Dibenzo phenanthridines

The first compound containing a telluroazepine ring, ll-(4-methylphenyl) dibenzo[d,/][l,4]telluroazepine 62 was obtained in 21% yield upon heating p-xylene solution of 9-azido-9-(4-methylphenyl)telluroxanthene at 130-140°C (87KGS279). Other products of this pyrolitic process are the imine 63 (32% yield) and phenanthridine 64 (21% yield). Formation of the latter implies extrusion of the tellurium atom from dibenzotelluroazepine 62. 

In a reinvestigation of earlier work (33LA(505)103) by Diels and Alder, Acheson et al. (60JCS1691) established that the stable isomer obtained by addition of two moles of dimethyl acetylenedicarboxylate to one of pyridine was the 4/7-quinolizine (96) and that this with bromine was oxidized to a quinolizinium salt (97 Scheme 65). 4iT-Quinolizines obtained from isoquinoline (62JCS748) and phenanthridine (63JCS3888) were similarly aromatized to afford benzo[a]quinolizinium (98) and dibenzo[a,c]quinolizinium ions (99) respectively. 

The main interest in (212) and related dibenzo and dinaphtho compounds is in the conformational barrier to racemization of optically active derivatives, which requires deformation of the tub to the planar form. The compounds have proven to be optically stable at very high temperatures (64JCS2326). A minimum AH value of 71 kJ mol-1 has been calculated for racemization of the resolved 3,10-dicarboxylic esters of (212). Thermal decomposition sets in at 240 °C and leads to the phenanthridine (214) and benzonitrile, presumably via a diradical (213) (63JOC3007). 

A six-membered ring is formed in the reduction of 2-nitrobiphenyl-2 -carboxylic acid68 or 6,6 -dinitrobiphenyl-2,2 -dicarboxylic acid.69 In the former case a phenanthridine is formed, in the latter a 4,9-diazapyrene. Similarly, a seven-membered ring is obtained when 2-nitro-2 -isothiocyano-biphenyl (15) is reduced in acidic solution with the formation of 6-mercapto-dibenzo[d/]-l,3-diazepine 3-oxide (16)70 [Eq. (28)]. 

The thermolysis of 9-(p-tolyl)-9-azidotelluraxanthene 107 (X = N3) in refluxing xylene leads to ll-(p-tolyl)dibenzo[6/][l,4]tellurazepine 109, the first representative of the previously unknown tellurazepine heterocyclic system (87KGS279). Along with the tellurazepine 109 obtained in rather low (21%) yield, the arylimine 110 and phenanthridine 111 were also isolated as products of the thermolysis in 32% and 20% yield, respectively. 

Phenanthridine and Related Alkaloids Narciclasine Related Alkaloids Dibenzo[c,e]azocine Alkaloids —Tetracyclic Alkaloids... 

The mechanism of the related photorearrangement of heterocyclic N-oxides is still a matter for debate. Evidence that rearrangement of the phenanthridine N-oxides (48) to the N-substituted phenanthridones (49) and the dibenzo[d,f]-1,3-oxazepines (50) proceeds by way of biradical intermediates rather... 

Studies on benzo-fused analogs of 78 have also been reported. Solutions of unstable dibenzo[b,e]phosphabenzene (phosphaanthracene) (80, R = H)286 and dibenzo[6,d]phosphabenzene (phosphaphenanthrene) (81)287 have been prepared and examined by UV spectroscopy. The overall shape of the spectrum due to 80 (R = H) resembles that of anthracene rather than acridine, whereas that of 81 resembles the phenanthridine more closely than the phenanthrene spectrum. The absorptions of both 80 (R = H) and 81 show the typical strong bathochromic shifts relative to their nitrogen and carbocyclic analogs. 10-Phenyldibenzo[6, e]phospha-benzene (80, R = Ph)288 is more stable than its parent and shows similar UV absorption. 

The major adducts formed when phenanthridine is allowed to react with dimethyl acetylenedicarboxylate have been reformulated. - An initial Michael-type reaction gives the zwitterion (206) and succeeding reactions depend on the nature of the solvent. Adduct (207) is formed in anhydrous methanol by the addition of a proton and methoxide ion, while in benzene nucleophilic attack on the carbonyl group of a second ester molecule and subsequent cyclization provides 208. Alternatively, reaction at the triple bond of a second molecule of ester followed by ring closure of the new zwitterion gives 209. Other products related to 207 arise if the methanol contains water. 6-Methylphenanthridine with dimethyl acetylenedicarboxylate in benzene gives a mixture of the azepine (210) and tetramethyl 9a-methyl-9aA-dibenzo[a,c]quinolizine-6,7,8,9-tetracarboxylate. The... 

This methodology with some variations has been utilized in the synthesis of numerous heterocyclic systems, such as heterocycle-fused quinolinone derivatives [391], l,4-benzodiazepin-2-ones [392], benzo-, naphtho- and heterocycle-fused pyrrolo[2,l-c][l,4]diazepines [393], quinolinone or pyrrolidinone derivatives [394], dibenzo[fl,c]phenanthridines [395], thiazolo-fused quinolinones [396], isoindolinone and isoquinolin-2-one derivatives [397], indoline derivatives [398], 5-aroyl-pyrrolidinones [399,400], indazolone derivatives [401,402], substituted indolizidinones [403], 1-arylpyrrolopyrazinones [404], stmcturally diverse... 

Two neutral dibenzannulated systems are derived from pyridine the linear annu-lated acridine (1, dibenzo[h,e]pyridine) and the angular annulated phenanthridine (2, ... 

Churruca F, SanMartin R, Carril M, Urtiaga MK, Solans X, Tellitu I, Dominguez E (2005) Direct, two-step synthetic pathway to novel dibenzo[a,c]phenanthridines. J Org Chem 70 3178-3187... 

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