Photochemische Cycloadditionen von 3‐Phenyl‐2H‐azirinen mit kumulierten Doppelbindungen. Vorläufige Mitteilung

Abstract

2 3 I11 72)Sunzmary. Irradiation of 2-methyl-(1 c ) and 2,2-ciimctliyl-3-pheny1-2H-azirine (1 d) in benzene solution in the prcscnce of carbon dioxidc yields 2-methyl-4-phenyl-(3 c ) and 2,2-dimethpl-4-phen~l-3-oxazolin-5-one (3 d), respcctively. Similar cycloadducts are observed (see table) when 2,3-diphenyl-ZH-azirinc (1 b) and 1 d are irradiated in the prcscnce of phcnylisocyanate, o-tolylisocyanate, phenylisothiocyanatc or cli-o-tolyl-carbotliiini~le, 3-Phenyl-2H-aairine 1 werden photocliemisch unter Losung der Cj2)-C(3)-Bindung in Benzonitri 1-methylenylide 2 uberfulirt (21 131 141. Eine besonders einheitliche Reaktiori beobachtete man bei der Bestrahlung (Pyrex-Filter) von 3-Phenyl-2H-1 2 20. Mitteilung iiher Photoreaktionen; 19. Mitteilung: [l].Eine ausfiihrliclie Mitteilung sol1 spater in dieser Zeitschriit crscheinen. 2,

Azirine photochemistry

“…19 the isomeric oxazolines 19 from 1 and ethyl cyanoformate, there is also formed the imidazole 20 from addition to the C=N bond in the expected regioselective manner.22 Thioesters lead to thiazolines20 (21) while isocyanates and ketenes produce heterocycles (22). 26 The photocycloaddition of arylazirines with a variety of multiple bonds proceeds in high yield and provides a convenient route for the synthesis of five-membered heterocyclic rings. Some of the dipolarophiles used in-clude azodicarboxylates,30 acid chlorides,31 vinylphosphonium salts,32 and p-quiñones.…”

Chemistry of oxazoles

“…121 When 1-azirines which are not substituted in the 3 position by a carbonyl functionality are subjected to the conditions of these photolyses reactions, C-C bond cleavage occurs to give a nitrile yllde intermediate.122 These nitrile ylides can undergo 1,3-dipolar additions to a variety of dipolarophiles.41 Schmid et al have studied the addition of the nitrile ylide 158 derived from the photolysis of 2,3-diphenyl-1-azirine (130) to cumulated double bonds and, in particular, to isocyanates. 123 The product of this reaction is 2,4-diphenyl-5-/V-phenylaminooxazole (159b). The initial addition product, the 5-iminooxazoline 159a, tautomerizes to 159b.…”

Zum Cycloadditionsverhalten von bis(trifluormethyl)substituierten Nitril-yliden [1]. Positionsselektivität und Regiochemie bei Abfangreaktionen mit Heterokumulenen / Cycloaddition Behaviour of Bis(trifluoromethyl) Substituted Nitrile Ylides [1]. Site Selectivity and Regiochemistry of Trapping Reactions with Heterocumulenes

“…Die Einbaurichtung des Heterokumulens in den Fünfring entspricht der des Addukts 12 [28]. Benzonitrilmethylide addieren Arylisocyanate ausschließlich über die CO-Doppelbindung unter Bildung der im obigen Fall nicht beobachteten 5-Imino-Zl 3 -oxazoline (11) [29].…”