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.
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.
Satoh
Tsuyoshi
T
Department of Chemistry, Faculty of Science, Tokyo University of Science, Kagurazaka, Shinjuku-ku, Tokyo 162-8601, Japan. tsatoh@ch.kagu.tus.ac.jp
Sakamoto
Tatsuya
T
Watanabe
Masanori
M
Takano
Koji
K
D008094:Lithium / Q000737:chemistry*; D008274:Magnesium / Q000737:chemistry*; D013450:Sulfones / Q000138:chemical synthesis*; D013454:Sulfoxides / Q000138:chemical synthesis*
D013450:Sulfones; D013454:Sulfoxides; D008094:Lithium; D008274:Magnesium