title: Reaction of magnesium alkylidene carbenoids with lithium alpha-sulfonyl carbanions: a novel synthesis of tri- and tetra-substituted allenes from 1-chlorovinyl p-tolyl sulfoxides and sulfones.
abstract: Treatment of 1-chlorovinyl p-tolyl sulfoxides, which were synthesized from ketones and chloromethyl p-tolyl sulfoxide, with ethylmagnesium chloride or isopropylmagnesium chloride at below -78 degrees C gave magnesium alkylidene carbenoids in about 90% yields. The reaction of the generated carbenoids with lithium alpha-sulfonyl carbanions was found to afford tri- and tetra-substituted allenes. Both cyclic ketones and acyclic ketones were useful in this procedure. However, the 1-chlorovinyl p-tolyl sulfoxides derived from aldehydes gave only rearranged products, acetylenes, under the reaction conditions. The magnesium alkylidene carbenoid derived from an optically active 1-chlorovinyl p-tolyl sulfoxide was treated with lithium alpha-carbanion of 1-naphthyl phenyl sulfone; however, the obtained allene was found to be racemic. The mechanism of this reaction is also discussed.
authors.affiliation: Department of Chemistry, Faculty of Science, Tokyo University of Science, Kagurazaka, Shinjuku-ku, Tokyo 162-8601, Japan. tsatoh@ch.kagu.tus.ac.jp
authors.forename: Tsuyoshi
authors.initials: T
authors.lastname: Satoh
authors.forename: Tatsuya
authors.initials: T
authors.lastname: Sakamoto
authors.forename: Masanori
authors.initials: M
authors.lastname: Watanabe
authors.forename: Koji
authors.initials: K
authors.lastname: Takano
mesh_terms: D008094:Lithium / Q000737:chemistry*; D008274:Magnesium / Q000737:chemistry*; D013450:Sulfones / Q000138:chemical synthesis*; D013454:Sulfoxides / Q000138:chemical synthesis*
chemical_list: D013450:Sulfones; D013454:Sulfoxides; D008094:Lithium; D008274:Magnesium