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Photocyclization of 2‐(dialkylamino)ethyl acetoacetates: Remote proton transfer and Stern‐Volmer quenching kinetics in the system involving two reactive excited states
Author(s) -
Hasegawa Tadashi,
Yasuda Naoko,
Yoshioka Michikazu
Publication year - 1996
Publication title -
journal of physical organic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.325
H-Index - 66
eISSN - 1099-1395
pISSN - 0894-3230
DOI - 10.1002/(sici)1099-1395(199604)9:4<221::aid-poc773>3.0.co;2-i
Subject(s) - chemistry , photochemistry , quenching (fluorescence) , excited state , kinetics , proton , fluorescence , physics , quantum mechanics , nuclear physics
Upon irradiation, 2‐(dibenzylamino)ethyl and 2‐( N ‐benzyl‐ N ‐methylamino)ethyl acetoacetate (1a and 1b) undergo photocyclization via remote proton transfer from the benzyl group to the acetyl carbonyl oxygen to give eight‐membered azalactones. Irradiation of the corresponding (diisopropylamino)‐ and (dimethylamino)ethyl esters gave no azalactones. Introduction of the methyl group on C‐2 of 1a brought about a complicated photoreaction, probably due to competition of α‐cleavage. The Stern‐Volmer plots for the photoreaction of 1a 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 1a. The triplet lifetime was determined to be 1·6 × 10 −8 s.