Synthesis of substituted aromatic compounds by Diels–Alder reactions of alkoxycyclobutenes produced via photocycloadditions between vinyl ethers and 1,3-dione enol esters
作者:Andrew J. Barker、Michael J. Begley、Alan M. Birch、Gerald Pattenden
DOI:10.1039/p19830001919
日期:——
The adduct (5) obtained from [2 + 2] photocycloaddition of ethyl vinyl ether to the 1,3-dione enol acetate (4) rapidly loses acetic acid producing the ethoxycyclobutene (7). On being warmed in the presence of a dienophile, the ethoxycyclobutene (7) undergoes electrocyclic ring-opening to give the ethoxydienone (8) followed by [4 + 2] cycloaddition to produce Diels–Alder adducts [e.g.(10) with dimethyl
从乙基乙烯基醚的[2 + 2]光环加成到1,3-二酮烯醇乙酸酯(4)中获得的加合物(5)迅速失去乙酸,生成乙氧基环丁烯(7)。在亲二烯体存在下加热后,乙氧基环丁烯(7)经历电环开环反应生成乙氧基二烯酮(8),然后进行[4 + 2]环加成反应生成狄尔斯-阿尔德加合物[例如(10)与乙酰化二羧酸二甲酯] ; 从(10)中除去乙醇,得到邻苯二甲酸二甲酯(11)。在“一锅法”反应中,将(5)与1,4-萘醌在含二甲苯的氧化铝中的溶液加热可得到取代的蒽醌(12),产率为95%。