Photocycloaddition of 2,3-Dihydro-2,2-dimethyl-4<i>H</i>-thiopyran-4-one (a 4-Thiacyclohex-2-enone) to <i>bona fide</i> Triplet Quenchers. A Contradiction?
作者:Paul Margaretha、Kerstin Schmidt、Jürgen Kopf、Volker Sinnwell
DOI:10.1055/s-2007-965998
日期:2007.5
2,3-Dihydro-2,2-dimethyl-4H-thiopyran-4-one undergoes regiospecific photocycloaddition to 2-chloroacrylonitrile as well as regio- and stereospecific photocycloaddition to ethylidenemalononitrile. On irradiation in the presence of either 2,3-dimethylbuta-1,3-diene or isoprene, the same enone affords mainly [2+2]-cycloadducts and only minor amounts of (stepwise) [2+4]-cycloadducts, whereas quantitative quenching is observed in the presence of 2,5-dimethylhexa-2,4-diene. In contrast, the corresponding pyran is almost quantitatively quenched in the presence of any of the enenitriles or dienes mentioned.
2,3-二氢-2,2-二甲基-4H-噻喃-4-酮与 2-氯丙烯腈发生区域特异性光环加成反应,与亚乙基丙二腈发生区域和立体特异性光环加成反应。在 2,3-二甲基丁-1,3-二烯或异戊二烯存在下进行辐照时,同一烯酮主要产生 [2+2]- 环加成产物,仅产生少量(逐步的)[2+4]- 环加成产物,而在 2,5-二甲基己-2,4-二烯存在下则观察到定量淬灭。相反,相应的吡喃在上述任何一种烯腈或二烯的存在下都几乎定量淬灭。