the 2-iodo benzoate derivatives with tributyltinacetylene. Iododestannylation occurred with inversion of the configuration of the exocyclic double bond in the case of butenolides, but with retention of configuration for the phthalide. The selectivity observed in the Stille reaction was found to be dependent on the nature of the vinyl or the aryl halide.
Palladium-iminophosphine complex catalyzes stannylative cycloaddition of conjugated enynes using hexabutyldistannoxane as a stannylating agent to afford highly substituted 3-alkenylphenylstannanes regioselectively. Stannylative cross-cycloaddition reactions between different enynes or between enynes and diynes are also achieved. The reaction is successfully applied to a concise synthesis of alcyopterosin N, which has been isolated recently from sub-Antarctic soft coral, Alcyonium paessleri.
Dess−Martin Periodinane Oxidation of Alcohols in the Presence of Stabilized Phosphorus Ylides: A Convenient Method for the Homologation of Alcohols via Unstable Aldehydes
作者:Anthony G. M. Barrett、Dieter Hamprecht、Mitsuru Ohkubo