Dioxopyrrolines. XLIX. Synthesis of azatropolones via photocycloaddition of 5-aryl-4-ethoxycarbonyl-1H-pyrrole-2,3-diones to acetylenes and ethylenes.
作者:Takehiro SANO、Yoshie HORIGUCHI、Yoshisuke TSUDA
DOI:10.1248/cpb.38.3283
日期:——
The first synthesis of derivatives of azatropolone, a new nitrogen heterocycle, and some of their chemical properties are described. Two routes to the azatropolone skeletone were developed; one is the photocycloaddition of dioxopyrrolines 1 to acetylenes followed by thermolysis or photolysis of the resulting cyclobutenes 2 to give the azatropolones 7 or 8, and the other is the ring expansion reaction of the cyclobutanes 5 obtained by the photocycloaddition of 1 to olefins followed by 2, 3-dichloro-5, 6-dicyano-1, 4-benzoquinone dehydrogenation of the resulting dihydroazepines 16 to give the azatropolones 7.The azatropolone rapidly consumed diazomethane; thus 7 gave the 3-O-methylazatropolones 18, while 8 gave mixtures of 3-O-methyl-19 and 2-O-methylazatropolones 20. The position of methylation was proved by the unambiguous synthesis of 18 and of 2-O-ethyl derivatives 24 from 16. The azatropolones 7 and 8, when treated with a protonic solvent, readily underwent a ring contraction reaction giving rise to the pyridine-2-carboxylates 29 and 30, respectively, thus demonstrating that the azatropolone nucleus has a strongly electrophilic character.
首次合成了氮杂环丙烷酮衍生物,并描述了它们的一些化学性质。开发了两条合成氮杂环丙烷酮骨架的途径;一种是将1,4-二氧杂环戊烯与乙炔进行光环加成,然后通过热解或光解得到的环丁烯2生成氮杂环丙烷酮7或8,另一种是通过环扩张反应将1,4-二氧杂环戊烯与烯烃光环加成得到的环丁烷5,然后通过2,3-二氯-5,6-二氰基-1,4-苯醌对得到的二氢氮杂卓16进行脱氢得到氮杂环丙烷酮7。氮杂环丙烷酮迅速消耗重氮甲烷;因此7得到了3-O-甲基氮杂环丙烷酮18,而8得到了3-O-甲基19和2-O-甲基氮杂环丙烷酮20的混合物。甲基化位置通过明确合成18和从16得到的2-O-乙基衍生物24得到了证明。当用质子溶剂处理时,氮杂环丙烷酮7和8容易发生环缩合反应,分别生成吡啶-2-羧酸酯29和30,这表明氮杂环丙烷酮核具有强亲电性。