Radical Cyclization vs. Elimination in the Vitamin-B₁₂-Catalyzed Reduction of Unsaturated Bromo Acetals and Bromo Orthoesters

Kazumasa Yamamoto; Stefan Abrecht; Rolf Scheffold

doi:10.2533/chimia.1991.86

Radical Cyclization vs. Elimination in the Vitamin-B₁₂-Catalyzed Reduction of Unsaturated Bromo Acetals and Bromo Orthoesters

Authors

Kazumasa Yamamoto
Stefan Abrecht
Rolf Scheffold

DOI:

https://doi.org/10.2533/chimia.1991.86

Abstract

Reduction of the 2-bromoacetaldehyde acetals of cinnamyl alcohol or propargyl alcohol with Zn/NH₄ in presence of catalytic amounts of B₁₂ in DMF affords oxolanes by free radical 5-exo-cyclization and the corresponding alcohols by reductive elimination. 2-(Bromoethyl) dimethyl orthopropiolate mainly decomposes by reductive elimination and by hydrogenolysis of the bromide.