[4124-31-6] · C4Cl6O3 · Trichloroacetic Anhydride · (MW 308.74)
Alternate Name: TCAA.
Physical Data: mp -5 °C; bp 139-141 °C/60 mmHg; d 1.690 g cm-3.
Solubility: sol common organic solvents.
Form Supplied in: clear liquid, widely available.
Purification: distill in vacuo.
Handling, Storage, and Precautions: should be kept under inert gas; very reactive with water; corrosive.
The reactivity of trichloroacetic anhydride roughly parallels that of Trifluoroacetic Anhydride. For the formation of trichloroacetic esters and amides, Trichloroacetyl Chloride1 and hexachloroacetone2 are generally preferred to react with alcohol and amines, respectively.
A common use of TCAA has been its condensation with acylhydrazines, oximinoamides, or imidate esters to provide the corresponding five-membered trichloromethyl heterocycles (eq 1).3 The trichloromethyl group can then be displaced; for example, a 1,2,4-oxadiazole can be reacted with an appropriate nucleophile to provide the 5-amino compound (eq 2). A unique cyclization is the formation of a tetracyclic trichloromethyl amide diacetal (eq 3).4
Reaction of TCAA with trithioorthoacetates produces acylated vinyl sulfides in high yields (eq 4).5 Later results indicated that the reaction proceeds through a ketene dithioacetal6 and that the reaction may be extended to vinylketene dithioacetals (eqs 5 and 6)7 and other functional groups.8
Morimoto and Sekiya discovered that reactions of TCAA with Schiff bases and enamines provided an interesting array of heterocycles and chlorinated products (eqs 7-9).9
Patrick D. Lowder
Rhône-Poulenc Agricultural Products, Research Triangle Park, NC, USA