Development of an efficient method for synthesizing N-heterocyclic compounds based on a divalent titanium complex

A new titanium complex（徐D12 - 1-propene）Ti(O-i-Pr) D22 - D2 (1)，generated in situ by treatment of Ti(O-i-Pr) D24 D2 with 2equiv 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（徐D12 D1-alkyne）Ti（O-i-Pr）徐D22 D2，which be utilized as a vicinal vinylic dianion equivalent in the reactions with various kindselectrophiles. Allyl- and allenyltitaniums could readily be prepared from allylic or propargylicalcohol derivatives by the reaction with the through an oxidative addition pathway. While acetylenicesters resulted in an intramolecular nucleophilic acyl substitution (INAS) reaction to affordα,β-unsaturated carbonyl compounds，olefinic esters undergo tandem INAS and intramolecular carbonyl addition reactions to givecyclopropanols. Ene-ene, ene-yne，and yne-yne coupling reactions proceed in an intra- or intermolecular way via a cyclometallationreaction,and the generated titanacyclic complexes react with a variety of electrophiles in a chemo-, regio-，stereoselective way.By utilizing these reactions我们现在已经在synthesizing N-heterocycles and/or他们之前的研究，which include quinolones, pyrroles, indoles, optically active N-heterocycles2,6-disubstituted piperodines, β-lactams, azasugars and γ-amino carbonyl compounds。

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.