Acid-promoted Prins cyclizations of enol ethers to form tetrahydropyrans.
Trifluoroacetic acid efficiently catalyzes Prins cyclizations of enol ethers 8 to provide tetrahydropyrans 9 and 10. These tetrahydropyrans are isolated with combined yields of 42-85% and stereoselectivities at C(4) ranging from 95:5 to 50:50 depending on the nature of the substituent R. Unique byproducts of these cyclizations that reveal the presence of underlying equilibria have been isolated and identified. [reaction: see text]
Hart
David J
DJ
Department of Chemistry, The Ohio State University, 100 West 18th Avenue, Columbus, OH 43210, USA. hart@chemistry.ohio-state.edu
Bennett
Chad E
CE
D002384:Catalysis; D003500:Cyclization; D004987:Ethers / Q000737:chemistry*; D011714:Pyrans / Q000138:chemical synthesis*; D013237:Stereoisomerism; D014269:Trifluoroacetic Acid / Q000737:chemistry*
D004987:Ethers; D011714:Pyrans; D014269:Trifluoroacetic Acid