The first early transition metal-catalyzed enyne cyclization reaction is described. The system converts enyne substrates to bicyclic iminocyclopentenes through the use of 10 mol % of Cp(2)Ti(PMe(3))(2) in the presence of a silyl cyanide. Subsequent hydrolysis produces the corresponding bicyclic cyclopentenones in good overall yield. The cyclization reaction is tolerant of polar functional groups such as ethers, amines, and esters and is diastereoselective with certain chiral enyne substrates.
“Development of a Titanocene-Catalyzed Enyne Cyclization/Isocyanide Insertion Reaction”, J. Am. Chem. Soc., 1994, 116(19), 8593-8601.