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A New Class of Enantioselective Catalytic 2‐Pyrone Diels–Alder Cycloadditions
Author(s) -
Wu Wanqing,
Min Long,
Zhu Lizhi,
Lee ChiSing
Publication year - 2011
Publication title -
advanced synthesis and catalysis
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.541
H-Index - 155
eISSN - 1615-4169
pISSN - 1615-4150
DOI - 10.1002/adsc.201000927
Subject(s) - chemistry , enantioselective synthesis , synthon , catalysis , bifunctional , cycloaddition , steric effects , diels–alder reaction , organic chemistry , organocatalysis
A highly enantioselective catalytic Diels–Alder (DA) cycloaddition of 2 H ‐pyran‐2,5‐diones (synthon of 5‐hydroxy‐2‐pyrones) has been developed with a Cinchona ‐derived thiourea as the catalyst. The conditions were optimized by using 0.2 equiv. of the catalyst and 0.1 equiv. of formic acid in 2‐propanol at room temperature, which afforded the DA products in yields of up to 90% ( exo / endo =5.5:1, 98% ee ) with trans ‐β‐nitrostyrene derivatives as the dienophiles. The structure/activity relationships of the bifunctional catalyst and the effects of the steric, electronic and hydrogen‐bonding properties of the dienophiles have been studied.