Trichloroacetyl chloride, from

Triaryl phosphite-ozone adducts, 706 Tri( -butyl)silyl peroxides, bis(trimethylsilyl) peroxide reactions, 796 Trichloroacetyl chloride, from tetrachloroethene, 731... 

Trichloroacetanilide has been prepared from hexachloroacetone and aniline, from trichloroacetyl chloride and aniline, by the action of aniline magnesium iodide on ethyl trichloroacetate, by heating N-phenyltrichloroacetimidyl chloride with dilute methanol, and from trichloroacetic acid and aniline in the presence of phosphorus oxychloride. ... 

In the reaction with enamino ketones derived from dimedone (e.g., 49) p-toluenesulfonyl chloride gives the chloroiminium cation (138) isolated as the perchlorate. This indicates that initial O sulfonation is followed by addition of chloride ion and subsequent expulsion of tosylate (42) in a manner similar to the trichloroacetyl chloride reaction with 49 (Section IV.A). 

Acylation of the vinylogous pyrrolidine amide of dimedone with acetic anhydride or acetyl chloride led (possibly indirectly) to the carbon acylation product, whereas trichloroacetyl chloride gave rise to products derived from attack of chloride at the oxygenated double bond position in an initial 0-acylation product (401-404). 

Symmetrical piperazines 364 have been obtained from the corresponding 4,5-dihydrazinofurazano[3,4- ]pyraz ne 363 in good yield on reaction with acetic anhydride in the presence of a Lewis acid (Equation 98) <1999CHE499>. When formaldehyde was used, the yield was slightly reduced at 76%. Acid chlorides can also be used in this reaction although the yield drops to 23% when trichloroacetyl chloride is used. 

Trichloroacetyl chloride was purchased from Fluka Chemical Corporation and distilled before use. 

Methyl-1-cyclopentene (96% pure) and trichloroacetyl chloride (99% pure) were purchased from the Aldrich Chemical Company, Inc. The trichloroacetyl chloride was distilled prior to use. 

Methods of acylating pyrrole similar to the present one have been reported using oxalyl chloride,5 trifluoroacetic anhydride,6 carbamic acid chloride,7 and trichloroacetyl chloride.8 In the last preparation, it was necessary to separate the product from highly colored by-products by alumina chromatography. Pyrrol-2-yl trichloromethyl ketone has also been prepared by the interaction of pyrrolylmagnesium halide and trichloroacetyl chloride.9... 

The allylthioether (1.5 mmol) and about 15 mmol of Zn/Cu alloy were placed in vigorously stirred ether (15 ml) under argon and the mixture was heated to reflux. A solution of freshly distilled trichloroacetyl chloride (3 mmol) in ether (5 ml) was added dropwise to the solution over 4h by means of a syringe pump. After cooling, the reaction solution was decanted from the residue and the thioester purified by chromatography on silica gel (87%), syn structure, d.e. >94%. 

Trichloroacetyl chloride (obtained from Fluka Chemical Corporation) was distilled immediately before use. 

Attempts to add dichloroketene to 3//-pyrrolizine (1) were largely unsuccessful, giving Friedel-Crafts products (Section III,B,4) but in one case, in which the ketene was generated from trichloroacetyl chloride and activated zinc in ether, an adduct (294) (or its regioisomer) was obtained.123 The double bond in the 1 H-pyrrolizin-1 -one can act as a dienophile with cyclopentadiene ester 295 was isolated.26... 

A second example of this type of elimination is the generation of dichloroketene from trichloroacetyl chloride and zinc ... 

Figure 15.33 is based on the first and most common method for the preparation of dichloroketene, i.e., the reductive /3-elimination of chlorine from trichloroacetyl chloride with zinc (for the mechanism see Sections 4.7.1 and 17.4.1). Upon addition of the dichloroketene to the isomerically pure 2-butenes perfect stereoselectivity (and hence overall stereospecificity) occurs /ra .v-2-butene reacts to give frans-dichlorodimethylcyclobutanone and cis-2-butene to furnish its cw-isomer. 

Fig. 15.33. Prototypical in situ generation of dichloroketene through reductive -elimination of chlorine from trichloroacetyl chloride. Stereospecific [2+2]-cycloaddi-tions of this dichloroketene with the stereoisomeric 2-butenes.

Figure 12.32 shows the second commonly employed method for the generation of dichloroketene, which involves the reductive / -elimination of chlorine from trichloroacetyl chloride by zinc (cf. Sections 4.7.1 and 14.4.1 for mechanistic considerations). The addition of the dichloroketene to the trisubstituted alkene A (Figure 12.32) exhibits ori-... 

Fig. 12.32. Orientation-selective and diastereoselective [2+2]-cycloaddition with in situ generated dichloroketene II the dichloroketene is generated by way of a reductive /3-elimination of chlorine from trichloroacetyl chloride.

Acylations of enaminones is a well known process1. However, the reaction of trichloroacetyl chloride interestingly differs from the normal reaction of acyl halides in yielding pyrans by attack of the a-methyl group of enaminone (equation 38)56. This gives a new access to cyclic and acyclic compounds by using various transformations. 

Double bonds adjacent to complexed dienes can be cyclopropanated using diazomethane, methyl diazoacetate, or sulfur-based ylids. Cycloheptatriene iron tricarbonyl undergo a [2 -F 2] cycloaddition with chloroketene derived from trichloroacetyl chloride (Scheme 161). 

Cyeloaddition to silyl enol ethers. As expected, dichloroketene, generated from trichloroacetyl chloride and activated zinc, reacts with silyl enol ethers to form 3-silyloxy-2,2-dichlorocyclobutanones, usually in good yield. Cycloaddition does not obtain with dichloroketene generated from dichloroacetyl chloride and triethylamine. In some cases only acyclic products are formed, but these may arise by ring opening of intermediate cyclobutanones. ... 

Cycloaddition to alkynes. Dichlorokelene, generated from trichloroacetyl chloride by zinc (8,156), adds to alkynes to give cyclobutenones. The reaction occurs preferentially with the triple bond of enynes. 

A mixture of 41 g. (0.25 mole) of trichloroacetic acid and 53 g. (0.375 mole) of benzoyl chloride is placed imder an efficient fractionating column and heated. The trichloroacetyl chloride is removed from the top of the column as rapidly as it is formed. The head temperature should not be allowed to go above 119°. The distillate is redistilled through the same column. During the first part of the distillation, a high reflux ratio should be maintained, since in this way hydrogen chloride present in the material from the first distillate is eliminated. There is obtained 23 g. (51%) of trichloroacetyl chloride boiling at 116-119° at atmospheric pressure. 

Carbon tetrachloride could be formed by the abstraction of a chlorine atom from a hexachloroacetone molecule by a trichloromethyl radical tetrachloroethylene could then result from the dimerisation of dichlorocarbene radicals produced from the dissociation of pentachloroacetonyl radicals. Haszeldine and Nyman identified trichloroacetyl chloride and octachloropropane as products of the liquid phase photolysis, suggesting a primary step of Type 3 involving rupture of the carbon-halogen bond. Photolysis in the liquid phase was found to be very slow, and this has been attributed to cage effects and recombination of radicals formed in the primary step. 

The Staudinger ketene cycloaddition was utilized as the key reaction in the synthesis of a number of bakkane natural products in the laboratory of A.E. Greene. Dichloroketene was generated in situ from trichloroacetyl chloride by zinc-copper alloy in the presence of phosphorous oxychloride. The [2+2] cycloaddition between dichloroketene and 1,6-dimethylcyclohexene gave the product in high yield and excellent regio- and diastereoselectivity. The cycloadduct was successfully converted to (+)-bakkenolide A. 

A variety of cydopropanecarbonitriles have been prepared by dehydration of cyclopropanecarboxamides. The reactions were with phosphorus pentoxide and triethylamine, ° phosphoryl chloride, thionyl chloride/ and trichloroacetyl chloride and triethylamine. The yields ranged from mediocre to very good, an example is dehydration of carboxamide 1 to carbonitrile 2. ... 

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