Quinoxalin-2-ones chlorination

QuinoxaIin-2-oncs are readily converted into the corresponding 2-chloroquinoxalines by treatment with phosphoryl chloride in the case of the highly insoluble 2,3-diones chlorination is effected conveniently with a mixture of phosphoryl chloride and dimethyl-aniline. The use of phosphorus pcntachloride may lead to side reactions, for example, quinoxalin-2-one (70) is converted into 2,3-... 

Electrophilic substitution of quinoxaline-2,3-dione and its 1,4-dimethyl derivative occxu at positions 6 and 7. For example, treatment of a solution of quinoxaline-2,3-dione in concentrated sulfuric acid with one equivalent of potassium nitrate yields the 6-nitro derivative, whereas with two equivalents of potassium nitrate 6,7-dinitroquinoxaline-2,3-dione is formed. 6-Bromo and 6,7-dibromoquinoxaline-2,3-dione have been prepared by bromination of the 2,3-dione in sulfuric acid with bromine and silver sulfate, and chlorination is found to occur under similar conditions. Treatment of quinoxaline-2,3-dione with fuming sulfuric acid yields the... 

Chloroquinoxalines are usually prepared by chlorination of quinoxalin-2-ones. Reagents that have been employed for chlorination include phosphoryl chloride, mixtures of phosphoryl chloride and phosphorus pentachloride, and phosphoryl chloride and pyridine. The reaction is normally uncomplicated by side reactions, but the use of phosphorus pentachloride alone as the chlorinating reagent is best avoided... 

The Diels-Alder reaction of meso-tetraarylporphyrins with the pyrazine o-quinodimethane mainly affords the oxidized 49a-c instead of the expected chlorin adducts. The bisaddition is site specific, occurring in opposite pyr-rolic rings and leads to 51 and 52. The novel polycyclic 50a-c, 52a, and 52b result from the coupling between the P-fused quinoxaline ring and one adjacent meso-aryl group. In contrast to compounds 49a and 51a, there... 

The use of the palladium-copper catalyst enables the cyclization of compound 125d under milder conditions, which leads to the retention of the chlorine atom in the molecule. Owing to the presence of aryl iodides (bromides) in the reaction mixture, quinoxaline 125d converts into 1-benzyl-substituted imidazo[l,2-a]quinoxalines 127a-g in one-pot process. The use of iodine analogs instead of bromonitroben-zenes allows one to increase the yield of compounds 127a, b by 20 % (Bakherad et al. 2012). 

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