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Die im Titel genannte Verbindung (IIc) wird aus Bromacetylamino‐benoylpyridin (Ia) hergestellt.

A new synthesis of 7‐bromo‐1,3‐dihydro‐3‐hydroxy‐5‐(2′‐pyridyl)‐2H‐1,4‐benzodiazepin‐2‐one (5) is described. Starting from bromazepam (3), C(3) acylation with lead tetraacetate/potassium iodide in acetic acid affords 4, while its mild hydrolysis according to our recently described method (5) gives 5. Improved hexamine cyclization of 1 into 3, via quaternary hexaminium salt 2, is discussed, and identification of the intermediates 7 and 8 is performed. Compound 5 undergoes on melting, or on brief heating in glacial acetic acid, the thermal rearrangement into quinazolin‐2‐aldehyde (13), the structure of which is confirmed by oxidation into the ester 14, which in turn was hydrolyzed to the acid 15. The same compound (5) rearranges on heating with manganese(III) acetate in acetic acid into the 3‐amino‐2‐quinolone derivative 6. On heating in glacial acetic acid in the presence of lead tetraacetate/potassium iodide (or iodine), compound 4, in addition to giving the aldehyde 13, ester 14 and acid 15 rearrangement products, affords 1,2‐dihydroquinazolin‐2‐carboxylic acid 16.

Quaternization of (S)‐α‐bromophenylacetic acid amide (8) with hexamethylentetramine (hexamine) preceded with ca. 80% inversion of configuration. Accordingly, starting from the trimethylsilylester of N‐(S)‐(α‐bromo‐α‐phenylacetyl)‐6‐aminopenicillanic acid (4) quaternization with hexamine and subsequent hydrolysis afforded N‐(R)‐α‐phenylglycyl‐6‐aminopenicillanic acid (1, ampicillin). Some other model reactions have been investigated.