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Stereoselective synthesis of tetrahydrofurans and tetrahydropyrans by acid-catalyzed cyclization of hydroxy selenides and hydroxy sulfides

โœ Scribed by Michelangelo Gruttadauria; Paolo Lo Meo; Renato Noto

Publisher
Elsevier Science
Year
1999
Tongue
French
Weight
846 KB
Volume
55
Category
Article
ISSN
0040-4020

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โœฆ Synopsis

The behaviour in acid media of hydroxy selenides and hydroxy sulfides (la-c and l'a-c) was investigated. The protection of the primary hydroxyl group in compounds la and l'a allowed the stereoselective synthesis of a substituted tetrahydrofuran ring, whereas compounds lb-c and l'b-c gave an efficient regiochemical control affording substituted tetrahydropyran rings. Tetrahydropyrans containing the phenylselanyl moiety were found to be in equilibrium in the cyclization reaction conditions, whereas tetrahydropyrans containing the phenylsulfanyl moiety were not. A mechanism for the above equilibration is proposed. Semiempirical (AM1, PM3) and ab initio (HF/3-21G*) calculations were used in an attempt to rationalize the experimental results.

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