Addition of twisted 1,1-bis(thioacyl)-2,2-diaminoethylenes to dimethyl acetylenedicarboxylate. 2. Structure determination of two isomeric spiro adducts by x-ray crystallography and of a rearrangement product by the 2D INADEQUATE technique
摘要:
1,3-Dialkyl-2-(4,4-dimethyl-2,6-dithioxocyclohexylidene)imidazolidines (twisted push-pull ethylenes) react smoothly with dimethyl acetylenedicarboxylate (DMAD) but require at least 3 equiv of DMAD for complete consumption. Chromatography of the complex reaction mixture gave two isomeric 1:2 adducts, shown by X-ray crystallography to be (E)- and (Z)-[1,2-bis(methoxycarbonyl)vinyl]thio-susbstituted thiopyran-4-spiro-2'-imidazolidines. Treatment of the spior compounds with dilute nonaqueous acid led to isomers in which the imidazolidine ring had opened, and acid hydrolysis gave a thiopyrone and its enol tautomer. Continued chromatography of the original reaction mixture gave three new compounds, a thiopyran-4-thione, a tetrakis-(methoxycarbonyl)-1,4-dithiaphenalene, and a precursor to this with the same ring system. The formation of these compounds requires migration of a sulfur atom from the cyclohexene ring to the annelated thiopyran ring, and a possible mechanism is discussed. The dithiaphenalene structure was firmly established by the 2D INADEQUATE technique.
Addition of twisted 1,1-bis(thioacyl)-2,2-diaminoethylenes to dimethyl acetylenedicarboxylate. 2. Structure determination of two isomeric spiro adducts by x-ray crystallography and of a rearrangement product by the 2D INADEQUATE technique
作者:Agha Zul Qarnain Khan、Jan Sandstroem、Karl Eric Bergquist、Chih Yi Cheng、Sue Lein Wang
DOI:10.1021/jo00016a021
日期:1991.8
1,3-Dialkyl-2-(4,4-dimethyl-2,6-dithioxocyclohexylidene)imidazolidines (twisted push-pull ethylenes) react smoothly with dimethyl acetylenedicarboxylate (DMAD) but require at least 3 equiv of DMAD for complete consumption. Chromatography of the complex reaction mixture gave two isomeric 1:2 adducts, shown by X-ray crystallography to be (E)- and (Z)-[1,2-bis(methoxycarbonyl)vinyl]thio-susbstituted thiopyran-4-spiro-2'-imidazolidines. Treatment of the spior compounds with dilute nonaqueous acid led to isomers in which the imidazolidine ring had opened, and acid hydrolysis gave a thiopyrone and its enol tautomer. Continued chromatography of the original reaction mixture gave three new compounds, a thiopyran-4-thione, a tetrakis-(methoxycarbonyl)-1,4-dithiaphenalene, and a precursor to this with the same ring system. The formation of these compounds requires migration of a sulfur atom from the cyclohexene ring to the annelated thiopyran ring, and a possible mechanism is discussed. The dithiaphenalene structure was firmly established by the 2D INADEQUATE technique.