title: Highly selective synthesis of bicyclic quinolizidine alkaloids and their analogues via double RCM reaction of N-alkynyl-N-(1,omega)-alkadienyl acrylamides.
abstract: The double ring-closing metathesis reaction of N-alkynyl-N-(1,omega)-alkadienyl acrylamides 1 using first- or second-generation Grubbs' catalyst afforded, in a highly selectively manner, the fused bicyclic quinolizidine alkaloid derivatives and their analogues bearing a 1,3-diene moiety, which may further undergo a Diels-Alder reaction with a dienophile to afford N-containing polycyclic compounds. The excellent selectivity of fused/dumbbell-mode cyclization has been realized by the higher reactivity of the electron-rich C=C bond or carbon-carbon triple bond combined with the lower reactivity of the electron-deficient C=C bond toward metallocarbenes and the thermodynamically more stable nature of fused bicyclic compounds 3 vs dumbbell-type bicyclic compounds 4.
authors.affiliation: State Key Laboratory of Organometallic Chemistry, Shanghai Institute of Organic Chemistry, Chinese Academy of Sciences, 354 Fenglin Lu, Shanghai 200032, PR China. masm@mail.sioc.ac.cn
authors.forename: Shengming
authors.initials: S
authors.lastname: Ma
authors.forename: Bukuo
authors.initials: B
authors.lastname: Ni
authors.forename: Zhiqiang
authors.initials: Z
authors.lastname: Liang