1.2- Diazetidine fused derivatives

Photoextrusion of nitrogen (70JA6218) and carbon monoxide (71JCS(C)2920> has been used to prepare 1,2-diazetidines (Scheme 123). Photoisomerization has alternately been reported to give fused derivatives of 1,2-diazetidines (Scheme 124) (68CC686,69JA2818). 

Photoisomerization has been reported to give fused derivatives of 1,2-diazetidines (Scheme 27) (68CC686, 69JA2818). 

Various fused derivatives of 1,2-diazetidines 193 can be prepared via cycloaddition reactions of the dienophile 192 (Scheme 117) (also see Section 4.3.2.2.1) C20010L3185, CHEC-III(2.13.9.4.2)675>. 

Diazetidines. A saturated four-membered ring containing two adjacent nitrogen atoms is named a 1,2-diazetidine 1. When the two nitrogen atoms and the two carbon atoms are alternatively present in the four-membered ring, it is named a 1,3-diazetidine 2, which is also known as uretidine. Fused multinuclear heterocyclic systems are known as diazacyclobutane derivatives. For example, 3,4-benzo-l,2-diazetidine is referred to as l,2-diaza-3,4-benzocyclobutane 3. 

The Wittig-type reactions of iminophosphoranes with isocyanates and related compounds have also been extensively used in heterocyclic synthesis. Examples include the preparations of the mesoionic [l,3,4]thiadiazolo[2,3-c][l,2,4]triazines (210) from (209), 0 bicyclic guanidines, e.g. (212), from (211), naphthypyridines (215), (216), and (217) from (213) and (214), 2 pyrido[l,2-f]pyrimido-[4,5-d)pyrimidines (218), 7H-pyrido-[4,3-c]- (219) and 10H-pyrido[3,4-b]- (220) carbazoles, tricyclic fused 2,4-diimino-l,3-diazetidines (222) from the bisiminophosphorane (221), benzotriazepines (225) from (223) and (224), 6 and mesoionic thiazolo-[2,3-b]-1,3,4-thiadiazoles (227) and N,N-bisheteroarylamines from the iminophosphorane (226), derived from 3-amino-4-phenylthiazole-2(3H)-thione. The carbodiimides (229), prepared from the iminophosphorane (228), can be converted into quinolines or a-carboline derivatives depending on the nature of the isocyanate used in the reaction with (228) and the reactions of iminophosphoranes (230) and (231) with aryl and styryl isocyanates provide one-pot syntheses of quinoline, a-carboline, and quinindoline derivatives. 9... 

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