Furo-l,2-diazepines

The photolysis of quinoline TV-imides (262) (which are in equilibrium with their dimers) (77JOC1856) gives IH- 1,2-benzodiazepines (263). Reactions of this type have also provided routes to pyrido-, thieno- and furo-l,2-diazepines (79CPB2183,79H( 12)471). 

C- H coupling constants, 4, 569 crystal data, 3, 623 mass spectra, 3, 610 structure, 4, 541 Furo[l,2]diazepines synthesis, 7, 598 Furo[ 1,3]diazepines synthesis, 7, 607 Furodysin... 

Furo[2,3-6]pyridine was aminated in good yield by treatment with O-mesitylenesulfonylhydroxyl-amine to afford furo[2,3-6]pyridinium mesitylenesulfonate (31). Treatment with methanolic potassium hydroxide forms an ylide in situ which, upon irradiation, generated furo[2,3-c]l//-l,2-diazepine (32) and a minor amount of 2-aminofuro[2,3-6]pyridine (33) (Scheme 5). This material gradually decomposes on standing <78H(9)62i, 79CPB2183). 

Some time ago the Streith ring-expansion of pyridinium AT-imides was extended to the synthesis of lf/-l,2-benzodiazepines from quinoline N-imides. The full report has now appeared of the further extension of this valuable synthetic route to the preparation of the following previously unknown 1,2-diazepines, annelated to heteroaromatic rings pyrido[3,2-c]-,pyrido[2,3-c]-,thieno[2,3-c]-, thieno[3,2-c]-, and furo[2,3-c]-l//-l,2-diazepines e.g., (61) from (59), presumably via (60)." A similar attempt to prepare pyrrolodiazepines was not successful. These 1//-tautomers were converted into the 3//-l,2-diazepines by reduction with lithium aluminium hydride and then dehydrogenation with 4-phenyl-l,2,4-triazoline-3,5-dione. ... 

The reaction of ethyl 2-phenyl-4//-furo[3,2-/>]pyrrole-5-carboxylate (94) with 2-nitrobenzyl-oromide afforded ethyl 4-(2-nitrobenzyl)-2-phenylfuro[3,2-6]pyrrole-5-carboxylate (269) under conditions of phase transfer catalysis by utilization of sodium carbonate and tetrabutylammonium bromide. This product (269) was hydrogenated using palladium-on-charcoal catalyst to give the amine (270), which cyclized in the presence of 2-hydroxypyridine to give 2-phenylfuro[2, 3 4,5]pyrrolo[2,l-c]benzo[l,4]diazepin-l 1-one (271) <92CCC1487>. 

Cumulative Index of Heterocyclic Systems Furo[2,3-e][l,4]diazepine (850)... 

The susceptibility of the pyrrole ring to electrophilic attack has been used in the synthesis of pyrrolo-fused 1,4-diazepines, for example, A-(3-acetylaminopropyI)-3-methyl indole underwent a Bischler-Napierelski-type cyclodehydration on treatment with phosphorous oxychloride in benzene to give ll-methyl-4,5-dihydro-3ff-l,4-diazepine[l,2-a]indole <91IJC(B)1018>. In another example the acyl azide (143) cyclized to the furo[2,3-e]pyrrolo[l,2-a]-l,4-diazepine-9-one (144) (Scheme 25) <92JHC1507>. 

Moreover, Tu, li, and coworkers [89] presented a regioselective [4-I-2-I-1] domino cychzation for the synthesis of spiro-substituted benzo[fc]furo[3,4-e][l,4]diazepine... 

Cheng C, Jiang B, Tu SJ, Li G (2011) [4 + 2+1] Domino cyelization in water for chemo- and regioselective synthesis of spiro-substituted benzo[6]furo[3,4-e][l,4]diazepine derivatives. 

The fully-unsaturated 1,3-benzodiazepine 310 is formed by a photoreaction of the 1-substituted isoquinoline 7V-imide 309 (Scheme 169) <1980CPB2602>. The same principle has been applied to prepare thieno-, furo-, and pyrrolo-fused 1,3-diazepines <1980CC454, 1981CPB1539>. The imidazolo-fused l,3-benzodiazepin-2-ones 313 can be prepared by the reaction of 5-amino-4-(cyanoformimidoyl)imidazoles 311 with tosyl isocyanate. The mechanism of this reaction includes a 1-exo-dig cyclization of intermediates 312 followed by a Dimroth rearrangement to give the thermodynamic products 313 (Scheme 170) <1996JHC855, CHEC-III(13.05.9.2.2)174>. 

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