A New Trifluoromethylating Agent: Synthesis of Polychlorinated (Trifluoromethyl)benzenes and 1,3-Bis(trifluoromethyl)benzenes and Conversion into Their Trichloromethyl Counterparts and Molecular Structure of Highly Strained Polychloro-m-xylenes

Article abstract of DOI:10.1021/jo00001a022

Mixtures of CCl3F and AlCl3 replace CF3 for H in polychlorobenzenes.Thus, by treatment of a solution of the suitable polychlorobenzene in CCl3F with AlCl3, the following compounds can be prepared: pentachloro- (2), 2,3,4,5-tetrachloro- (5), 2,3,4,6-tetrachloro- (8), 2,3,5,6-tetrachloro- (11), 2,3,4-trichloro- (14), 2,4,5-trichloro- (17), and 2,4,6-trichloro-1-(trifluoromethyl)benzene (20), as well as 4,5,6-trichloro- (31) and 2,4,6-trichloro-1,3-bis(trifluoromethyl)benzene (32).The reaction of the above-mentioned trifluoromethylated compounds with AlCl3 in CS2 yieldstheir trichloromethyl counterparts: 3, 6, 9, 12, 15, 18, 21, 34, and 36.The chlorination of 32 or 36 by means of Silberrad's reagent (SO2Cl2, AlCl3, and S2Cl2) affords perchloro-m-xylene (38), a new highly strained chlorocarbon whose synthesis was attempted repeatedly in the past. 9, 15, 17, and 21, when treated with oleum and then with water, are converted into 2,3,4,6-tetrachloro- (22), 2,3,4-trichloro- (23), 2,4,5-trichloro- (24), and 2,4,6-trichlorobenzoic acid (25), respectively; under similar treatment, 34, 36, and 38 give 4,5,6-trichloro- (33), 2,4,5-trichloro- (35), and tetrachloroisophthalic acid (39), respectively.The formation of the (trifluoromethyl)benzenes is discussed, and in this connection it has been found that CCl3F solutions of 3 and 18 in the presence of AlCl3 give back 2 and 17, respectively.Molecular structures of highly strained m-xylenes 36 and 38, as well as that of the much less strained 34, ascertained by X-ray analysis, are reported and commented.IR, UV, and NMR spectral data of the compounds synthesized are presented.The interesting UV spectrum of 21 is discussed.