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Tuning the Reactivity of Oxygen/Sulfur by Acidity of the Catalyst in Prins Cyclization: Oxa- versus Thia-Selectivity
- Subba Reddy, B. V., Venkateswarlu, A., Borkar, Prashant, Yadav, J. S., Sridhar, B., Grée, René
- Journal of organic chemistry 2014 v.79 no.6 pp. 2716-2722
- acidity, aldehydes, catalysts, organic chemistry, oxygen, sulfur
- 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 Brønsted 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 Brønsted acids provides the hexahydro-2H-thiopyrano[4,3-b]furan preferentially through thionium-Prins cyclization.