Synthesis and structural characterization of an azatitanacyclobutene: the key intermediate in the catalytic anti-Markovnikov addition of primary amines to [small alpha]-alkynes

Reaction of the imidotitanium complexes Ti(N(t)Bu)(N(2)N(py))(py)](1) and Ti(N-2,6-C(6)H(3)(i)Pr(2))(N(2)N(py))(py)](2) with phenyl acetylene and tolyl acetylene in toluene gave the corresponding 2+2] cycloaddition products Ti(N(2)N(py))kappa(2)-N((t)Bu)CHdouble bond]CR]](R = Ph:3, Tol:4) and Ti(N(2)N(py))kappa(2)-N(2,6-C(6)H(3)(i)Pr(2))CHdouble bond]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.