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Methods for the Synthesis of Heteroaryl-substituted 1,4-Benzo- and 1,4-Naphthoquinones. (Review)

“…A limitation of this method is the fact that the reaction only takes place successfully if one of the nucleophilic centers is a sulfur (or selenium) atom, which as a rule carries out the initial attack at the electrophilic center of C-Cl. In some cases after nucleophilic substitution the formation of a tricyclic condensed benzo[b]furan derivative, resulting from ring closure by intramolecular substitution of the hydroxy group, was observed instead of cyclization [79][80][81][82].…”

“…The reaction of benzo[b]furan 73 with potassium O-butyl xanthate [81], triethylammonium N-methyl-or N-phenyl dithiocarbamates [92], and the N,N-dialkylhydrazinium salts of the N,N-dialkylhydrazides of dithiocarbonic acid [82] leads to substitution of the chlorine atom at position 3 and the formation of the corresponding derivatives 82 and 83. When heated in the presence of concentrated sulfuric acid or hydrochloric acid, the products undergo recyclization with the formation of a 1,3-dithiol-2-one [81] or thiazoline-2-thione [82,92] The reaction of benzo[b]furan 73 with dithiooxamide (rubeanic acid) in acetic acid gave 2,2'-bi[5-(2,5-dihydroxy-3,4,6-trichlorophenyl)thiazole] 86, which is readily oxidized to the quinone (87) [93,94].…”

“…When heated in the presence of concentrated sulfuric acid or hydrochloric acid, the products undergo recyclization with the formation of a 1,3-dithiol-2-one [81] or thiazoline-2-thione [82,92] The reaction of benzo[b]furan 73 with dithiooxamide (rubeanic acid) in acetic acid gave 2,2'-bi[5-(2,5-dihydroxy-3,4,6-trichlorophenyl)thiazole] 86, which is readily oxidized to the quinone (87) [93,94]. A side product of the reaction of benzo[b]furan 73 with rubeanic acid is 2-imino-3,4-dihydro-4H-1,4-thiazine-3-thione 88, which is also oxidized to the quinone 89.…”