Stereoselective epoxidation of cyclic alkenes using m-CPBA and Oxone®/trifluoroacetone — A comparison
作者:Simon E. de Sousa、Peter O'Brien、Christopher D. Pilgram、Daniel Roder、Timothy D. Towers
DOI:10.1016/s0040-4039(98)02320-x
日期:1999.1
A comparison of the observed diastereoselectivity of epoxidation of cyclic alkenes using m-CPBA and Oxone®/trifluoroacetone is reported. The results indicate that dioxiraneepoxidations are sterically controlled and provide a crude model for determination of whether hydrogen bonding is operating in the m-CPBA epoxidations.
Unexpected effect of protecting group and solvent on the stereoselectivity of m-CPBA epoxidation of diprotected cis-4,5-dihydroxycyclohexenes
作者:Simon E. de Sousa、Alex Kee、Peter O'Brien、Simon T. Watson
DOI:10.1016/s0040-4039(98)02319-3
日期:1999.1
The stereoselectivity of m-CPBA epoxidation of diprotected cis-4,5-dihydroxycyclohexenes has been studied as a function of protecting group. solvent and in one example, epoxidising reagent. Three different ways of obtaining high levels of trans diastereoselectivity have been uncovered. In addition, the results suggest that bulky silyl protecting groups (eg triethylsilyl and tert-butyldimethylsilyl) can, in CH2Cl2, behave as moderate cis-directors via hydrogen bonding to m-CPBA. (C) 1998 Elsevier Science Ltd. All rights reserved.