Intramolecular hydroamination catalysis using trans-N,N′-dibenzylcyclam zirconium complexes

The syntheses of (Bn2Cyclam)Zr(NMe2)2 (1), (Bn2Cyclam)Zr(NH2,6-MePh)Cl (2) and (Bn2Cyclam)Zr(N2,6-MePh) (3) are described. The reactivity of 1, 3, (Bn2Cyclam)Zr(CH2Ph)2 (4) and ((C6H4CH2)2Cyclam)Zr (5) as hydroamination catalysts of aminoalkenes is reported. High conversions of the primary gem-disubstituted aminoalkenes in 5- or 6-member ring N-heterocycles were observed. Reactions of 1, 4 and 5 with CH2CHCH2CPh2CH2NH2 gave (Bn2Cyclam)Zr(NHR)2 (6) (R = CH2CPh2CH2CHCH2) that on heating converts sequentially into the mono-ortho-metallated species ((C6H4CH2)BnCyclam)Zr(NHR) (7) and the bis-ortho-metallated ((C6H4CH2)2Cyclam)Zr (5), simultaneously with the hydroamination product.

(Bn2Cyclam)Zr(NMe2)2 (1), (Bn2Cyclam)Zr(N2,6-MePh) (3), (Bn2Cyclam)Zr(CH2Ph)2 (4) and ((C6H4CH2)2Cyclam)Zr (5) are hydroamination catalysts of aminoalkenes. The NMR study of the reaction showed that (Bn2Cyclam)Zr(NHR)2 (6), the mono-ortho-metallated species ((C6H4CH2)BnCyclam)Zr(NHR) (7) and the bis-ortho-metallated ((C6H4CH2)2Cyclam)Zr (5) interconvert to each other upon addition of amine and/or pyrrolidine formation.Figure optionsDownload as PowerPoint slideResearch highlights
► Zirconium alkyl, amido and imido complexes were tested as hydroamination catalysts.
► First complexes supported by a cyclam-based ligand promoting hydroamination.
► Mechanistic studies of the hydroamination reactions are presented.