Synthesis and structral characterization of an azatitanacyclobutene:: the key intermediate in the catalytic anti-Markovnikov addition of primary amines to α-alkynes

Reaction of the imidotitanium complexes [Ti((NBu)-Bu-t)(N2Npy)- (py)] (1) and [Ti(N-2,6-(C6H3Pr2)-Pr-i)(N2Npy)(py)] (2) with phenyl acetylene and tolyl acetylene in toluene gave the corresponding {2+2} cycloaddition products [Ti(N2Npy){kappa(2)-N(Bu-t)CH=CR)] (R = Ph: 3, Tol: 4) and [Ti(N2Npy){kappa(2)-N(2,6-(C6H3Pr2)-Pr-i)CH=CR)] (R = Ph: 5, Tol: 6). Complex 6 is the first example of a key intermediate in the anti-Markovnikov addition of a primary amine to a terminal acetylene which has been structurally characterized by X-ray diffraction.