1.5- Diazocine-2,6-diones

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. 

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. 

Phenanthrene-9,10-dione 7 gives 1,4-diazocine 8 on reaction with biphenyl-2,2 -diamine.30... 

Benzocyclobutene-l,2-dione (11) can be condensed with benzene-1.2-diamine to provide an annulated quinoxaline (cf. Houben-Weyl, Vol. E9b/Part 2, p203), which on oxidation with hydrogen peroxide in acetic acid leads to the 1,4-diazocine derivative 12.34... 

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. 

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... 

A suspension of 200 mg (0.56 mmol) of 1.4-diben7yl-2,3,6,7-tctrahydro-6,7-dihydroxy-l,4-diazocine-5,8-(l//.4//)-dione in 5 mL of dry CH,CI, is treated with 98 j.iL (0.56 mmol) of tri-2-propenylborane at 23 °C. The suspension becomes a clear solution within a few minutes. The solution is stirred for 3 h before being concentrated in vacuo with exclusion of moisture. The resulting white foam is stripped overnight at 0.1 Torr to give the reagent that is used directly in reactions with aldehydes. 

Rose-Bengal sensitized photooxygenation of cyclic tryptophan derivative 119 gave l,3-diazocine-2,6-dione 120 (76H53). Murato and coworkers reductively cleaved / -carboline derivative 121 and isolated the novel diazocinoindole 122 (77CPB1559). 

The enantiomerization of 6,7-dihydro-dibenzo[///][l,2]diazocine-5,8-dione 2 was investigated using quantum-mechanical methods. At the density functional theory (DFT) B3LYP/6-31G(d,p) level, two enantiomeric -symmetric transition states (TSs) and two enantiomeric pathways were found with a calculated barrier of 155.6 kj mol-1. The pathways can be divided into two steps one involving primarily inversion of the amidic bridge and the other movement of the aromatic rings <2004TA537>. 

Bridged 1,2-diazocines 32a-c, obtained from cyclooctadienes and 4-phenyl-l,2,4-triazoline-3,5-dione, were useful intermediates for the synthesis of diaminopolyols, core units of various bioactive aminoglycoside antibiotics and antiviral... 

Triazolo-diazocine 12 was obtained through a [6+2] cycloaddition of cycloocta-l,3-dione and 4-pyren-l-yl-l,2,4-triazole-3,5-dione 80. Such a triazole derivative was obtained by in situ oxidation of l,2,4-triazolidine-3,5-dione 81, which was in turn obtained by reacting isocyanates and semicarbazides, followed by base-catalyzed cyclization... 

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