Phenanthrene-fused azo-ene-ynes: synthesis of dibenzo[f,h]cinnoline and dibenzo[e,g]isoindazole derivatives

The cyclization reactions of a phenanthreno-fused azo-ene-yne compound have been studied both experimentally and computationally. Experimental results show that this system is prone to dimerization, more so than previously studied naphthalene- and benzene-based analogues. Calculations reveal that pyrazoles and arene-fused pyrazoles strongly stabilize carbenes in the 5-position through "coarctate conjugation", suggesting a stationary concentration of the carbenes/carbenoids during cyclization that is high enough for dimerization.     

Asymmetric synthesis of dibenzo[b,d]azepines by Cu-catalyzed reductive or borylative cyclization

A copper-catalyzed asymmetric intramolecular reductive cyclization for the synthesis of dibenzo[b,d]azepines is described. Use of 2′-vinyl-biaryl-2-imines as substrates and in situ formed [Cu^I/(Ph-BPE)] as the catalyst enables the synthesis of 7-membered bridged biarylamines containing both central and axial stereogenic elements in high yields (up to 98%) and with excellent diastereo- and enantioselectivities (>20 : 1 d.r., up to 99% ee). Moreover, the same catalyst was found to facilitate a related borylative cyclization to afford versatile boronic ester derivatives. Both reactions proceed under mild conditions (rt) and are applicable to a variety of substituted aromatic and heterocyclic derivatives.

Dibenzo[b,d]azepines featuring axially chiral 7-member-bridged biaryls have been prepared by asymmetric reductive or borylative cyclizations using copper catalysis.     

Synthesis of 5,12-diazadibenz[a,h]anthracene

5, 12-Diazadibenz[a,h]anthracene ( 20 ) was synthesized in 21% overall yield for seven steps. Salient features of the synthesis include the initial, one-step conversion of trans, trans-1,4-bis-(β-nitrovinyl)benzene into 2,2″-dinitro-p-terphenyl by Diels-Alder condensation plus elimination, monocyclization of the derived 2,2″-diformylamino-p-terphenyl to give 8-(2-amino-1-phenyl)-phenanthridine ( 10 ) in the presence of fortified polyphosphoric acid, and accomplishment of a second cyclization step only after reduction of the heteroring in 10 (by means of diisobutyl-aluminum hydride) plus formylation. The 6-methyl and 6,13-dimethyl derivatives of 20 were prepared similarly.     

Dihydrodiols and diol epoxides of dibenzo[a,i]-and [a,h]pyrene

Syntheses of dihydrodiols and highly mutagenic diol epoxides of the carcinogenic polycyclic aromatic hydrocarbons dibenzo[a,i]-and [a,h]pyrene are described.     

Stereoselective syn epoxidation of the dihydrodiols of dibenz[a,h] anthracene and 7-methylbenz[a] anthracene

Epoxidation of the bay region dihydrodiols of the title hydrocarbons affords stereoselectively the corresponding syn diol epoxides rather than the anticipated isomeric anti diol epoxides, indicative of a dominant cis-directing effect of the benzylic vs the allylic axial hydroxyl groups.     

A comprehensive study of isoskeletal analogs of dibenzo[a,c]anthracene

While reviewing the chemistry of cyclopentadienone derivatives and aza isoskeletal analogs of dibenzo[a,c]anthracene, additional molecular orbital (MO) and spectroscopic results and insights are presented. The MO tendency for coplanarity of phenyl substituents on benzenoids is demonstrated. Perpendicularly oriented phenyl substituents resulting from steric interactions strongly shield appropriately situated protons in NMR spectra. The principles of alternating polarity and parallel correspondence in conjunction with MO methods are used to relatively order aza arene isoskeletal analogs according to their chemical properties. Since less than 1.87% of the isoskeletal analogs of benzo[a,c]-anthracene have been reported, this summary work will help one to forecast the major chemical properties of those not yet synthesized.A preliminary account of this work was presented at the 23rd ACS Midwest Regional Meeting, University of Iowa, Iowa City, Nov. 17, 1988     

Synthesis of bisimines of pyrene and dibenz[a,h]anthracene

The preparation of 3b,4a,7b,8a-tetrahydro-4H,8H-pyreno[4,5-b:9,10-b']bisazirine and of 1a,6b,7a,12b-tetrahydro-1H,7H-dibenz[3,4:7,8]anthra[1,2-b:5,6-b']bisazirine is described. The corresponding diepoxides were reacted with sodium azide in aqueous acetone and the mixtures of trans-azido alcohols, so formed, were cyclized by tri-n-butylphosphine.     

Synthesis of the dibenzo[f,h]phthalazine and dibenzo[f,h]cinnoline skeleton via a ‘Suzuki-Pd-catalyzed intramolecular arylation’ and a ‘Suzuki-Pschorr’ approach

Palladium-catalyzed intramolecular arylation of 2-benzyl-5-(2-bromophenyl)-4-phenylpyridazin-3(2H)-one yielded hitherto unknown 2-benzyldibenzo[f,h]phthalazin-1(2H)-one. The synthesis of this new tetracyclic pyridazinone from 2-benzyl-5-(2-aminophenyl)-4-phenylpyridazin-3(2H)-one via a Pschorr type reaction was also investigated. Similarly, the construction of 2-methyldibenzo[f,h]cinnolin-3(2H)-one from 2-methyl-5-(2-bromophenyl)-6-phenylpyridazin-3(2H)-one and 2-methyl-5-(2-aminophenyl)-6-phenylpyridazin-3(2H)-one is also reported. Removal of the N-benzyl protective group of 2-benzyl-dibenzo[f,h]phthalazin-1(2H)-one with AlCl₃ yielded unsubstituted dibenzo[f,h]phthalazin-1(2H)-one.     

Twisted Diindeno-Fused Dibenzo[a,h]anthracene Derivatives and their Dianions

We report a facile synthesis of diindeno-fused dibenzo[a,h]anthracene derivatives ( DIDBA-2Cl , DIDBA-2Ph , and DIDBA-2H) with different degrees of non-planarity using three substituents (chloro, phenyl, and hydrogen) of various sizes. The planarization of their cores, as evidenced by the decreased end-to-end torsional angles, was confirmed by X-ray crystallography. Their enhanced energy gaps with twisting were investigated by a combination of spectroscopic and electrochemical methods with density functional theory, which showed a transition from singlet open-shell to closed-shell configuration. Moreover, their doubly reduced states, DIDBA-2Ph ²⁻ and DIDBA-2H ²⁻, were achieved by chemical reduction. The structures of dianions were identified by X-ray crystallographic analysis, which elucidated that the electron charging further distorted the backbones. The electronic structure of the dianions was demonstrated by experimental and theoretical approaches, suggesting decreased energy gaps with larger non-planarity, different from the neutral species.     

The synthesis of heterocyclic derivatives of dibenzo[a,d]cycloheptene

The synthesis of 2-amino-7,8-dihydrobenzo[1,2]cyclohepta[3,4,5-de]quinazoline ( 10 ) and 6,7-dihydrobenzo[1,2]cyclohepta[3,4,5-cd]indazole ( 5 ) is described.     

Facile synthesis of diiodinated dihydronaphthalenes and naphthalenes via iodine mediated electrophilic cyclization

A facile, efficient, and general synthetic method for a wide range of 2,3-diiodinated 1,4-dihydrothiophenes and naphthalenes has been developed via the electrophilic iodocyclization of various aryl propargyl alcohols. The resulting product 2p can be used for the synthesis of a rubrene intermediate.     

AuCl-catalyzed synthesis of benzyl-protected substituted phenols: a formal [3+3] approach

A AuCl-catalyzed synthesis of highly substituted, benzyl-protected phenols is developed. This reaction unites enal/enones and benzyl allenyl ether in a [3+3] fashion in two steps, allowing flexibility in phenol synthesis and excellent control of substitution at the benzene ring.     

New synthetic approaches to polycyclic aromatic hydrocarbons and their carcinogenic oxidized metabolites: derivatives of benzo[s]picene, benzo[rst]pentaphene, and dibenzo[b,def]chrysene

A new synthetic approach to polycyclic aromatic compounds is described that entails in the key steps double Suzuki coupling of PAH bisboronic acid derivatives with o-bromoaryl aldehydes to furnish aryl dialdehydes that are converted to larger polycyclic aromatic ring systems by either (a) conversion to diolefins by Wittig reaction followed by photocyclization or (b) reductive cyclization with triflic acid and 1,3-propanediol. This synthetic method provides convenient access to as many as three different polycyclic aromatic ring systems from a single Suzuki coupled intermediate. It was utilized to synthesize substituted derivatives of benzo[s]picene, benzo[rst]pentaphene, dibenzo[b,def]chrysene, and 13,14-dihydro-benz[g]indeno[2,1-a]fluorene, as well as the putative carcinogenic bisdihydrodiol metabolites of benzo[s]picene, benzo[rst]pentaphene, and dibenzo[b,def]chrysene.     

Diindeno-Fused Dibenzo[a,h]anthracene and Dibenzo[c,l]chrysene: Syntheses,Structural Analyses,and Properties

Diindeno-fused dibenzo[a,h]anthracene 6 and diindeno-fused dibenzo[c,l]chrysene 9 contain the key moieties 1,4-quinodipropene (1,4-QDP) and 2,6-naphthoquinodipropene (2,6-NQDP), respectively, and they both have an open-shell singlet ground state. The latter compound exhibits a strong biradical character and interesting properties, including a low ΔE_T−S (2.44 kcal mol⁻¹), a small HOMO–LUMO gap (1.06 eV), a wide photoabsorption range (250–1172 nm), and a large two-photon absorption cross-section (σ=1342±56 GM). This work verifies that 6 has a slightly larger HOMO–LUMO gap and ΔE_T−S than its helical isomer diindeno[2,1-f:1′,2′-j]picene (DIP), but is a much stronger two-photon absorber, verifying the important effect of geometry on the photophysical properties.     

The synthesis and X-Ray crystallographic analysis of a stable norbornadienone: 17-Oxo-7,16-methano-7,16-diphenylcyclopenta[d,e]tribenzo[a,h,j]anthracene

The reaction of 4,5-didehydroacenaphthene with phencyclone yields the title compound, a stable dibenzo-fused norbornadienone (8). The X-ray structure of8 is presented and compared with the structure predicted from a MM3, PM3, and a MMX calculation. Thermal decomposition of 8 produces, 7,16-diphenylcyclopenta[d,e]tribenzo[a,h,j]anthracene (9), a hydrocarbon that is computed to have a significantly twisted polycyclic aromatic skeleton with 19 kcal/mole of strain energy.     

First rational synthesis of dibenzo[fg,op]naphthacene discotics

A novel, versatile and regiospecific synthesis of variable degree substituted dibenzo[fg,op]naphthacene (also named dibenzopyrene) is described which involves the preparation of a tetraphenyl using a palladium-catalysed cross-coupling of arylboronic acids followed by photochemical cyclization.