ChemInform Abstract: Enantioselective Prevost and Woodward Reactions Using Chiral Hypervalent Iodine(III): Switchover of Stereochemical Course of an Optically Active 1,3‐Dioxolan‐2‐yl Cation.

Abstract

Enantioselective Prevost and Woodward Reactions Using Chiral Hypervalent Iodine(III): Switchover of Stereochemical Course of an Optically Active 1,3-Dioxolan-2-yl Cation. -The reaction of alkenes (VI) with chiral hypervalent iodine reagent in the presence of acetic acid and the subsequent acetylation of the resulting regioisomeric mixture of monoacetylated products affords desired syn-diacetates (VII) with high diastereo-and enantioselectivities. The analogous reaction in the presence of acetic acid and trimethylsilyl acetate yields anti-diacetates (VIII). Similar switching of enantioselectivity can be achieved in related reactions of styrene derivatives (I). The intermediacy of a dioxolanyl cation is confirmed by trapping reaction with ketene silyl acetal [→ (XII)]. -(FUJITA*, M.; WAKITA, M.; SUGIMURA, T.; Chem. Commun. (Cambridge) 47 (2011) 13, 3983-3985, http://dx.doi.org/10.1039/c1cc10129c ; Grad. Sch. Mater. Sci., Univ. Hyogo, Ako, Hyogo 678, Japan; Eng.) -R. Staver