Trichloromethyl ketones, reduction

Carbon tetrachloride undergoes stepwise reduction at mercury in DMF containing TEABr [45]. Several groups of workers [46-52] have electrogenerated the shortlived trichloromethyl anion, which can react with acrylonitrile, ethyl acrylate, diethyl fumarate, alkyl monohalides, and a variety of aldehydes and ketones. De Angelis and coworkers [53] have used dichlorocarbene, generated via reduction of carbon tetra-... 

The catalytic reduction of trifluoromethyl ketones was successfully realized by using catecholborane as reductant. In the case of the reduction of anthryl trifluoromethyl ketone, one recrystallization of the crude (i )-alcohol (94% ee) afforded the enantiopure carbinol [35]. Trichloromethyl ketones were also reduced... 

The expected reactions of the cyano group attached to triazine ring carbon with amine, alcohol, and azide nucleophiles have been described <90NKK396>. Reduction of ketone to alcohol with sodium borohydride <88HCA712> and trichloromethyl groups to methyls with lithium aluminum hydride are also reported <86MI 6l2-02>. 

Enantioselective reduction of trichloromethyl ketones/ These ketones arc reduced by catecholborane (CB) in the presence of 0.1 equiv. of the chiral oxazaborolidine 1 to trichloromethylcarbinols 2 in 92-98% cc. These products are useful in themselves,... 

Hydrodehalogenation. A synthesis of chiral epoxides from trichloromethyl ketones is through enantioselective reduction to the trichloromethyl carbinols and tinhydride-mediated conversion to the chlorohydrins before base treatment to close the three-membered ring. Dehalogenation of halocarboxylic acids in water is apparently a method that deserves wide application. 

Enantioselective synthesis of a-amino acids A practical and general route to a-amino acids involves enantioselective reduction of alkyl trichloromethyl ketones with catecholborane (CB) in the presence of the oxazaborolidine (S)-l (0.1 equiv.) to give (R)-alcohols 2. The (R)-alcohols (2) are converted on treatment with NaOH... 

This reaction was first reported by Corey and T.ink in 1992. It is an enantioselective synthesis of a -amino acids by means of the asymmetric reduction of trichloromethyl ketones from catechoiborane in the presence of either (/ )- or (5)-oxazaborolidine, followed by the treatment of the resulting alcohols with base and sodium azide and subsequently the reductive conversion of the azido group into an amino group. Therefore, this reaction is generally known as the Corey-Link reaction. Occasionally, it is also referred to as the Corey-Link amino acid synthesis, Corey-Link procedure, etc. 

Shono T, Ohmizu H, Kawakami S, Nakano S, Kise N (1981) Electroorganic chemistry. 47. A novel chain reaction induced by cathodic reduction. Additirai of trichloromethyl anion to aldehydes or vinyl acetate. Tetrahedron Lett 22 871-874 Shono T, Kise N, Yamazaki A, Ohmizu H (1982) Electroorganic chemistry. 61. Novel selective synthesis of ot-chloromethyl, a, a-dichloromethyl, and a, a, a-trichloromethyl ketones from aldehyde utilizing electroreduction as key reaction. Tetrahedron Lett 23 1609-1612... 

Scheme 12.60. The trichloromethyl ketone is reduced with catecholborane in the presence of the (5 )-oxazaborohdine catalyst. The resulting (i )-secondary alcohol (produced in high enantioselectivity) is treated with sodium hydroxide and sodium azide to yield the corresponding (5 )-a-azido carboxylic acid, and reduction then produces the amino acid (after Corey, E. J. Link, J. O. /. Am.Chem.Soc., 1992,114,1906).

The enantioselective reduction of trichloromethyl ketones to corresponding alcohols is catalysed by the Ru complex (58) in the presence of Et3N and HCOOH under N2. The product alcohols react in a range of Jocic-type reactions to give enantiomerically enriched amino-amides. ... 

Shimizu et al. have reported the synthesis of the 4-hydroxy-6-lactone component of mevinic acid by lactonization of a 6-hydroxy ester [53] (Scheme 16). Reaction of lithio-fcrt-butylacetate with p-trichloromethyl-p-lactone 80 gave 6-hydroxy-p-keto ester 81. A stereoselective syn reduction of the ketone, lactcmization, and protection of the secOTidaiy alcohol provided the lactone. The trichloromethyl group was reduced with tri- -butyltin hydride to furnish 6-chloromethyl lactone intermediate 84. 

---