Tuning the Reactivity of Oxygen/Sulfur by Acidity of the Catalyst in Prins Cyclization: Oxa- versus Thia-Selectivity
作者:B. V. Subba Reddy、A. Venkateswarlu、Prashant Borkar、J. S. Yadav、B. Sridhar、René Grée
DOI:10.1021/jo402832t
日期:2014.3.21
An unprecedented oxa- versus thia-selectivity has been observed in Prins cyclization of 6-mercaptohex-3-en-1-ol with aldehydes. In the presence of a stoichiometric amount of strong Lewis or Bronsted acids, the reaction provides the hexahydro-2H-thieno[3,2-c]pyran skeleton predominantly via oxonium-Prins cyclization. In contrast, a catalytic amount of weak Lewis or Bronsted acids provides the hexahydro-2H-thiopyrano[4,3-b]furan preferentially through thionium-Prins cyclization.