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Titanacyclobutenes or Titanium Vinyl Carbene Complexes? Reactivity of Organotitanium Species Generated by the Reaction of γ‐Chloroallyl Sulfides with a Titanocene(II) Reagent
Author(s) -
Shono Tomohiro,
Kurashige Rie,
Mukaiyama Ryo,
Tsubouchi Akira,
Takeda Takeshi
Publication year - 2007
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.200601418
Subject(s) - reactivity (psychology) , carbene , chemistry , styrene , reagent , titanium , organic chemistry , polymer chemistry , conjugated system , medicinal chemistry , catalysis , polymer , copolymer , medicine , alternative medicine , pathology
The reactivity of the organotitanium species generated by the reductive titanation of γ‐chloroallyl sulfides with the titanocene(II) reagent [Cp 2 Ti{P(OEt) 3 } 2 ] was studied. The organotitanium species formed from α‐monosubstituted γ‐chloroallyl sulfides reacted with 1,5‐diphenylpentan‐3‐one and styrene to produce conjugated dienes and vinyl cyclopropanes as major products, thus suggesting the formation of vinyl carbene complexes as intermediates. On the contrary, the organotitanium species generated from acyclic β,γ‐disubstituted γ‐chloroallyl sulfides revealed titanacyclobutene‐like reactivity, and their reaction with 1,5‐diphenylpentan‐3‐one produced homoallyl alcohols. These organotitanium species did not react with styrene, but did react with dichlorophenylphosphine to afford phosphacyclobutenes. In the case of β‐monosubstituted, γ‐monosubstituted, and α,γ‐disubstituted γ‐chloroallyl sulfides, the organotitanium species reacted with both 1,5‐diphenylpentan‐3‐one and styrene. The former reaction produced homoallyl alcohols and the latter gave vinyl cyclopropanes or unconjugated dienes. These results suggest that titanacyclobutenes and/or titanium vinyl carbene complexes are produced by the reductive titanation of γ‐chloroallyl sulfides depending on their substitution patterns.