Opening of Tartrate Acetals Using Dialkylboron Bromide: Evidence for Stereoselectivity Downstream from Ring Fission

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• 作者：Yvan Guindon ; William W. Ogilvie ; José ; e Bordeleau ; Wei Li Cui ; Kathy Durkin ; Vida Gorys ; Hé ; l&egrave ; ne Juteau ; René ; Lemieux ; Dennis Liotta ; Bruno Simoneau ; and Christiane Yoakim
• 刊名：Journal of the American Chemical Society
• 出版年：2003
• 出版时间：January 15, 2003
• 年：2003
• 卷：125
• 期：2
• 页码：428 - 436
• 全文大小：187K
• 年卷期：v.125,no.2(January 15, 2003)
• ISSN：1520-5126

文摘

Johnson-type acetals derived from dimethyl tartrate give, after opening with Me₂BBr and cupratedisplacement, secondary alcohols with high diastereoselectivity (>30:1). The mechanism proposed for theinduction of diastereoselectivity is downstream from the ring fission. It implies a direct participation of theLewis acid as a source of nucleophile and the stereospecific transformation of the resulting bromo acetalthrough an invertive and temperature-dependent process. The acetals are prepared by reaction of thedesired aldehyde with dimethyl tartrate. Removal of the auxiliary is accomplished through SmI₂ reductionor by an addition-elimination protocol using methoxide.