Ti/Pd Bimetallic Systems for the Efficient Allylation of Carbonyl Compounds and Homocoupling Reactions
作者:Alba Millán、Araceli G. Campaña、Btissam Bazdi、Delia Miguel、Luis Álvarez de Cienfuegos、Antonio M. Echavarren、Juan M. Cuerva
DOI:10.1002/chem.201003315
日期:2011.3.28
The allylation, crotylation and prenylation of aldehydes and ketones with stable and easily handled allylic carbonates is promoted by a Ti/Pd catalytic system. This Ti/Pd bimetallic system is especially convenient for the allylation of ketones, which are infrequent substrates in other related protocols, and can be carried out intramolecularly to yield five‐ and six‐membered cyclic products with good
Ti / Pd催化体系可促进醛和酮与稳定且易于处理的烯丙基碳酸酯的烯丙基化,丁酰化和烯丙基化。这种Ti / Pd双金属体系特别适合于酮的烯丙基化,酮是其他相关规程中不常见的底物,并且可以在分子内进行生产,从而产生具有良好立体选择性的五元和六元环状产物。此外,Ti / Pd介导的还原反应和Würtz型二聚反应可以很容易地从碳酸烯丙酯和羧酸酯中进行。
Regio- and Stereoselective Synthesis of 1,5-Dienes Using Allylic Barium Reagents
The highly α,α′ selective and stereocontrolled homocoupling reaction of allylic halides was achieved using barium reagent. The double-bond geometry of the starting allylic chloride was completely retained. The α,α′ cross-coupling products were also prepared stereospecifically and regioselectively by this method.
Reactions of geranyl and farnesyl halide, and their geometricalisomers with chlorotris(triphenylphosphine)cobalt(I) gave the corresponding geometrically pure coupling products under mild and non-basic conditions. Squalenes were stereospecifically synthesized by this method.
Allylicacetates were coupled with zinc dust in the presence of a catalytic amount of [Pd(PPh3)4] to give the corresponding 1,5-dienes under mild conditions in high yields. Significant co-solvent effects were found with methanol or 1,2-ethanediol in tetrahydrofuran.
The reaction of allylic acetates with zinc in the presence of a catalytic amount of hexacarbonylmolybdenum(0) led to reductive coupling for the formation of a 1,5-diene framework. Reductive coupling of nerolidyl acetate provided squalene and its isomers in high yield.