274690-29-8Relevant articles and documents
Photochemistry of N-heterocycles. 7: Light induced reductive ring contractions of sixmembered cyclic iminium ions
Nagy, Jozsef,Madarasz, Zoltan,Rapp, Rudolf,Szoelloesy, Aron,Nyitrai, Jozsef,Doepp, Dietrich
, p. 281 - 290 (2007/10/03)
Photochemically induced reductive ring contractions, previously observed for 2,5-dihydro-1,2,4-triazines, have also been verified for 1,4-dihydropyrimidines 2a,b, the dihydro-1,2,4,5-tetrazine 9, and dihydro-1,3,5-triazines 11a,b giving rise to fivemembered fully unsaturated heterocycles (pyrroles 4a,b, imidazoles 13a,b, and triazole 10, respectively). The 1,4-dihydropyrazines 15a-j tend to decompose in acidified 2-propanol in the dark, but on irradiation they also undergo reductive ring contraction furnishing solely the 1,2,5-triarylpyrroles 16a-d rather than the (a priori also possible) isomeric 1,3,4-triarylpyrroles 17a-d. In contrast, the 3,6-diphenylpyrid-azine 18 gives the 4-isopropyl-analogue 19 in low yield upon irradiation in hydrogen chloride saturated 2-propanol. Wiley-VCH Verlag GmbH, 2000.