Reaktionen mit cyclischen Oxalylverbindungen, 26. Mitt. Cyclokondensation von 4,5-substituierten Thiophen- bzw. N-Alkylpyrrol-2,3-dionen mito-Phenylendiamin
Regio- and stereoselective photocycloadditions of heterocyclic 2,3-diones — Evidence for an unexpected 1,2-aroyl migration
摘要:
Photocyclization of the heterocyclic 2,3-diones 1a-d with electron rich alkenes affords regio- and stereoselectively the 2+2 adducts 2, from Ib with benzophenone as photosensitizer also the Paterno-Buchi adduct 3 is obtained. Similarly, with phenylethyne the cycloadducts 4 are formed in moderate to low yields, in case of Ic the azepinone 6 is the only reaction product. Thermolysis of 4a generates the pyrono compound 5. Irradiation of the N-arylpyrrolediones le, f and ethylvinyl ether give furo[3,2-c]pyrrolones 7 thus making evident an unexpected 1,2-benzoyl migration. Structural elucidation of all ring systems described is based upon X-ray analyses of 2d, 5 and 7f, respectively. (C) 1999 Elsevier Science Ltd. All rights reserved.
作者:Ewald Terpetschnig、Gerhard Penn、Gert Kollenz、Karl Peters、Eva-Maria Peters、Hans Georg von Schnering
DOI:10.1016/s0040-4020(01)96034-x
日期:1991.5
The heterocyclic 2,3-diones 1 – 3 have been found to undergo photochemical and thermal2+2-cycloaddition reactions via their 3-carbonyl group to diphenylketene and the diphenylketen-N-(4-methylphenyl)-imine. These reactions afford rearranged cycloadducts as well as 2+2-cycloreversion products.