Uncatalyzed [4 + 2] Cycloadditions of 3-Nitrocoumarins with Vinyl Ethers in Solventless Conditions. A New Entry to Chromene Derivatives
作者:David Amantini、Francesco Fringuelli、Ferdinando Pizzo
DOI:10.1021/jo0260185
日期:2002.10.1
(ethyl vinyl ether (8), 2,3-dihydrofuran (9), and 3,4-dihydro-2H-pyran (10)) were investigated in water, in neat conditions, and in organic solvents. The cycloadditions do not require the use of catalysts and are highly endo diastereoselective, and in water the cyclic nitronates 13, 18, and 23 are converted into chromene derivatives via hydrolysis, decarboxylation, and acetalation reactions. A one-pot
研究了3-硝基香豆素5与富电子的亲双烯体(乙基乙烯基醚(8),2,3-二氢呋喃(9)和3,4-二氢-2H-吡喃(10))的[4 + 2]环加成反应。在水,纯净条件和有机溶剂中。环加成不需要使用催化剂,并且对内非对映选择性高,并且在水中,环状硝酸酯13、18和23通过水解,脱羧和缩醛化反应转化为亚甲基苯衍生物。基于在纯净/水条件下的连续反应的一锅法程序可将3-硝基香豆素5用作合成色酚,四氢呋喃-和四氢吡喃并色酮的结构单元。首次研究了将1,2-恶嗪环的CO键作为缩醛的一部分的环状硝酸酯的水解。