Diastereoselectivity-switchable and highly enantioselective 1,3-dipolar cycloaddition of nitrones to alkylidene malonates.
Trisoxazoline 1/Co(ClO(4))(2).6H(2)O catalyzed the 1,3-cycloaddition between nitrones 3 with alkylidene malonates 2 at 0 degrees C to give the isoxazolidines with both high enantioselectivity and high exo selectivity. However, when the temperature was lowered from 0 to -40 degrees C, the same cycloaddition afforded endo isomers as the major products with good to high enantioselectivity. A mechanism is provided.
Huang
Zheng-Zheng
ZZ
State Key Laboratory of Organometallic Chemistry, Shanghai Institute of Organic Chemistry, Chinese Academy of Science, 200032 Shanghai, China.
Kang
Yan-Biao
YB
Zhou
Jian
J
Ye
Meng-Chun
MC
Tang
Yong
Y