Reaction of Hexachlorobenzene and (Pentachlorophenyl)lithium with α-Arylacetonitriles

Article abstract of DOI:10.1021/jo00112a019

(Pentachlorophenyl)lithium (2) reacts with α-lithio-α-arylacetonitriles (4) at -70 deg C to room temperature to supply α-aryl-α-(2,3,5,6-tetrachlorophenyl)acetonitriles 7.Small amounts of 1,2,4,5-tetrachlorobenzene (8) and trans-1,2-dicyano-1,2-diarylethylenes 9 are also obtained; however, no α-tetrachloroarylated nitriles 6 from 3,4,5,6-terachlorobenzyne were detected.Similar treatment of hexachlorobenzene (1) and 4 afforded α-aryl-α-(2,3,4,5,6-pentachlorophenyl)acetonitriles 10.The addition of 2 to 4 at tetrachlorobenzyne-generating temperatures (0-20 deg C) gave a complex mixture containing mainly dimeric and polymeric materials; 6 was not found.A mechanism is proposed for the reaction of 2 and 4 which suggests that nitriles 7 are formed by the condensation of 2 and 4 via a four-centered transition state and that alkenes 9 are supplied by a base-mediated dimerization of α-chloro-α-arylacetonitriles 13, formed by a lithium-chlorine exchange between 2 and 4.Nitriles 10 most likely are provided from the reaction of 1 and 4 by the usual aromatic nucleophilic substitution pathway.