138835-97-9Relevant articles and documents
Triplet states mediating hydrogen abstraction in 4-acylpyrimidines, 2-acylpyridines, 2-acylpyrazines, and 3-acylpyridazines
Prathapan, Sreedharan,Robinson, Kevin E.,Agosta, William C.
, p. 1838 - 1843 (2007/10/02)
Irradiation of 9 leads to hydrogen abstraction by N(1) and fragmentation to 8 from a triplet with ET ～78 kcal/mol. Irradiation of 2-acylpyridines (10) leads to abstraction by both nitrogen and oxygen (cf. eq 4), with the same Stern-Volmer kqτ for the two processes. Irradiation of 2-acylpyrazines (11) can lead to abstraction by either nitrogen (φ27 0.77 from 11b) or oxygen (φ11a 0.95 from 11f)- 3-Acylpyridazine 12d is unreactive on direct irradiation or triplet sensitization with sensitizer ET ～70 kcal/mol; it furnishes a small amount of 12a on sensitization by acetone. Ketone 18 is recovered unchanged from irradiation under all conditions used with 12d. These observations suggest a correlation between the photochemistry of each of these compounds and the energy of the nπ* triplet of the heteroaromatic ring. The nature of the excited state(s) responsible for hydrogen abstraction by nitrogen and oxygen in these ketones is discussed.
