Photoinduzierte 1, 3-dipolare Cycloaddition von 3-Phenyl-2H-azirinen an Azodicarbonsäure-diäthylester. 32. Mitteilung über Photoreaktionen

✍ Scribed by Paul Gilgen; Heinz Heimgartner; Hans Schmid

• Publisher: John Wiley and Sons
• Year: 1974
• Tongue: German
• Weight: 662 KB
• Volume: 57
• Category: Article
• ISSN: 0018-019X
• DOI: 10.1002/hlca.19740570514

✦ Synopsis

Abstract

Irradiation of 2, 2‐dimethyl‐3‐phenyl‐ (1a), 2, 3‐diphenyl‐2__H__‐azirine (1b) or the azirine‐precursors 1‐azido‐1‐phenyl‐propene (2a) and 1‐azido‐1‐phenyl‐ethylene (2b), respectively, in benzene in the presence of azodicarboxylic acid diethylester, yields the corresponding 1, 2‐carbethoxy‐3‐phenyl‐Δ^3^‐1, 2, 4‐triazolines 4a–d (Scheme 1).

Refluxing 4 (a, c or d) in 0, 2–0, 4M aqueous ethanolic potassium hydroxide leads to the formation of the 1‐carbethoxy‐3‐phenyl‐Δ^2^‐1, 2, 4‐triazolines 6 (a, c or d). Under the same conditions 4b is converted to 3, 5‐diphenyl‐1, 2, 4‐triazole (7b, Scheme 2). In 10M aqueous potassium hydroxide solution heating of either 4 (c or d) or 6 (c or d) yields the 3‐phenyl‐1, 2, 4‐triazoles 7 (c or d).

Photolysis of 1‐carbethoxy‐5, 5‐dimethyl‐3‐phenyl‐Δ^2^‐1, 2, 4‐triazoline (6a) in benzene in the presence of oxygen and trifluoroacetic acid methylester gives the 5‐methoxy‐2, 2‐dimethyl‐4‐phenyl‐5‐trifluoromethyl‐3‐oxazoline (13, Scheme 5). 5, 5‐Dimethyl‐3‐phenyl‐1, 2, 4‐triazole seems to be the intermediate, which on losing nitrogen gives the benzonitrile‐isopropylide (3a).