Diazeti dines

Fromm12 proposed that l,3-diazetidine-2-thiones were the products of the reaction between dithiobiurets and aldehydes or ketones, which he called aldurets and keturets, respectively. These structures were subsequently shown to be hexahydrotriazines by Fairfull and Peak.13 Kurzer,3 in his review of dithiobiurets, summarized the structural work on aldurets and keturets. Dixon and Taylor14 claimed that 1,3-diazeti-dine-2-thiones wrere the products of the acid-catalyzed treatment of... 

Carbodiimides undergo [2+2] cycloaddition reactions to furnish l,3-disubstituted-2,4-bisalkyl or arylimino-l,3-diazeti-dine. For example, dibenzyl carbodiimides undergo dimerization to yield l,3-diazetidin-2,4-diimines 296 on heating. The reaction can be catalyzed by the addition of tributylphosphine (1%) (Equation 36) <1940CB1114, 1968CB174>. 

Excess BClg-gas carried by N2 at -60° into a soln. of phenyl isocyanate in anhydrous toluene or chloroform, and after 4 hrs. at 0° treated with ice-water N,N -diphenylallophanoyl chloride (Y 70%) in anhydrous toluene treated with pyridine, and the product isolated after 12 hrs. at 20° l,3-dipheny -l,3-diazeti-dine-2,4-dione (Y 95%). F. e., also ring closure in chloroform, s. H. Helfert and E. Fahr, Ang. Ch. 82, 362 (1970). 

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