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

Abstract Reactions of the chiral alcohol rac 6,7-dihydro-5H-pyrrolo[1,2- a ]imidazol-7-ol [(R,S)-LH] with R 3 Al (R =  t Bu, Et) have been studied. An influence of reaction conditions on the product structures and distributions was found. The dimeric products (Al 2 R 4 L 2 ) [R =  t Bu ( 1 ), R = Et ( 2 )] were formed in the reactions of R 3 Al 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 C 4 N 2 O 2 Al 2 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.