Alkyl benzoylformates

Similar results are obtained on reduction of alkyl benzoylformates to alkyl (R)-man-delates (equation II). Again, the/-butyl ester is reduced with quantitative optical induction. 

The Norrish Type II behaviour of several alkyl benzoylformates (51) has been studied and shown to be the major triplet deactivation path for the photoexcited molecules. ... 

The result can be rationalized as follows the most important factor in the choice of the enantioface of carbonyl group in alkyl benzoylformate on which a hydride is transferred is the interaction between the alkoxycarbonyl group of the substrate and the amide side chain of the reductant mediated by Mg(II). 1,4-Dihydropyridine derivatives with symmetry have two polar amide side chains at the... 

McKenzie, A. CXXVII. — Studies in asymmetric synthesis. I. Reduction of menthyl benzoylformate. II. Action of magnesium alkyl haloids on menthyl benzoylformate. J. chem. Soc. [London] 85, 1249 (1904),... 

EE3.2. 2-keto esters. The Norrish-Yang reaction of 2-keto esters has been the subject of only a limited number of studies [19,20, 2Id,22]. Encinas and his coworkers investigated the photochemistry of some alkyl esters of benzoylformic acid [23a]. These aromatic 2-keto esters have a n,n absorption maxima >330 nm. Similar to aromatic monocarbonyl compounds all observed products originate from an excited triplet state. 

An analogous reaction of (86,RsMe or Et) with alkyl esters of benzoylformic acid (90ab) leads to (91ab) smd the same paper describes the reaction of (86) with... 

CATALYTIC ASYMMETRIC REDUCTION via HYDROSILYLATION OF ALKYL PYRUVATES AND ETHYL BENZOYLFORMATE [55]... 

Keto-esters.—Further examples of alkylations of the acyl anion equivalent (105) have been reported (c/. 2, 226 3, 16). Only in some cases can good yields of a-keto-ester dimethyl acetals be realized. In an extension of earlier work, N-aryl-triflamides have been found to be useful reagents for the overall oxidation of a-bromo-esters to a-keto-esters. Benzoylformates are accessible by carboxylation of anions derived from 2-aryl-l,3-dithians this approach seems to be an improvement on existing methods. 

The enzymes benzaldehyde lyase (BAL) and benzoylformate decarboxylase (BFD) have also been shown to catalyze enantioselective cross-benzoin reactions. Aryl-aryl as well as aryl-alkyl products are produced in high yield and enantiomeric purity. In the case of aryl-aryl products, the success of the reaction depends on the empirical identification of suitable donor/acceptor pairs. Aldehydes containing or/Ao-substituents were found to be ideal acceptors in BAL and BFD-catalyzed cross-benzoin reactions. The preparation of (/ )-l-(4-bromophenyl)-2-(2-chlorophenyl)-2-hydroxyethanone (25) from 4-bromobenzaldehyde (23) and 2-chlorobenzaldehyde (24) highlights the high conversion and selectivity possible in this transformation. As with rac-benzoin, rac-l-(4-bromo-phenyl)-2-(2-chlorophenyl)-2-hydroxyethanone is easily resolved by BAL to give the (5)-enantiomer with high enantiomeric purity. 

---