Benzo-2,3-diazepines reduction

An intramolecular reaction with primary amine as the nucleophile that was prepared in situ by the reduction of the nitro group in pyrrole 1319 resulted in the pyrrolo[2,Tf]benzo[/ ]diazepine 1320, which indicates that the amino group reacts via condensation with the aldehyde group rather than via substitution of the chloro group (Equation 287) <2005T5831>. 

Dihydro-4H-benzo[/]pyrrolo[l,2-fl][l,4]diazepin-4-one 220 is a product of reductive cyclizations of ester nitrile 219a (R = COOMe, = CN), while amido... 

Contrary to the stable azepines and diazepines, benzo[ 7]benzofuro[2,3-/][l,4]-oxazepine 272 undergoes ring cleavage under reductive conditions in the acetic acid/acetic anhydride to afford open chain acetoxy amine 273 (Scheme 58, Section 3.2.2 (2001JHC383)). 

The reduction of benzo-1,4-diazepines was discussed in Part I, and the reduction of 3-hydroxy derivatives333-335 will be treated in Section V,B. Many papers and a review336 have treated the electroanalytical determination of benzo-1,4-diazepines. 

A sequence comprising an Oppenauer-type oxidation, intramolecular imine formation, and reduction, a process mediated by the iridium catalyst [Cp hG 2]2 and K2C03 in toluene at 120 °C for several days, afforded the structurally simple l-methyl-2,3,4,5-tetrahydro-177-benzo[l,4]diazepine in 68% yield from iV-(2-aminophenyl)-(Af-methylamino)propan-l-ol (Scheme 68) <2006TL6899>. 

Similar ring contractions in which the nitrogen-nitrogen bond is cleaved are found in the reductive ring contractions of pyridazines to pyrroles [148, 149], phthalazines to isoindoles [150], 5,6-diphenyl-1,2,4-triazinones to imidazolones [151], benzo-l,2,4-triazines to benzimidazoles [71], benzo-l,2,3-triazinone to indazolone [la, 152], benzo-l,2,3-triazin-3-oxide to indazole [la], benzo-2,3-diazepines to isoquinolines [153], benzo-l-pyrano-[4,3-e ]-as-triazin-3-one to benzopyranoimidazolone [154], and 2-methyl-4,5-dihydropyridazin-3-ones to pyrrolin-2-ones [155]. 

Benzo-l,2,4,5-tetrahydro-l,5-diazepines (333) may be obtained by the NBH reduction of the benzo-l,5-diazepinium chloride precursors 332. Yields in excess of 90% are claimed. When the reduction was carried out in dimethylformamide, 2,4-dimethyl-1,5-dihydro-6,7-benzo-1,5-diazepine (334) was obtained. Additional work has shown that this reduction occurs stereoselectively, giving c -tetrahydro-l,5-diazepines. ... 

SCHEME 7.36 Synthesis of benzo-l,4-diazepin-2,5-diones 88 under Ugi and reductive conditions. 

---