Ynolates were found to react with alpha-alkoxy-, alpha-siloxy-, and alpha-aryloxyketones at room temperature to afford tetrasubstituted olefins with high Z selectivity. Since the geometrical selectivity was determined in the ring opening of the beta-lactone enolate intermediates, the torquoselectivity was controlled by the ethereal oxygen atoms. From experimental and theoretical studies, the high Z
By treatment with stabilized lithium phosphonates in the presence of activated 4Å molecular sieves, unprotected α-hydroxy ketones 1 undergo a convenient Horner-Wadsworth-Emmonsolefination to give directly butenolides 3 as exclusive or predominant products.
Reaction Of β,γ-Unsaturated Carboxylic Acids With Thallium Triacetate (Tta): Lactonization<i>VS</i>Oxidative Decarboxylation
作者:Helena M. C. Ferraz、Mčnica V. A. Grazini、Luiz F. Silva、Luiz S. Longo
DOI:10.1080/00397919908086184
日期:1999.6
Abstract The reaction of six β,γ-unsaturated carboxylic acids with thalliumtriacetate (TTA) was studied. The nature of the products is highly sensitive to the substitution pattern of the substrates. Aliphatic acids gave mainly lactones, while those bearing an aromatic ring furnished only decarboxylation products.
A direct and selective synthesis of α,β-unsaturated piperidones by a new palladium-catalyzed cascade carbonylation is described. In the presented protocol, easily available propargylic alcohols react with aliphatic amines to provide a broad variety of interesting heterocycles. Key to the success of this transformation is a remarkable catalytic cleavage of the present carbon–carbon triple bond by using