benzoxepin-2(3ff)-one, 3041-17-6; ethyl chlorocarbonate, 541-41-3; ethyl 4,5-dihydro-2(3H)-oxo-l-benzoxepin-3-carboxylate, 90913-47-6.

A total of 34 analogues of the biguanide PS-15 (5s), a prodrug of the diaminotriazine WR-99210 (8s), have been prepared. Several of them, such as 5b (PS-33) and 5m (PS-26), maintain or exceed the in vivo activity of PS-15 while not requiring the use of highly regulated starting materials. The putative diaminotriazine metabolites of these new analogues (compounds 8) have also been prepared and shown to maintain the activity against resistant P. falciparum strains. The structure-activity relationships of biguanides 5 and putative metabolites 8 are discussed.

Reactions of 3-aryl-3-bromodiazirines (11) with molten tetrabutylammonium fluoride at 25 O C provide 65-74% isolated yields of the novel corresponding 3-aryl-3-fluorodiazirines (12). Related reactions of 11 with tetrabutylammonium azide afford high yields of aryl nitriles. The latter reactions are believed to proceed through unstable intermediate 3-aryl-3-azidodiazirines (7). These reactions involve rate-determining formation of 7 and display kinetics which are first order in azide ion and bromodiazirine. The likely intermediacy of an aryldiazirinium bromide ion pair between 11 and 7 is supported by a combination of salt effect, leaving group effect, and Hammett studies. Molecular orbital calculations are employed to characterize azidodiazirines as well as the mode of their decomposition to nitriles. In particular, we consider the possible intermediacy of a 3-nitrenodiazirine or an azidocarbene.3H-Diazirines, 1, are important precursors for the thermal or photolytic generation of carbenes.'Z2 There are three principal syntheses of these compounds:* the oxidation of 1,2-unsubstituted

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