Studies on the Mechanism of the [3+2] Annulation Based on the Brook Rearrangement

基于Brook重排的[3 2]成环机制研究

基本信息

批准号：
08672416
负责人：
TAKEDA Kei
金额：
$ 1.41万
依托单位：
TOYAMA MEDICAL AND PHARMACEUTICAL UNIVERSITY
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
1996
资助国家：
日本
起止时间：
1996 至 1997
项目状态：
已结题

项目摘要

Product distributions in the reactions of beta-heteroatom-substituted acryloylsilanes with ketone enolates, which was used in [3+2] annulation for preparation of functionalized cyclopentenols, highly depend upon the beta-substituent. Thus, in contrast to the observation with (E)- and (Z)-beta-phenylthio derivatives in which isomeric cyclopentenols were obtained in almost same ratio irrespective of the acylsilane geometry, the trimethylsilyl derivative afforded a single cyclopentenol and uncyclized enolsilyl ether in the ratio depending on the vinylsilane geometry. In order to rationalize these results, we postulated a reaction course which involves two compet-ing pathways depending of the alpha-carbanion-stabilizing ability of the beta-substituents in the acryloylsilane ; (a) intramolecular aldol reaction of delocalized allylic anion in termediate, Brook rearrangement product of 1,2-adduct, and (b) oxyanion-accelerated vinylcyclopropane rearrangement of cylcopropanolate which is derived from the 1,2-adduct via Brook rearrangement/cyclopropanation sequence. To get support to this proposal, we compared alpha-carbanion-stabilizing ability of the phenythio and the trimethylsilyl groups using the reactions of the acryloylsilanes with lithium enolate to t-butyl acetate, providing 1,2-addition product and Brook rearrangement/allylic rearrangement product in the ratio reflecting the difference of alpha-carbanion stabilizing ability of the b-substituent. And we examined low-temperature oxyanion accelerated vinylcyclo-propane-cyclopentene rearrangement using the reaction of four isomeric vinylcyclopropyl acetates with MeLi (2.2eq), affording the cyclopentenol and the uncyclized enol silyl ether in the ratio depending on the vinylsilane geometry.

β-杂质素取代的丙烯酰基与酮烯醇的反应中的产物分布，该丙烯烯烯烯在[3+2]环中用于制备官能化环戊烯醇，高度取决于β-屈服者。 Thus, in contrast to the observation with (E)- and (Z)-beta-phenylthio derivatives in which isomeric cyclopentenols were obtained in almost same ratio irrespective of the acylsilane geometry, the trimethylsilyl derivative afforded a single cyclopentenol and uncyclized enolsilyl ether in the ratio depending on the vinylsilane geometry.为了使这些结果合理化，我们假设了一个反应过程，该过程涉及两种竞争途径，具体取决于乙酰基硅烷中β-取代物的α-碳化稳定能力；（a）在定期的，布鲁克的1,2添加剂和（b）cylcopropanter的氧化乙烯基乙烯基乙丙烷的重排的定位，布鲁克重排产物中的分子内醛醇反应，该甲基甲基甲酸的乙烯基乙烯基甲基甲基甲基甲酸甲酸甲基甲基甲酸甲酸甲基甲基甲酸的重排，这些乙烯基甲酸重排，这些乙烯基甲酸重新排列，这些乙烯基甲基甲基甲基甲酸的重新构造是通过Brook Adduct/cyclopropopanation corence corence cor。为了获得这一建议，我们使用丙烯酰基与锂烯丙基烷酸酯的反应与乙酸二丁酯的反应进行了比较了苯第苯甲烷和三甲基甲硅烷基群体的α-稳定能力，从而提供了1,2-附加产品，并提供了1,2-附加产品的稳定能力，并在稳定的稳定性稳定性稳定性的稳定性均可在反映的速率上反映出比率的分别是反映的比率。 b-substitunt。我们使用四种异构体乙烯基乙烯基丙烷基乙酸盐与MELI（2.2EQ）的反应，检查了低温氧气加速乙烯基乙烯基丙烷 - 丙烷 - 环烯烯的重排，从而使环戊烯醇和未确定的Enol silyl silyl乙基醚在乙烯烯基质量上依赖于乙烯烯。