Mutter R, Campbell I B, Martin De La Nava E M, Merritt A T, Wills M
Department of Chemistry, University of Warwick, Coventry CV4 7AL, U.K.
J Org Chem. 2001 May 18;66(10):3284-90. doi: 10.1021/jo0011991.
The palladium-catalyzed reaction of pinacolone with tert-butyldimethyl(3-(2-bromophenyl)allyloxy)silane results in direct formation of 1-vinyl-3-tert-butyl-1H-isochromene. This is the result of a ketone arylation followed by an intramolecular cyclization of the enolate with the allylic system. The use of a lithium diamide base appears to be essential for success. The tert-butyldimethylsilyl protecting group is also an essential choice as it furnishes the appropriate reactivity to promote allylic substitution after the aryl coupling process. The use of more effective leaving groups, such as acetate, results in reaction of the allylic group, and no aryl coupling is observed. Through the appropriate selection of phosphine ligand and solvent, either the cyclized isochromene product or the noncyclized intermediate may be formed selectively. A short combinatorial study of the scope and limitations of the reaction, involving 24 ketones, is described.
频哪酮与叔丁基二甲基（3 - （2 - 溴苯基）烯丙氧基）硅烷在钯催化下反应直接生成1 - 乙烯基 - 3 - 叔丁基 - 1H - 异苯并呋喃。这是酮芳基化反应后烯醇盐与烯丙基体系发生分子内环化反应的结果。使用二酰胺锂碱似乎是反应成功的关键。叔丁基二甲基硅基保护基也是一个必不可少的选择，因为它能提供适当的反应活性，以促进芳基偶联反应后烯丙基取代反应的进行。使用更有效的离去基团，如乙酸根，会导致烯丙基发生反应，且未观察到芳基偶联反应。通过适当选择膦配体和溶剂，可以选择性地形成环化的异苯并呋喃产物或未环化的中间体。本文描述了一项涉及24种酮的反应范围和局限性的简短组合研究。
