[76-02-8] · C2Cl4O · Trichloroacetyl Chloride · (MW 181.82)
(acylation of amines to give trichloroacetamides;1 undergoes Friedel-Crafts type acylations as an alkyl choroformate equivalent;2 convenient precursor of dichloroketene;3 acylates enol ethers;4 reacts with organozinc reagents to generate trichloromethyl ketones5)
Physical Data: mp -146 °C; bp 114-116 °C; d 1.629 g cm-3
Solubility: sol ether, THF, dichloromethane, benzene, toluene.
Form Supplied in: colorless oil.
Analysis of Reagent Purity: commercial reagent is 99% pure.
Preparative Method: can be generated by action of Phosphorus Oxychloride on Trichloroacetic Acid.
Purification: distillation with the rigorous exclusion of moisture.
Handling, Storage, and Precautions: reagent is highly toxic and should be handled with gloves.
Amines can be readily converted into the corresponding trichloroacetamides with trichloroacetyl chloride and Triethylamine (eq 1).6 Dehydration of amides can be performed in a similar fashion, which allows mild access to the corresponding nitriles (eq 2).7 Allylic trichloroacetamides can also be used to generate aminochlorohydrins (eq 3).8
Trichloroacetyl chloride undergoes facile addition to heterocycles in a Friedel-Crafts fashion (eq 4).9 Given the ability of these products to undergo haloform-type reactions, this allows access to aryl acids, esters, and amides (eq 5).10,11
Dehalogenation of trichloroacetyl chloride with activated Zinc yields a solution of dichloroketene (eq 6).3
Trichloroacetyl chloride adds to enol ethers and thioenol ethers in a regiospecific fashion, and these adducts undergo elimination to generate a,b-unsaturated ketones (eq 7).12,13
Addition of trichloroacetyl chloride to an organozinc reagent proceeds without catalyst to give trichloromethyl ketones (eq 8).5 These can be reduced enantioselectively and therefore serve as a source of asymmetric a-hydroxy and a-amino acids14
James W. Leahy
University of California, Berkeley, CA, USA