Aminotroponiminate Zinc Complexes with Different Leaving Groups as Catalysts for the Intramolecular Hydroamination of Alkenes

The (aminotroponiminato)phenylzinc complexes {N-isopropyl-2-(isopropylamino)troponiminato}phenylzinc, [{ATI(iPr)(2)}-ZnPh], {N-isopropyl-2-(isopropylamino)-5-(phenylsulfanyl)-troponiminato}phenylzinc, [{PhS-ATI(iPr)(2)}ZnPh], {N-cyclohexyl-2-(cyclohexylamino)troponiminato)phenylzinc, [{ATI-(Cy)(2)}ZnPh] and the corresponding bis(trimethylsilyl)amido compounds [{ATI(iPr)(2)}ZnN(SiMe3)(2)}, [{PhS-ATI(iPr)(2))ZnN(SiMe3)(2)}, and [{ATI(Cy)(2)}ZnN(SiMe3)(2)] were prepared and fully characterized, These compounds were obtained by reaction of the corresponding ammotroponimines with ZnPh2 and [Zn{N(SiMe3)(2)}(2)], respectively. The new complexes were compared with the corresponding methylzinc complexes, which were previously reported, to study the influence of the substituents of the zinc atom in the catalytic hydroamination/cyclization reaction. In the presence of equimolar amounts of [PhNMe2H][B(C6F5)(4)] it was shown that the methyl und phenyl compounds show comparable activities, while those bearing a bis(trimethylsilyl)amido group are significantly slower. Obviously the size of the leaving group and the nature of the formed by-product have a significant influence on the reaction rate. ((C) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)