Synthesis of 2,4-disubstituted 3-chlorofurans and the effect of the chlorine substituent in furan Diels–Alder reactions
作者:Ram N. Ram、Neeraj Kumar
DOI:10.1016/j.tetlet.2007.11.193
日期:2008.1
3-chlorofurans were synthesized in 42–69% overall yields by CuCl/bpy-catalyzed halogen atom transfer radical cyclization of 1-substituted 2,2,2-trichloroethyl allyl ethers to 2-substituted 3,3-dichloro-4-(1-chloroalkyl)tetrahydrofurans followed by base promoted dehydrochlorination. Diels–Alder reactions of 4-substituted 2-(2-furyl)-, 2-styryl-, and 2-crotyl-3-chlorofurans with dimethyl acetylenedicarboxylate
2,4-二取代的3-氯呋喃通过CuCl / bpy催化的卤原子转移自由基环合反应合成了1-取代的2,2,2-三氯乙基烯丙基醚,生成2-取代的3,3-二氯,总产率为42-69% -4-(1-氯烷基)四氢呋喃,然后碱促进脱氯化氢。4-取代的2-(2-呋喃基)-,2-苯乙烯基-和2-巴豆基-3-氯呋喃与乙炔二羧酸二甲酯的狄尔斯-阿尔德反应仅发生在氯呋喃二烯部分上,而不发生在非氯化呋喃二烯或氯化环外二烯的替代品,证明了呋喃Diels-Alder反应中卤素效应的优势。