Novel synthesis of 5,11-dihydro-6H-pyrido[2,3-b]-[1,4]benzodiazepin-6-ones and related studies

5,11-Dihydro-6H-pyrido[2,3-6][1,4]benzodiazepin-6-one (1), a basic intermediate in the preparation of 11-α-aminoacetyl derivatives with important biological activities, has been obtained by a three-step synthesis starting from easily available isatoic anhydride and anhydro ornithine. Some model cyclisation reactions leading to 5-member ring derivatives 10 and 12 instead of 7-member ring analogues of 1 , are reported. Easy transformations of the tetrahydro congener of 1 , i.e., compound 4 into 19 , which actually represents a tetrahedral intermediate in the transformation of 5 into 4 , is noticed. Further rearrangement of 19 into spiro compound 20 , and return of the latter into 5 is described.