On the relation between ring size and geometry of 2-bromo-2-cycloalkenyl acetates formed from dibromobicyclo[n.1.0]alkanes by silver acetate-catalyzed reactions. Use of 3J(C-H) couplings to assign the geometry of trisubstituted olefins

Exploitation of Cyclopropane Carbaldehydes to Prins Cyclization: Quick Access to ( E)-Hexahydrooxonine and Octahydrocyclopenta[ b]pyran

A single-step TiX₄-mediated Prins-type cyclization of cyclopropane carbaldehydes with 3-buten-1-ol for the highly stereoselective construction of relatively strained ( E)-hexahydrooxonines is reported. Switching the alcohol to 3-butyn-1-ol prompted a similar route, augmented by another cyclization within a nine-membered ring to afford a bicyclized product (4,4-dihalo-5-aryloctahydrocyclopenta[ b]pyran). Easy transformation of the resulting geminal dihalide to a vinyl halide and a ketone further supplemented the substance of this approach.