Stereoselective Carbocyclization of Vinyloxiranes Catalyzed by Lewis Acids: Construction of the Musellarin Tricyclic Core

Abstract

Stereoselective carbocyclizations of vinyloxiranes were efficiently catalyzed by Lewis acids to provide cyclic homoallyl alcohols as single isomers. The choice of Lewis acid, B(C6F5)3 was crucial for the stereoselective transformation in the case of cis vinyloxiranes, whereas BF3∙OEt2 was proven to be an effective catalyst for trans substrates. The method was well implemented in the synthesis of seven‐membered rings and six‐membered rings with functional group tolerance. Utility of the resulting trans‐ and cis homoallyl alcohols was demonstrated to concisely build the tricyclic core of musellarin A and E.

Additive-free oxychlorination of unsaturated C–C bonds with tert-butyl hypochlorite and water

“…With regard to the functionalization of alkenes, one of the issues that needed to be taken into account is the Z - or E -selectivity. 20 With respect to alkene chlorohydroxylation in previous publications, a direct comparison of and the rational behind diasteroselectivity between the geometrical isomers have been much less-studied. As shown in Scheme 2, only benzylic alcohol products were observed irrespective of the geometry of the alkenes, obeying the Markovnikov rule in electrophilic addition.…”