A series of symmetrical and unsymmetrical N,N'-disubstituted aminotroponimines (ATIHs) have been prepared. Substituents ranging from linear to cyclic alkyl groups, chelating ethers, and aryl groups were employed. The corresponding aminotroponiminate zinc complexes were then synthesized and characterized by a number of techniques, including by X-ray crystallography. Herein we report on the investigations into their activity in the intramolecular hydroamination of nonactivated alkenes. We also demonstrate that complexes bearing ligands with cyclic alkyl groups show superior activity in a number of selected reactions with functionalized aminoalkenes.

The new zinc compound N-cyclohexyl-2-(cyclohexylamino)troponiminate zinc methyl, [(Cy)2ATI]ZnMe, was synthesized and showed a superior reactivity in the intramolecular hydroamination reaction of non-activated alkenes compared to previously reported homogeneous zinc complexes.

The electronically modified zinc complex 5-phenylsulfanyl-N-isopropyl-2-(isopropylamino)troponiminate zinc methyl, [(PhS-ATI(iPr)2)ZnMe], was synthesized. It showed an increased reactivity in the intramolecular hydroamination reaction of non-activated alkenes compared to a previously-reported, non-substituted complex.

Diethylzinc and dimethylanilinium tetrakis(pentafluorophenyl)borate were found to catalyze hydroaminations at room temperature in high efficiency and very short reaction times. The reactivity of the proposed cationic zinc species, which is assumed to catalyze the reaction, strongly depends on the coordinative abilities of the counterion.

Substituted aminotroponimines, {R-ATI(iPr)2}H (R = Br, I, PhN2, NO2, PhS, PhSe, PhTe, 3,5-(CF3)2C6H3S, PhS(O)), bearing different functional groups in the 5-position were prepared. Reaction of these compounds with ZnMe2 in toluene at 0 °C delivered the corresponding methyl zinc complexes [{R-ATI(iPr)2}ZnMe] in high yields. The solid state structures of four selected examples were established via single-crystal X-ray diffraction analysis. In all compounds the zinc atoms are coordinated in a trigonal-planar fashion. All complexes were investigated as catalysts in the intramolecular hydroamination of non-activated alkenes. The attachment of electron-withdrawing groups in the 5-position such as nitro-or sulfoxide decreased the activity of the corresponding zinc catalysts. In contrast, donor substituents such as a thioether moiety at the backbone of the ligand increased the stability of the chelate and also rendered the zinc atom more reactive. On the other hand, the 5-brominated compound is very labile under the catalytic conditions used. In order to study the potential of an additional beneficial effect from the steric environment around the zinc atom on both reactivity and stability of the corresponding complexes, a prototypic ligand bearing a 5-phenylsulfanyl substituent at the backbone and two cyclohexyl substituents at the nitrogen atoms, {PhS-ATI(Cy)2}H, and its corresponding zinc complex, [{PhS-ATI(Cy)2}ZnMe], were synthesized.