Coupling Reaction of Magnesium Alkylidene Carbenoids with α-Sulfonylallyllithiums: An Efficient Route to Multi-Substituted Vinylallenes. -The method allows a ready access to various highly unsaturated title compounds. -(KIMURA, T.; KOBAYASHI, G.; ISHIGAKI, M.; INUMURA, M.; SAKURADA, J.; SATOH*, T.; Synthesis 2012, 23, 3623-3632, http://dx.doi.org/10.1055/s-0032-1317507 ; Dep. Chem., Fac. Sci., Sci. Univ. Tokyo, Shinjuku, Tokyo 162, Japan; Eng.) -Mais 13-035

A variety of 2‐monosubstituted and 2,2‐disubstituted 1‐chlorovinyl p‐tolyl sulfoxides was synthesized through a one‐pot procedure by the Horner‐Wadsworth‐Emmons reaction of carbonyl compounds with [chloro(diethoxyphosphoryl)(p‐tolylsulfinyl)methyl]lithium, which was generated from diethyl chlorophosphate, chloromethyl p‐tolyl sulfoxide, and lithium diisopropylamide in advance. The in situ‐prepared sulfoxides were directly converted into alkynes via the sulfoxide/magnesium exchange reaction with i‐PrMgCl and the subsequent Fritsch‐Buttenberg‐Wiechell rearrangement of the resulting magnesium alkylidene carbenoids.

A variety of vinylallenes were successfully synthesized from 1-chlorovinyl p-tolyl sulfoxides and allyl or vinyl sulfones. Allyl and vinyl sulfones served as α-sulfonylallyllithium sources were prepared from carbonyl compounds in three or four steps in good overall yields. The coupling reaction of α-sulfonylallyllithiums with magnesium alkylidene carbenoids, which were generated from 1-chlorovinyl p-tolyl sulfoxides and isopropylmagnesium chloride, afforded multi-substituted vinylallenes in up to 88% yield.

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