1.3- Diazetidines

Diazetidine-3,4-dione, 1,2-di-t-butyl-electrophilic reactions, 7, 460 spectroscopy, 7, 454... 

Diazetidines applications, 7, 483 electrophilic reaction, 7, 460 nitrogen inversion, 7, 10 nucleophilic reactions, 7, 462 photochemical reactions, 7, 456-457 reductive cleavage, 7, 465 spectroscopy, 7, 451-454 structure, 7, 451... 

Uretidinedione — see l,3-Diazetidine-2,4-dione 2-Uretidinone, 1,3-diphenyl-4-(phenylimino)-synthesis, 7, 474 Urgothianine, 5, 498 Urie acid... 

A ring-opening reaction of 1,3-diazetidines 1004 with thiobenzamide gave [l,3,4]thiadiazolo[2,3-c][l,2,4]triazine 1005 [89JCR(S)140] (Scheme 186). 

Making use of the same reaction principle, disubstituted ketenes 66 have been reacted with aldehydes 80 to form p-lactones 81 [100], with diazo-compounds 82 to form 1,2-diazetidin-3-ones 83 [101] and with nitroso-compounds 84 to form 1,2-oxazetidin-3-ones 85 as precursors of a-hydroxy carboxylic acids (Fig. 42) [102],... 

Indene, however, does give four-membered ring adducts with PTAD,69 and phthalazine-t,4-dione.70 The reaction with PTAD proceeds stepwise via the dipolar intermediate 43, which was trapped in the presence of water to give 44, under conditions in which the 1,2-diazetidine (45) was not opened by water to 44 (Scheme 5).69 Hydrolytic cleavage of the triazole ring in 45 using potassium rm-butoxide in wet dimethyl sulfoxide, followed by... 

Carbocyclic compounds containing an unsubstituted exocyclic methylene group give 1,2-diazetidines with PTAD. Methylene adamantane gives the adduct 47,8 5 and the methylene cyclopropane (48, R = H) gave the 1,2-diazetidine 49.86 The phenyl-substituted compound (48, R = Ph) behaved similarly to styrene and gave a 2 1 adduct with PTAD (see Section IV,D,1). 

A 1,2-diazetidine has been proposed as an intermediate in the reaction of pyridazine-3,6-dione (12) with styrene.87 The observed product was thought to arise from addition of water to the 1,2-diazetidine, although the alternative more likely explanation involving a dipolar intermediate (cf. Scheme 5) was apparently not considered. In the photochemical reaction of styrene with DEAZD, a 1,2-diazetidine structure was tentatively assigned to a minor product.88 Attempted photochemical [2 + 2] cycloaddition of DEAZD to other olefins failed to give any 1,2-diazetidines.88... 

In the reaction of the cis-disubstituted olefins 53 (X = S, R = Me) and 53 (X = O, R = D) with DMAZD, only the cis- 1,2-diazetidines are formed.94,95 The observation of this stereospecificity, the isotope effects and lack of solvent dependence would seem to support a concerted mechanism, although the workers prefer to explain the isotope effects by a stepwise mechanism involving a dipolar intermediate, similar to that already described for the reaction of PTAD with indene.95 Other workers claim that the reaction is... 

ADC compounds add to allenes to give 3-methylene-1,2-diazetidines. Tetramethoxyallene adds to DEAZD and to PTAD to give adducts 59 and 60 in 43 and 69% yield.99 DEAZD adds to the 2,3-double bond of 1,1-difluoroallene (in poor yield), in contrast to maleic anhydride which adds to the 1,2-double bond.100 o... 

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