The exocyclic effect: protecting group strategy to enhance stereoselectivity in hydrogen transfer reactions of acyclic free radicals

摘要

To enhance the diatereoselectivity of the hydrogen transfer reaction of acyclic substrates bearing 1,2- or 1,3-diols, the feasibility of a strategy employing bifunctional protecting groups have been demonstrated. This strategy is based upon the "exocyclic effect" or the significant improvement of nti-selectivity exhibited by the reductions of substrates in which the two substituents (R_1 and Y) at the stereogenic center α to the radical center are linked together.