Chalcone derivatives, aziridines

The reaction of 2 -benzyloxychalcone dibromides (605) with ammonia gives a chalcone aziridine (606). Following conversion to the (V-benzoyl derivative, acid hydrolysis removed the protecting group at C-2 and a 3-aminoflavanone results (Scheme 230) (73ACH(76>95). 

Synthesis of annelated diazepines based on unsaturated aromatic diazepines may involve the preliminary transformation of ketones into the corresponding l,3-diaryl-2,3-dibromopropane-3-ones (chalcone dibromides). The interaction between o-PDA or some of its substituted analogues with chalcone dibromides leads to the formation of aziridine derivatives [64] (see Chap. 1). However, in the case of 4-nitro-o-PDA, either azirenoquinoxalynes 53 or benzodiazepine derivatives 54 may be obtained depending on the reaction conditions [65] (Scheme 4.15). Diazepine derivatives 56 are obtained by the condensation of chalcone dibromides 51 with 5,6-diamino-1,3-dimethyluracil 55 [66], but aziridine derivatives are not isolated in this reaction. It should be noted that compounds 54 and 56 are formed owing to cyclization of the intermediate (3-enaminoketones [65, 66, 67] and are easily isolated from the reaction mixture. 

Thiophen-2-aldehyde has been used in a preparatively useful modification of the Knoevenagel reaction in which TiCU and a tertiary amine in tetrahydrofuran were used in order to achieve facile condensation with ethyl acetoacetate and ethyl nitroacetate. The reaction of the dibromo-derivative (155) obtained from the corresponding chalcone with cyclo-hexylamine gave the 2-(2-thienyl)aziridine (156). The reaction of (156)... 

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