3,4,5,6-Tetrachloro-l,2-benzoquinone

With chlorinated quinones. New heterocycles containing 1,2-dihydro-imidazo [l,2- ]imidazol-3-one 405 or 1/7-imi-dazo[l,2- ]pyrazole moieties were obtained via charge-transfer interaction of creatinine or 3-aminopyrazole with some 7i-deficient compounds such as 2,3-dichloro-5,6-dicyano-l,4-benzoquinone, 2,3,5,6-tetrachloro-l,4-benzoquinone, 2,3-dichloro- or 2,3-dicyano-1,4-naphthoquinone, and 3,4,5,6-tetrachloro-l,2-benzoquinone (Equation 183) C1996BSB159, 2001HC0541, 2000PS1>. 

Triazido 6 chloro l 4( ) benzoquinone,0 C6-C1(N3)3 0 mw 265.59, N 47.48% red-violet cryst, mp-expl on heating diffc sol in glac AcOH, but not decompd by boiling in glac AcOH was prepd by treating 2,3,5,6-tetrachloro-l,4-benzoquinone (Chloranil) with an excess of Na azide in boiling ale... 

Monocyclic azines are very weak --donors and behave mainly as n-donors on interaction with electrophiles. However, 7r-donor character is significantly increased in their benzo derivatives which have higher energy HOMOs (Table 2). For example, acridine 25 forms a highly colored 1 1 molecular complex with 2,3,5,6-tetrachloro-l,4-benzoquinone (chlor-anil). Perimidine 96 is one of the strongest heterocyclic --donors and gives deeply colored molecular complexes with a variety of organic electron acceptors. This is consistent with its electron-rich structure and its separate classification. 

ReCle] " is photooxidized by electron acceptors, for example, 2,3,5,6-tetrachloro-l,4-benzoquinone (chloraml) and DDQ, to [ReCle], which is an intermediate in the oxidation of Cl to CI2 and of toluene to benzaldehyde. ... 

The elements sulfur and selenium, which combine with the hydrogen evolved to give, respectively, H2S and H2Se. Little is known about this mechanism either. Quinones, which become reduced to the corresponding hydroquinones. Two important quinones often used for aromatizations are chloranil (2,3,5,6-tetrachloro-l,4-benzoquinone) and DDQ (2,3-dichloro-5,6-dicyano-l,4-ben-zoquinone). The latter is more reactive and can be used in cases where the substrate is difficult to dehydrogenate. It is likely that the mechanism involves a transfer of hydride to the quinone oxygen, followed by the transfer of a proton to the phenolate ion ... 

For example, the dianil of Pigment Violet 37 (S, B = D = OCH2CH3, A = NHCOPh, E = H, X = NHCOCH3) is formed by the reaction of 2,5-diethoxy-4-ben-zoylaminoanUine (6), (B = D = OCH2CH3, A = NHCOPh) with 2,5-diacetylamino-3,6-dichloro-l,4-benzoquinone (7), (X = NHCOCH3). Similarly the reaction between 3-amino-9-ethylcarbazole (9) and 2,3,5,6-tetrachloro-l,4-benzoquinone (10) affords the dianil precursor of Pigment Violet 23 (S), where A and E correspond to the fused indole moiety and B = D = H,X = C1. 

Tetraazido-l,4-benzoquinone can be easily prepared by the action over several hours of sodium azide on 2,3,5,6-tetrachloro-l,4-benzoquinone p-chloranil) in an ethanol suspension [165] or by the action of aqueous sodium azide on a methylene chloride solution of p-chloranil [166]. 

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