TY - JOUR
T1 - Diels-Alder cycloadditions of 5-hydroxy-2-pyrones
T2 - 2H-pyran-2,5-diones and 5-(tert-butyldimethylsilyloxy)-2-pyrones as synthons
AU - Wu, Wanqing
AU - He, Shuzhong
AU - Zhou, Xiongfei
AU - Lee, Chi Sing
PY - 2010/2
Y1 - 2010/2
N2 - Diels-Alder (DA) cycloadditions of 5-hydroxy-2-pyrones based on the use of 2H-pyran-2,5-diones and 5-(tert-butyldimethylsilyloxy)-2-pyrones as synthons have been developed. Upon treatment either with a base or with a Lewis acid, 2Hpyran-2,5-diones equilibrated to 5-hydroxy-2-pyrones and underwent DA cycloaddition. The base-catalyzed protocol was optimized with cHex 2NMe (0.1 equiv.) in tBuOH at room temperature, which gave the tricyclic cycloadducts in yields of up to 81% (endo/exo = 6.2:1), The Lewis-acid-promoted protocol was optimized by conversion of 2H-pyran-2,5-diones into 5-(tert-butyldimethylsilyloxy)-2-pyrones and use of BF3· OEt2, which afforded the same DA products in yields of up to 90% (endo/exo = 12:1).
AB - Diels-Alder (DA) cycloadditions of 5-hydroxy-2-pyrones based on the use of 2H-pyran-2,5-diones and 5-(tert-butyldimethylsilyloxy)-2-pyrones as synthons have been developed. Upon treatment either with a base or with a Lewis acid, 2Hpyran-2,5-diones equilibrated to 5-hydroxy-2-pyrones and underwent DA cycloaddition. The base-catalyzed protocol was optimized with cHex 2NMe (0.1 equiv.) in tBuOH at room temperature, which gave the tricyclic cycloadducts in yields of up to 81% (endo/exo = 6.2:1), The Lewis-acid-promoted protocol was optimized by conversion of 2H-pyran-2,5-diones into 5-(tert-butyldimethylsilyloxy)-2-pyrones and use of BF3· OEt2, which afforded the same DA products in yields of up to 90% (endo/exo = 12:1).
KW - 2-Pyrones
KW - Cycloaddition
KW - Lactones
UR - https://www.scopus.com/pages/publications/76449114032
U2 - 10.1002/ejoc.200901040
DO - 10.1002/ejoc.200901040
M3 - Journal article
AN - SCOPUS:76449114032
SN - 1434-193X
SP - 1124
EP - 1133
JO - European Journal of Organic Chemistry
JF - European Journal of Organic Chemistry
IS - 6
ER -