3//-l,2-Diazepine

Equilibrium Mixture of 5,7-Dimethyl-3//-l, 2-diazepine (7 a) and 3,5-Dimethyl-3W-1,2-diazepine (8 a) Typical Procedure 104... 

Irradiation of 4-methyl-5,7-diphenyl-3//-l,2-diazepine at — 70°C gives 5-methyl-l,6-diphenyl-4,6a-dihydro[l,2]diazeto[l,4-a]pyrrole in 83% yield.105... 

Toluenesulfonyl-3,4-dihydro-l,2-diazepines (24 R = Ts) react with alkoxides under aprotic conditions at ca. 100 °C to provide a synthesis of 3//-l,2-diazepines (25). 

Reaction of tosylhydrazide with -unsaturated ketones, followed by dehydrotoluenesulfonylation affords 3//-l,2-diazepines (Scheme 85) <1984J(P1)1581>. The tautomeric products 170 and 171 are in dynamic equilibrium at room temperature but can be separated by high-pressure liquid chromatography at 6C. 

New examples of well established photo-induced rearrangements arising by electrocyclic pathways have been reported. A classification for such processes in systems containing heteroatoms has been proposed. 1/f-l-Benzazepines are readily converted on irradiation in tetrahydrofuran into dihydrocyclo-but[6]indoles, whereas the 4,6a-dihydro[l,2]diazeto[l,4-a]pyrroles (18) are formed preferentially on irradiation of the 3//-l,2-diazepines (19). A high yield... 

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. ... 

Treatment of 1//-1,2-benzodiazepines (75) with lead tetra-acetate (LTA) gives the previously unknown 5/T-tautomers (76) together with some 3-vinyl-indazoles/ The latter probably derive from the 3//-tautomer (77), as discussed below (refs. 48 and 49). The 5//-1,2-benzodiazepines are less stable than the 3H-and lif-tautomers and can be isomerized to the latter with base they also readily add acetic acid or methanol to give 1,4-adducts. Photolysis of (76) gives 3-acetoxyindole, most likely via (iris + iris) ring-closure of the diazabutadiene unit (cf. 3//-l,2-diazepine and 1//-2,3-benzodiazepines) and extrusion of RCN. 

Pyrazolo[3,4-d][l,2]diazepines synthesis, 7, 597 Pyrazolop, 4- 6][ 1,4]diazepines synthesis, 5, 272 Pyrazolo[l, 4]diazepinones as anticonvulsant, 1, 170 Pyrazolo[2,3-e]diazepinones synthesis, 5, 272 1 H-Pyrazolo[l,5-6]imidazoles synthesis, 6, 992 Pyrazolo[2,3-a]imidazoles biological activity, 6, 1024 Pyrazolo[2,3-c]imidazoles reactions, 6, 1041 synthesis, 6, 1047 Pyrazolo[2,3-imidazoles synthesis, 6, 991 Pyrazolo[3,2- njisoquinolines synthesis, 5, 339 Pyrazolop, 4-c]isoquinolines synthesis, 5, 273 Pyrazolonaphthyri dines synthesis, 5, 339 Pyrazolone, diazophotolysis, 5, 252 Pyrazolone, 4,4-dihalo-rearrangements, 5, 250 Pyrazolone, ethoxy-hydrazinolysis, 5, 253 Pyrazolone, 4-halo-... 

Thieno[ 1,2,3]diazaborines, dihydro-bromination, 1, 656 deuteration, 1, 658 iodination, 1, 656 nitration, 1, 656 nucleophilic substitution copper-promoted, 1, 658 Thienodiazepines synthesis, 7, 595 Thieno[ 1,2]diazepines synthesis, 7, 598 Thieno[2,3-d][l, 2]diazepines synthesis, 4, 749 Thieno[3,2-d][l,2]diazepines synthesis, 4, 749 Thieno[ 1,3]diazepines synthesis, 7, 607 Thieno[ 1,4]diazepinones as anticonvulsants, 1, 170 Thieno[3,4-d][l,3]dioxol-2-one, 4,6-diphenyl-... 

Certain 1,5 diazabicyclo[3 3 0]oct-2-enes can be transformed unexpectedly into 4//-5,5-dihydro-l, 2 diazepines on heating [209] 1,5-Dipoles formed on heating of l,5-diazabicyclo[3 3 0]oct-2-enes [210] can be trapped with olefins to give [3+2] cycloadducts At elevated temperatures, they undergo a [3+2] cycloreversion Tins reaction sequence offers a simple route to dienes with interesting substitution patterns, for example, 1,1 bis(trifluoromethyl)-l,3-butadiene [211] The [3+2] cycloadducts that arise from the reaction of the 1,5 dipoles with acetylenes undergo... 

A well-studied case of tautomerism is that of l,2-diazepin-4-ones tautomers 47a and 47b were characterized by NMR, the former being the most stable (85JOC2141). 3,5-Dihydro-4//-2,3-benzodiazepin-4-ones exist as 48a and not as 4-hydroxy tautomers 48b (74JHC401). 

Cyclization of 6-diethylaminohex-3-en-5-yn-2-one (375), an ynaminoketone vinylog, with hydrazine yields 3-diethylamino-7-methyl-5//-l,2-diazepine (375) (97DIS). 

This reaction can also be used for the synthesis of substituted 1-benzoxepins with one modification instead of the 4/T-benzopyran the 2/7-isomer must be used. 2-[Diazo(phosphoryl)meth-yl]-2//-benzopyrans decompose in the presence of ))3-allylpalladium chloride dimer with elimination of nitrogen to give 1-benzoxepins 2.192 In some cases, the reaction takes a different course and gives 2-methylene-2//-benzopyrans 3.192 In this respect, the bicyclic system behaves differently to the monocyclic diazo(pyranyl)methane. The 2-isomers of the latter structure could not be isolated and gave l//-l,2-diazepines.190 The 4//-benzopyrans do not form benzoxepins but undergo an intramolecular [2+1] cycloaddition to 3,4-dihydro-2,3,4-metheno-2//-ben-... 

Ethyl 3-Acetyl-4,6-dimethyl-1//-l,2-diazepine-7-carboxylate (2a) Typical Procedure 71... 

Ethyl 1//-l,2-diazepine-l-carboxylate (0.50g, 3.1 mmol) in benzene (100 mL) was treated with Fe2(CO)9 (1.50 g, 4.1 mmol) and the mixture was vigorously agitated at 20 C under N2. The mixture was filtered, the filtrate was evaporated and the residue was chromatographed (silica gel, EtOAc/cyclohexane 2 3) to give the product, which was sublimed at 60°C/0.04Torr yellow crystals mp 115 C. (The yield was not reported.)... 

Isopropyl l//-l,2-diazepine-l-carboxylate similarly gives tricarbonyl(4-7t/-l-isopropoxycar-bonyl-l//-1,2-diazepine)ironin45% yield (mp 106"C)and l-acetyl-3-methyl-l//-l,2-diazepine gives the corresponding iron tricarbonyl complex in 92% yield (mp 110 C).77... 

Triphenyl-47/-l,2-diazepine is transformed into a mixture of 2,4,6-triphenylpyridine and the rearranged diazepines 3,5,6-triphenyl-4//-l,2-diazepine (28) and 3,5,6-triphenyl-l H-, 2-di-azepine (29) on prolonged heating.111... 

The 1-benzoyl-l//-l,2-diazepines 3 undergo loss of the A -benzoyl group and ring contraction to provide the pyridines 4 in refluxing xylene (see Houben-Weyl, Vol. E7b, p 519).93... 

Acvl-1 //-l, 2-diazepines 5 are converted photochemically into 2,3-diazabicyclo[3.2.0]hepta-dienes 6 (see Houben-Weyl, Vol. 4/5a, p 585).94... 

Under acidic conditions, dienone tosylhydrazones 5 cyclize to 1 -tosyl-6,7-dihydro-l//-l,2-diazepines 6,l04a which on treatment with sodium ethoxide eliminate the elements of/Moluenesul-finic acid to yield an equilibrium mixture of the tautomeric 3//-1,2-diazepines 7 and 8.104b... 

Dimethyl-l-tosyl-6,7-dihydro-l//-l,2-diazepine (1.164 g, 4.19 mmol) was added to NaOEt prepared from Na (0.16 g, 6.96 m-atom) and EtOH (20 mL). The solvent was removed on a rotary evaporator at... 

Dimethyl 5,6-Diphenyl-4A/-l,2-diazepine-3,7-diearboxylate (2a) Typical Procedure 107... 

Triarylpyrylium salts react with hydrazine to give 4//-l,2-diazepines 472-1°s,ioo vja g unstable intermediates 3.110 The reaction fails with pyrylium salts containing alkyl groups in positions 2 and 6, with the exception of 2,4,6-tri-tert-butylpyrylium perchlorate. In some cases it is advantageous to use a thiapyrylium salt in place of the pyrylium salt. Selected examples are given. 

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