Uncatalyzed cationic olefin cyclizations of N-vinylic α-chloro-α-thioacetamides. Formation of β- and γ-lactams
摘要:
N-Vinylic alpha-chloro-alpha-thioacetamides were found to cyclize without a catalyst in two different manners depending upon the nature of the substituents at the terminus of the N-vinylic bond. Thus, bis(phenylthio)-substituted enamides 8a-c cyclized in a 4-exo-trig manner to give 4-methylene-beta-lactams 10a-c, whereas mono(phenylthio)-, monophenyl-, diphenyl-, and dialkyl-substituted congeners 23a,b, 28, and 38 cyclized in a 5-endo-trig manner to give gamma-lactams 26a,b, 30, and 39, respectively. The product 38 was transformed into an anticonvulsant agent ethosuximide (42).
N-Vinylic alpha-chloro-alpha-thioacetamides were found to cyclize without a catalyst in two different manners depending upon the nature of the substituents at the terminus of the N-vinylic bond. Thus, bis(phenylthio)-substituted enamides 8a-c cyclized in a 4-exo-trig manner to give 4-methylene-beta-lactams 10a-c, whereas mono(phenylthio)-, monophenyl-, diphenyl-, and dialkyl-substituted congeners 23a,b, 28, and 38 cyclized in a 5-endo-trig manner to give gamma-lactams 26a,b, 30, and 39, respectively. The product 38 was transformed into an anticonvulsant agent ethosuximide (42).