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Astonishing Alkylation and Unusual Reduction Reactions of Anionic Titanium( II ) Isopropoxide Complexes: Evidence for SET Processes in Transition‐Metal Oxidative Additions
Author(s) -
Eisch John J.,
Gitua John N.
Publication year - 2002
Publication title -
european journal of inorganic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.667
H-Index - 136
eISSN - 1099-0682
pISSN - 1434-1948
DOI - 10.1002/1099-0682(200212)2002:12<3091::aid-ejic3091>3.0.co;2-y
Subject(s) - chemistry , alkylation , lithium (medication) , ketone , butyllithium , titanium , isopropyl , benzene , steric effects , metalation , organic chemistry , medicinal chemistry , catalysis , medicine , endocrinology
Abstract A mixture of titanium( II ) isopropoxide and lithium isopropoxide (1:2), generated in THF by the treatment of titanium( IV ) isopropoxide with two equivalents of n ‐butyllithium, has been shown to be an unexpected alkylating agent as well as an unusual reducing agent for a wide variety of organic substrates. Since titanium( II ) isopropoxide, which is free of any lithium isopropoxide, neither causes alkylation of any of the same substrates nor is such a powerful reductant, it is proposed that the lithium isopropoxide activates titanium( II ) isopropoxide for such unusual reactions by the formation of the lithium salt coordination complex Li 2 Ti[O i Pr] 4 . Illustrative of the unprecedented alkylations are the transformations, after hydrolysis, of various substituted benzonitriles to isopropyl‐substituted phenyl ketones, of (dichloromethyl)benzene to, principally, 2‐methyl‐1‐phenyl‐1‐propene and of (trichloromethyl)benzene to isopropyl phenyl ketone. By comparing the reducing actions of Li 2 Ti[O i Pr] 4 and Ti[O i Pr] 2 individually, it has been shown that, generally, the lithium salt is the more powerful reductant for epoxides, benzylic halides and conjugated olefins. From the reactions of Li 2 Ti[O i Pr] 4 with the benzonitriles, styrene, the isomeric stilbene oxides and cis ‐stilbene, cogent evidence is marshaled for the operation of SET processes, sensitive to steric hindrance, in such alkylations and reductions. (© Wiley‐VCH Verlag GmbH, 69451 Weinheim, Germany, 2002)