Wittig-type olefination catalyzed by PEG-telluride.
Soluble poly(ethylene glycol) (PEG)-supported telluride 2 was designed and synthesized for catalytic Wittig-type reactions. It was found that the catalytic loading could be reduced from 20 to 2 mol % by the introduction of PEG (even to 0.5 mol % when some telluride salts were used as the catalyst). Under the catalytic reaction conditions, a wide variety of aldehydes with different structures could react with bromoacetate to afford beta-substituted or alpha,beta-disubstituted unsaturated esters in high yields with excellent E-stereoselectivity. The modified process, by using sodium bisulfite instead of triphenyl phosphite, represented a very simple product isolation procedure. The roles of PEG for promoting the ylide formation and stabilizing the catalytic species were disclosed. The mechanism was also studied.
Huang
Zheng-Zheng
ZZ
State Key Laboratory of Organometallic Chemistry, Shanghai Institute of Organic Chemistry, 354 Fenglin Lu, Shanghai 200032, China.
Ye
Song
S
Xia
Wei
W
Yu
Yi-Hua
YH
Tang
Yong
Y