W. R. Hertler, T. RajanBabu, D. W. Ovenall
Aug 1, 1988
Citations
0
Influential Citations
39
Citations
Journal
Journal of the American Chemical Society
Abstract
The polyunsaturated monomers, methyl pentadienoate (1). methyl and ethyl 2-methylpentadienoate (2 and 3), ethyl sorbate (4), ethyl muconate (S), and 3-(2,4-hexadien- l-ylidene)-4,5-dihydrofurone (6) undergo group transfer polymerization (GTP). The reaction can be initiated by silyl ketene acetals or the silyl polyenolates 10-15 as well as the allylic silane 16 in the presence of a variety of nucleophilic anion catalysts. When silyl ketene acetals are used to initiate GTP of 1-3, 5, and 6, control of AT,, is difficult, and polymers with I@" much higher than theory are obtained. an closer to theory and low polydispersity are achieved by initiation with silyl polyenolates. Regiospecific 1,4-polymerization occurs with the diene monomers, and 1,6-polymerization occurs with the triene lactone 6. GTP of ethyl sorbate and ethyl muconate proceeds with 2:l erythro and 2.1 meso selectivity and 3.1 trans-cis geometry of the backbone double bond. The triene lactone 6 appears to show no diastereoselectivity but high trans selectivity with respect to double-bond geometry. The unsubstituted silyl dienolates 10 and 12 and the silyl trienolate 14 show regiospecific initiation of GTP of MMA at the 2-position. The 2-methyl diene homologues 11 and 13 show regioselective initiation of GTP of MMA at the 2-position, with about 28% initiation at the 4-position.