Cyclization agents/cyclizations methyl chloroformate

Clay den et al. [115] have reported the synthesis of spirocyclic p-lactams 176 (Scheme 41) by exo-cyclization of lithiated pyridine and quinoline carboxamides. The reaction of isonicotinamide or chlorinated isonicotinamide 175 with LDA at -40°C with addition of methyl chloroformate led to the formation of spirocyclic p-lactams 176 in good yields. Benzyl chloroformate, benzoyl chloride, methyl triflate can also be used as the effective acylating agents. In these type of reactions, lithiation of /V-benzyl pyridine and quinoline carboxamides to nitrogen provided... 

Phenylthiosemicarbazones cyclize easily to triazolo derivatives when heated alone or refluxed in high-boiling solvents. Phenylthiosemicarbazones 95 were refluxed in DMF and cyclized into 4,5-dihydro[l,2,4]tria-zolo[3,4-t/][l, 5]benzothiazepine-l(2tf)-thiones (96), which can exist either in the thioamidic or in the iminothiolic form. Infrared spectra showed that the thioamidic form seems to be preferred. By PTC alkylation of 96 with methyl iodide, ethyl chloroformate, or chloroacetic acid, the corresponding -substituted derivatives 97 were obtained (Scheme 28) (91MI1). Many of the compounds were cytotoxic and hence not screened further others were tested as antibacterial, antimycotic, and antiviral agents, but no appreciable activity was observed. 

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