Photochemische Reaktionen. 62. Mitteilung [1]. Die Photofragmentierung von O‐acetyljervin

On ultraviolet irradiation O‐acetyljervine ( 1 ) is subjected to several parallel fragmentations. From the complex reaction mixtures obtained in a variety of solvents (dioxan, tetrahydrofuran, acetonitrile, iso‐octane, benzene) the major alicyclic products 6 – 8 and the heterocyclic compounds 12 – 16 have been isolated. Products 6 – 8 undergo further photochemical changes, e.g. , decarbonylation of 7 to 9 and hydrolytic cleavage of 8 to 10 . These photofragmentations are initiated almost specifically upon selective π → π* excitation at 2537 Å with a quantum yield of Φ 2537 = 0.145 for conversion of starting material. Reaction upon irradiation in the long‐wavelength n → π* absorption band is very much less efficient (Φ 3660 = 0.611 · 10 −3 , both determinations for O‐trimethylsilyl‐jervine ( 2 ) in tetrahydrofuran). A high degree of photostability is observed also at 2537 Å on N‐protonation of O‐acetyljervine ( 1 ) in acetic acid. Furthermore, reactivity is greatly reduced for the N‐methyl ( 3 ) and N‐acetyl ( 4 ) derivatives in neutral solvents at 2537 Å. N‐Chloro‐O‐acetyljervine ( 5 ) in dioxan at 2537 Å gave preferentially O‐acetyljervine hydrochloride.