Karp GM. An Expeditious Route to Novel 1,4,2-Benzodiazaphosphepin-5-one 2-Oxide Analogues.
J Org Chem 1999;
64:8156-8160. [PMID:
11674731 DOI:
10.1021/jo9908400]
[Citation(s) in RCA: 16] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
A short and efficient synthesis of the novel 1,4,2-benzodiazaphosphepin-5-one 2-oxide ring system, a phosphonamidate isostere of the 1,4-benzodiazepine-2,5-dione system, has been carried out in good overall yield. The key step is the base-induced cyclization of (2-aminobenzamido)methylphosphonates 6a-c to the 1,4,2-benzodiazaphosphepin-5-one 2-oxides 7a-c. Alkylation of 7b with methyl iodide gives the expected N-methyl analogue 9. When a tandem one-pot cyclization/alkylation is carried out from 6b in the presence of excess base, the sole isolable product obtained is the phosphonate 13, presumably via ethanolysis of a transiently formed 9. Carrying out the tandem cyclization/alkylation in the absence of excess base, however, affords only 9. Thionation of 7 with Lawesson's reagent occurs at either the phosphonamidate oxygen (P-2) or the amide carbonyl (C-5) depending on the steric constraint of the N-4 substituent.
Collapse