| Research Abstract |
We have developed efficient inter-and intramolecular cyclization reactions of unsaturated compounds mediated by a divalent titanium reagent. Based on these reactions, in this project we developed Ti(II)-mediated tandem or domino inter-and intramolecular coupling reactions of unsaturated compounds which enable multiple bond-forming in one-pot.
Thus, 1,4-diynes reacted with the Ti(II)-reagent and allylic compounds to provide allyltitanated intermediate and this was further reacted with one more equivalent of the Ti(II)-reagentin situto provide cyclic bistitanated organic molecule in good yield, which was reacted with a various kind of electrophiles such as H+, D+, I+ and aldehydes to afford the corresponding hydrolysis, deuteriolysis, iodolysis and carbonyl addition compounds. The reactions involved maximum five-bond forming in a single vessel.
Extensively, the method was applied to intra-/intramolecular domino reactions such as bicyclization of functionalized 2,7-enynes to bicyclo[3.3.0]-, [4.3.0]-carbo-and heterocyclic compounds.
Considering efficiency, economical advantage and/or high stereoselectivity of the reactions developed here and also non-toxity and inexpensiveness of the Ti(II)-reagent, we believe that the methods might be useful as a powerful tool in organic synthesis.
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