| Co-Investigator(Kenkyū-buntansha) |
OKAMOTO Sentaro Fac. of Biosci. and Biotech., Tokyo Institute of Technology, Assist. Professor, 生命理工学部, 助手 (00201989)
URABE Hirokazu Fac. of Biosci. and Biotech., Tokyo Institute of Technology, Assist. Professor, 生命理工学部, 助手 (10176745)
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| Research Abstract |
A new titanium complex (ηィイD12ィエD1-propene)Ti(O-i-Pr)ィイD22ィエD2 (1), generated in situ by treatment of Ti(O-i-Pr)ィイD24ィエD2 with 2 equiv of i-PrMgX (X = Cl or Br), nicely acts as a versatile titanium(II) equivalent to effect the following unique transformations. Thus, alkynes react with 1 to afford the alkyne-titanium complexes of type (ηィイD12ィエD1-alkyne)Ti(O-i-Pr)ィイD22ィエD2, which could be utilized as a vicinal vinylic dianion equivalent in the reactions with various kinds of electrophiles. Allyl- and allenyltitaniums could readily be prepared from allylic or propargylic alcohol derivatives by the reaction with 1 through an oxidative addition pathway. While acetylenic esters resulted in an intramolecular nucleophilic acyl substitution (INAS) reaction to afford α,β-unsaturated carbonyl compounds, olefinic esters undergo tandem INAS and intramolecular carbonyl addition reactions to give cyclopropanols. Ene-ene, ene-yne, and yne-yne coupling reactions proceed in an intra- or intermolecular way via a cyclometallation reaction, and the generated titanacyclic complexes react with a variety of electrophiles in a chemo-, regio-, stereoselective way.
By utilizing these reactions, we have now succeeded in synthesizing N-heterocycles and/or their precursors, which include quinolones, pyrroles, indoles, optically active N-heterocycles, 2,6-disubstituted piperodines, β-lactams, azasugars and γ-amino carbonyl compounds.
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