STEREOCHEMISTRY OF RING-OPENING REACTIONS OF EPOXIDE WITH ALUMINUM AND ZINC PORPHYRINS - RELATION TO THE MECHANISM OF RING-OPENING POLYMERIZATION

Ring-opening reactions of 2,3-epoxybutanes with aluminum 5,10,15,20-tetraphenylporphine ((TPP)AlX (1; X = SPr, OMe)) and zinc 5,10,15,20-tetraphenyl-21-methylporphine ((NMTPP)ZnX (2; X = SPr, OMe)) were carried out in the presence of protic compounds such as 1-propanethiol (PrSH) and methanol (MeOH), where the cis- and trans-epoxides were converted to threo- and erythro-3-substituted 2-butanols, respectively. When the polymers of cis- and trans-2,3-epoxybutanes, prepared by the polymerizations with (TPP)AlCl, were cleaved with pentylsodium, dl- and meso-butanediols were obtained, respectively, as the diol fragments. Thus, the ring-opening reactions of 2,3-epoxybutanes with 1 and 2 both proceed with inversion of the configuration at the carbon atom of the epoxide ring where cleaved.