Intramolecular cyclization reactions of carbonyl derivatives of hydroxysulfones

The γ and δ-hydroxysulfone tert-butyl ester derivatives are easily prepared from the corresponding hydroxysulfones by phase-transfer alkylation reactions. The sulfonyl carbanions of are readily generated upon treatment with LHMDS in THF at −78°C and undergo intramolecular acylation reactions to give a variety of functionalized cyclic ethers in good yields. The intramolecular aldol-type reaction of the sulfonyl carbanion of is useful for the preparation of six-membered oxacyclic ring systems with high diastereo selective control and is best carried out under equilibrating conditions (tBuOK in toluene). This study clearly shows that it is possible to generate an α-sulfonyl carbanion and effect its intramolecular cyclization even in the presence of other protons of comparable acidity elsewhere in the substrate. The scope, limitations and synthetic utility of this intramolecular cyclization strategy have been examined.