Studies on Pd(II)-catalyzed synthesis of (Z)-alpha-haloalkylidene-beta-lactones from cyclocarbonylation of 2-alkynols and the subsequent coupling reactions.
[reaction: see text] A good regio- and stereoselectivity was observed for the PdCl2-catalyzed cyclocarbonylation of 2-alkynols with CuCl2 affording (Z)-alpha-chloroalkylidene-beta-lactones. The highly optically active (Z)-alpha-chloroalkylidene-beta-lactones could be easily prepared from the readily available optically active propargylic alcohols. The Pd(II)-catalyzed cyclocarbonylation of 2-alkynols with CuBr2 was also studied. Although the yields of (Z)-alpha-bromoalkylidene-beta-lactones were low, due to the relatively higher activity of the C-Br bond, the coupling reactions of (Z)-alpha-bromoalkylidene-beta-lactones were quite smooth to afford the corresponding products in high yields. A rationale for this reaction is discussed.
Ma
Shengming
S
State Key Laboratory of Organometallic Chemistry, Shanghai Institute of Organic Chemistry, Chinese Academy of Sciences, 354 Fenglin Lu, Shanghai 200032, P R China. masm@mail.sioc.ac.cn
Wu
Bin
B
Jiang
Xuefeng
X
Zhao
Shimin
S