REACTIONS OF ALPHA, BETA- ACETYLENIC SULFONES, ALPHA, BETA- ACETYLENIC SULFIDES AND ALPHA, BETA- VINYLIC SULFONES WITH ORGANOLITHIUM AND GRIGNARD REAGENTS
Abstract
The reactions of (alpha),(beta)-acetylenic sulfones with organolithium and Grignard reagents in THF were investigated. Displacement occurs in which a higher acetylene and a sulfinate salt are produced. The reaction with organolithiums is rapid, taking less than ten seconds in at least one case even at low temperatures, while the reaction with Grignard reagents takes several hours at room temperature to ensure maximum yields. There are two requirements for the reaction to proceed favorably: (1) The potential sulfinate leaving group must not possess a labile hydrogen (e.g., (alpha)-sulfonyl hydrogen); (2)The acetylenic portion must not possess a (gamma) (propargylic) hydrogen. Both requirements stem from the fact that metalation of relatively acidic positions competes favorably with the net substitution process. Mechanistic aspects of the reactions are discussed. Evidence is given for delivery of the organometallic to the (alpha)-carbon, assisted in intramolecular fashion by the sulfonyl oxygens. Reactions of (alpha),(beta)-acetylenic sulfides with organolithium reagents in THF and hexane-THF were examined. A preponderance of nucleophilic attack on sulfur was observed, except with phenylethynyl sulfides, using the mixed solvent hexane-THF (89:11), which gave almost exclusive attack on the acetylenic (alpha)-carbon to displace thiolate. The reactions of phenyl-substituted (alpha),(beta)-vinylic sulfones with n-butyllithium were also investigated. It was found that (beta)-phenyl vinylic sulfones react with n-butyllithium in THF to metalate either the (alpha) or (beta) vinylic carbon, or in the absence of (alpha) or (beta) vinylic hydrogens, by substitution of the sulfonyl moiety. The preparation of some norbornadienyl vinylic sulfones using (alpha),(beta)-acetylenic sulfones as dienophiles in Diels-Alder reactions is also described.
Degree
Ph.D.
Subject Area
Organic chemistry
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