Chiral dialkylaluminum 6,7-dihydro-5H-pyrrolo[1,2- a ]imidazol-7-olates: Synthesis, characterization and polymerization activity

Reactions of the chiral alcohol rac 6,7-dihydro-5H-pyrrolo[1,2-a] imidazol-7-ol [(R,S)-LH] with R3Al (R - Bu-t, Et) have been studied. An influence of reaction conditions on the product structures and distributions was found. The dimeric products (Al2R4L2) [R = Bu-t (1), R = Et (2)] were formed in the reactions of R3Al with one equivalent of (R, S)-LH as mixtures of the heterochiral (R, S) and homochiral (R, R) and (S, S) diastereomers. The X-ray diffraction measurements of the (R, S)- 1 and (R, S)-2 showed dinuclear complexes with bridging ON ligands and 10-membered C4N2O2Al2 central cycles. The molecules contain two chiral ligands demonstrating (R) and (S) configurations of CO carbon atoms. Polymerization tests showed that the complexes 1 and 2 have activity in the ROP of e-caprolactone. Kinetic studies revealed first order reaction of polymerization. (C) 2017 Elsevier B.V. All rights reserved.