Chelates as intermediates in nucleophilic additions to alkoxy ketones according to Cram's rule (cyclic model)

X Chen, ER Hortelano, EL Eliel…

Index: Chen, Xiangning; Hortelano, Edwin R.; Eliel, Ernest L.; Frye, Stephen V. Journal of the American Chemical Society, 1992 , vol. 114, # 5 p. 1778 - 1784

Full Text: HTML

Citation Number: 141

Abstract

Abstract: Chelates have been considered intermediates in the often highly stereoselective reactions of a-alkoxy and similarly substituted ketones for over 30 years, I0 but without mechanistic evidence. It is now shown, by stop-flow (“rapid injection”) NMR kinetics,'5 that the swific rates of reaction of ketones C6H5COCH (OR) CH3 with MQMg, where R=(i-Pr) $ i (“TIPS”), t-BuPh $ i, t-BuMe2Si, Et& Me&, and Me, parallel the diastereoselectivity of the ...