Photocyclization of 2-(dialkylamino)ethyl acetoacetates: Remote proton transfer and Stern-Volmer quenching kinetics in the system involving two reactive excited states
✍ Scribed by Tadashi Hasegawa; Naoko Yasuda; Michikazu Yoshioka
- Publisher
- John Wiley and Sons
- Year
- 1996
- Tongue
- English
- Weight
- 476 KB
- Volume
- 9
- Category
- Article
- ISSN
- 0894-3230
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✦ Synopsis
Upon irradiation, 2-(dibenzylamino)ethyl and 2-(N-benzyl-N-methylamino)ethyl acetoacetate (la and lb) undergo photocyclization via remote proton transfer from the benzyl group to the acetyl carbonyl oxygen to give eight-membered azalactones. Irradiation of the corresponding (diisopropy1amino)-and (dimethy1amino)ethyl esters gave no azalactones. Introduction of the methyl group on C-2 of l a brought about a complicated photoreaction, probably due to competition of a-cleavage. The Stern-Volmer plots for the photoreaction of la did not show the linear relationship, indicating that the photoreaction proceeds from two reactive excited states. The Stern-Volmer quenching equation for the system was obtained by applying the steady-state approximation and was used for the analysis of the photoreaction of la. The triplet lifetime was determined to be 1.6 x lO-'s.