Dibenzo -diazocines

Dibenzodiazocine, 6,12-diamino-synthesis, 7, 683 Dibenzodiazocine, 6,12-dioxo-synthesis, 7, 683 Dibenzo[c,g][l,2]diazocine synthesis, 7, 672 Dibenzo[6,/][l,4]diazocine synthesis, 7, 675... 

Dibenzo[b,/][l,5]diazocine, tetrahydro-conformation, 7, 704 Dibenzo[b,/][l,4]diazocinediones synthesis, 7, 675 Dibenzodioxin, 2,7-dichloro-toxicity, 3, 992 Dibenzodioxin, hexachloro-toxicity, 3, 992 Dibenzodioxin, octachloro-toxicity, 3, 992... 

Tire tautomeric equilibrium of azocinones 65 has been studied by NMR, IR, and UV spectroscopy (90JHC1323). Dioxo derivatives of diazocines all exist as such, as illustrated by the analgetic 66 (75MI37) and the extensively studied dibenzo[h,/][l,4]diazocines (67) [81JCS(P1)988]. 

Reduction should result in l,2-dihydro-l,2-diazocine (2) which formally contains a cyclic, conj ugatcd 10 7r-electron system and potentially possesses aromatic character. To date, however, only the synthesis of a dibenzo derivative has been described (see Section 1.2.1.3.). 

Hydrazine reacts with biphenyl-2,2 -dicarbaldehyde (3, R = H). under elimination of nitrogen, to give phenanthrene,17 most probably not via the intermediate formation of a diazocine system. With other 2,2 -diacylbiphenyl compounds the expected dibenzo[[Pg.520]

Dibenzo[c,g][l, 2]diazocine (3) can be reduced with zinc in ethanol to the dihydro derivative 9.22 which formally exhibits a lOre-electron conjugation (see also ref 28). The UV and H NMR spectra of 9 indicate some resonance stabilization of the eight-membered ring. 

A solution of dibenzo[c,g][l,2]diazocine (206 mg, 1 mmol) and barium hydroxide octahydrate (0.5 g, 1.68 mmol) inluxing EtOH (50 mL) was treated with powdered zinc (0.5 g). Afterluxing for a few minutes, the solution became colorless and heating was discontinued. Dry ice (ca. 5 g) was added in small portions and the resulting suspension was filtered. The filtrate was evaporated to 20 mL and cooled to 0 C to afford colorless crystals yield 82 ing (40%) mp 168-169 C (dec.). 

A number of the purported syntheses of dibenzo[f>,/][l,4]diazocines in the literature have to be revised and the structure of the products corrected.1 Instead of the expected 1,4-diazocine derivatives 1, isoindolobenzimidazoles 2 are actually isolated, the formation of which requires a hydride shift after transannular attack of one imine group onto the other. 

Several dibenzo[e,g][l,4]diazocines 4 have been prepared by the condensation of biphenyl-2,2 -diamine derivatives 3 with 1,2-diones. The reaction proceeds upon simply melting the two components together, or byluxing in a high-boiling solvent. 

To a solution of dibenzo[6,/][l, 4]diazocine-6,l (5H. 2H)-dione (7 1.7 g, 7.5 mmol) in morpholine (10 mL) was added dropwise a cooled solution of TiClj. (3.13 g, 16.5 mmol) in anisole (10 mL). The mixture was then heated at 125 C for 2.5 h. poured into ice and extracted with CHC13. The organic layer was dried (Na2S04), concentrated in vacuo, and the residue passed through a column of neutral alumina (CHC13/ MeOH 95 5) yield 1.92 g (68 %). An analytical sample was obtained by recrystallization (CH2Cl2/ petro-leum ether) as a gray solid nip 240-243 C. 

The unsubstituted parent 1,5-diazocine (1) is hitherto unknown. Benzannulated systems, however, have been prepared, particularly dibenzo f>,/][l, 5]diazocine and its derivatives which have been intensively investigated due to their pharmacological properties. So far, all compounds synthesized show no evidence for delocalization of the 7t-electrons. One special review on the chemistry of 1,5-diazocines is available.1... 

If the reaction is carried out at higher temperatures with longer reaction times, the primarily formed product is reportedly transformed to an alternative dibenzo-1,5-diazocine, i.e. dibenzo-[A,g][l,5]diazocine-5,7(6//,12//)-dione (3).51... 

Treatment of dibenzo[A,/][l, 5]diazocine-6,12(5//,l l/7)-dione (2) with phosphorus pentachlor-ide transforms the amide functions into imidoyl chloride moieties.57... 

The dihydrazino derivative 6 can be transformed to the unsubstituted dibenzo[6,/][l, 5]diazocine (7) but the specific reaction conditions and yield were not reported.59... 

From the general structure of 1,2-diheterocines 1 with identical heteroatoms other than the scries with two nitrogen atoms (X — NR, which have already been discussed in Section 1.2. as they can be regarded as 1,2-dihydro-l, 2-diazocines), only one other example of such a 1,2-di-hcterocine system exists i.e. dibenzo derivative 4 containing the 1,2-dithiocin system 2.1... 

Dibenzo[c,g][l,2]diazocine (184) is a stable yellow crystalline solid obtained from dinitrobibenzyl by the steps shown (69JOC3237). Reduction of (184) gave the dihydro compound (183). 

Aside from the l,4-dihydro-l,4-diazocines (l,4-diaza[8]annulenes) discussed in Section 5.19.4.4.1, completely unsaturated 1,4-diazocines are represented in the literature only by benzo and dibenzo fused systems. 

The dibenzo[6,/][l,4]diazocine system (216) has been obtained by condensation of o- phenylenediamines with o-diaroylbenzenes in the presence of acid catalysts under very specific conditions (68CC1202, 75S246). In the presence of AICI3 or TsOH the diben-zodiazocines are formed in 70% yields different conditions lead to formation of o-amino-arylisoindoles. Racemization of an optically active aldehyde (216 R = CHO) has A[Pg.675]

Benzodiazocine and dibenzo[Z>,/][ 1,4]diazocine-diones (220) and (218) are obtained by condensation of diethyl succinate and phthalate, respectively, with o-phenylenediamine (69JOC2138). Contrary to an early report, the use of phthaloyl chloride leads to other products and not the tricyclic diazocine. The dibenzo derivative is also formed in the oxidation of diazabiphenylene (219) (78T495). Ring contraction of (218) occurs readily on heating or on treatment with PCI5 or with base. 

Condensations of anthranilic acid derivatives lead to the 6,12-diamino- and 6,12-dioxo-dibenzodiazocines, and the dichloro compound (279) is available from the latter (54JCS3429). Reduction of (279) via the dihydrazino compound was used to prepare the parent dibenzo[6,/][l,5]diazocine (280) (67CC1077). The NMR value (5 8.53 p.p.m.) of the 6(12) proton is indicative of the diazocine structure, presumably in a tub form, rather than the valence isomeric dibenzodiazapentalene (281). 

The tetrahydrodibenzo[6,/][l,4]diazocines (458) and the tetrahydrodibenzo[6,/]-[l,5]diazocines (459), which have two nitrogens in the heterocyclic ring, as well as their sulfur analogs (460) and (461) show conformational properties similar to those of the monoaza compound (456). Typical data are included in Table 3. The assignments of conformations and transition states for these dibenzo derivatives are supported by force-field calculations and by detailed dynamic NMR measurements <73JCS(Pl)205>. 

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