Asymmetric Reactions During the Polymerization of (RS)-Propylene Sulfide by n-Butyllithium-Lithium (-)-Menthoxide

Abstract

Studies of the polymerization of racemic propylene sulfide (PS) by n-BuLi-(-)LiOR* (* denotes chiral group) show that the development of optical activity in the polymers can arise both by the ordinary asymmetric selective polymerization of (S)-PS and by two secondary reactions: first, by selective desulfurization of (R)-PS (both the unreacted PS and the polymer have a negative rotation at small conversions of PS into polymer); and second, by selective decomposition of (S) polymer chains. The latter is also confirmed by the asymmetric decomposition of optically inactive poly(propylene sulfides) by the same catalytic system. Possible reaction mechanisms for these processes are considered.

Recent advances in enantioselective ring-opening polymerization and copolymerization

“…Thiirane. Early work on enantioselective ROP of methylthiirane showed low enantioselectivities [172][173][174][175] . In 1981, Spassky and coworkers found the chiral initiator of ZnEt 2 /(S)-BINOL could selectively polymerize (S)-methylthiirane from the racemic mixture (Fig.…”

Recent advances in the ring-opening polymerization of sulfur-containing monomers

“…86 Other nucleophiles were examined, however most of these resulted in the formation of oligomers in poor yield due to a slow initiation rate coupled with poor solubility in the reaction media. 26,87–89…”

Asymmetric Polymerization

“…The catalyst was active and selective for 1 -butene oxide, 1 -hexene oxide, and styrene oxide ( k rel = 63 -330). Propylene sulfi de was polymerized enantiomer -selectively in the presence of optically active zinc [446 -449] , lithium [450] , or cadmium [451,452,455] catalysts. The ratio of consumption rate of ( S ) -monomer to that of ( R ) -monomer, k S / k R , reached up to 20 in the polymerization using Et 2 Zn/ 40 system [448,449] .…”