Bis(trifluormethylchalkogenyl)ketene (CF3E)2C = C = O (E = S, Se, SO2); Synthesen und Eigenschaften

Abstract

Bis(trifluoromethylchalcogenyl)ketenes (CF3E)2C = C = O (E = S, Se, SO2); Synthesis and PropertiesBis(trifluoromethylchalkogenyl)ketenes (1) are synthesized either by dehydrohalogenation of the corresponding acetyl chlorides or dehydratization of the corresponding acetic acids. In addition, treatment of trifluoromethylchalkogenyl chlorides with Ag2C = C = O provides 1 a in low but 1 b in good yields. Oxidation of bis(trifluoromethylsulfanyl)acetic acid with CrO3/H2SO4 gives some bis(trifluoromethylsulfonyl)ketene 1 c. Starting materials for the preparation of the ketenes are mono‐ and bis(trifluoromethylchalkogenyl)‐substituted orthoesters which are prepared from CH3C(OC2H5)3 and CF3ECl (E = S, Se). They are hydrolyzed to CH3‐n(ECF3)nC(O)OH (4). For E = Se the acids 4b,d are converted by SOCl2 into CH3‐n(SeCF3)nC(O)Cl (7a,b). Mono‐ and disubstituted malonic esters 5, 6 are formed by treating diethyl malonate with sodium and then CF3ECl. Acidic hydrolysis with 62% HBr converts 5 and 6 into the corresponding acetic acid derivatives 4. From CH3‐n(SCF3)nC(O)Cl and (CH3)3SiN3 isocyanate CH3‐n(SCF3)nNCO (n = 1, 2) are obtained in good yields. Hydrolysis of (CF3S)2C = C = O (1a) either in acidic or basic solution gives (CF3S)2CHC(O)OH (4c). Some chemical reactions of 1 a are described.