97388-87-9Relevant articles and documents
Cycloaddition of Benzodiazepine Nitrones to Alkynes: Synthesis and X-Ray Analysis of Some Tricyclic Quinoxalines.
Capozzi, Giuseppe,Ottana, Rosaria,Romeo, Giovanni,Sindona, Giovanni,Uccella, Nicola,Valle, Giovanni
, p. 2026 - 2048 (2007/10/02)
7-Chloro-2-methylamino-5-phenyl-3H-benzodiazepine 4-oxide (chlordiazepoxide) undergoes 1,3-dipolar cycloaddition to electron-deficient alkynes yielding condensed 4-isoxazoline benzodiazepine and pyrrole-fused quinoxaline derivatives.The structure of the reaction products was determined by analytical and spectroscopic methods with the application of LIS and X-ray analysis.The overall process involves an initial addition step, the rate determing one, followed by ring-opening of the 4-isoxazoline intermediate, ring-contraction of the seven-membered nucleus to the quinoxaline system, and subsequent condensation to the tricyclic derivatives.The suitable stereochemistry and the N-O vinylic functionality, forming a good leaving group in the 4-isoxazolines, drive the 1,2-bond migration from carbon to the electron-deficient nitrogen atom of the benzodiazepine ring.The energetics of the condensation steps are discussed on the basis of thermochemical considerations postulating a kinetic effect for the pyrrole-ring closure due to the extended delocalization of the enolate intermediate.