Methyl Benzoylformate

The benzene contains 80 g. of impure ethyl benzoate boiling at 180-260° and containing about 20 per cent of ethyl benzoylformate. In the case of the methyl ester the benzene contains 60 g. of impure methyl benzoate, boiling at 170-250°, and containing about 20 per cent of methyl benzoylformate. 

Reductions of keto esters to esters are not very frequent. Both Clemmensen and Wolff-Kizhner reductions can hardly be used. The best way is desulfurization of thioketals with Raney nickel (p. 130). Thus ethyl acetoacetate was reduced to ethyl butyrate in 70% yield, methyl benzoylformate (phenylglyoxy-late) to methyl phenylacetate in 79% yield, and other keto esters gave equally high yields (74-77%) [82J]. 

Pyrrolopyridine derivatives, such as compound 144, in the presence of Mg salts such as magnesium perchlorate, serve as chiral and nonchiral NADH models in the reduction of organic nitro compounds <1996JHC1211>. Similar derivatives, such as compound 145, serve as NADH models in the asymmetric reduction of methyl benzoylformate and A -acetyl enamines <1997TA3309>. 

Methyl benzoylformate [15206-55-0] M 164.2, m 246-248°. Purified by radial chromatography (ethyl ether/hexane, 1 1), and dried at 110-112° at 6mm pressure. [Meyers and Oppenlaender JACS 108 1989 1986. ... 

Keto Esters Asymmetric transfer hydrogenation of functionalized ketones is rare. However, an excellent optical yield is obtainable inreduction of methyl benzoylformate by using 2-propanol and with a catalyst system consisting of [RhCl(C6H]0)]2, (S,S)-DMDPEN, and KOH (Scheme 1.89) [313],... 

The photolysis of hexachloroacetone or tribromoacetaldehyde in methanol does not yield any alcoholysis product253. The major reaction is reduction. On the other hand, a,a,a-tribromoacetophenone yields the alcoholysis product methyl benzoylformate in good yield (equation 56)254. The initial photomethanolysis product is a,a-dibromo-a-methoxy-acetophenone, which in a dark reaction is converted into the benzoylformate. The methyl benzoate is formed by nucleophilic attack on the carbonyl carbon. 

The resulting dihydroquinoline 7 turned out to be an enantioselective reducing agent, since it transformed methyl benzoylformate to methyl-(5)-mandelate with 99 % ee. This reaction is... 

Heterogeneous catalytic hydrogenation of the methyl esters of a-keto acids over modified metal catalysts other than nickel have been studied using a cinchonidine-modified platinum catalyst. " Methyl pyruvate and methyl benzoylformate were hydrogenated to form methyl (R)-lactate and (R)-mandelate with high ee (81-84%). 

Fig. 21.3 The effect of pore size and confinement in the asymmetric hydrogenation of methyl benzoylformate to methyl mandelate after 120 min of reaction...

In contrast to asymmetric hydrogenation, examples of stereoselective reduction of functionalized ketones are rare. Scheme 43 illustrates the highly enantioselec-tive reduction of methyl benzoylformate in 2-propanol containing KOH using a catalyst prepared in situ from [RhCl(CgHjo)]2 and (S,S)-3 [101]. With the same catalyst, methyl pyruvate is reduced in 5% optical yield. 

Alkenes. Alk-3-en-l-ynes are obtain in the presence of SnC and (PhiPl.PdCl.-carboxylic acids are degraded by one cartx Reductive silylation. a-Diketoncs i while methyl benzoylformate undergoei 2,3-diphenyl-2,3-bis(( -trimethylsilyl)tartn (Me,P)2PdCl2]. 

Reductive silylation. a-Diketones are converted into l,2-(bissiloxy)ethenes, while methyl benzoylformate undergoes reductive coupling to give dimethyl 2,3-diphenyl-2,3-bis(0-trimethylsilyl)tartrate with McjSiSiMej [catalyzed by (MeiPljPdClj],... 

As noted in the introduction to this section, under UV light irradiation, carbonyl groups [42] and alkenes [43] will add photochemically in a 2 + 2 sense across the 2- and 3-positions of indole, but only if an acyl or aroyl group is present on the indole nitrogen atom. The photocycloaddition reaction of carbonyl compounds with acylindoles was first reported by Julian and Tringham in 1973 [42], They found that irradiation of N-acetylindole or N-para-chlorobenzoylindole with benzophenone, benzoyl-formamide, or methyl benzoylformate gave oxetane products, as shown in Scheme 12. The stereochemistry of the products was not reported. No products were obtained when the indoles were irradiated with acetophenone, benzaldehyde, acetone, or propionaldehyde. This observation... 

The viologen reduction by EDTA in reverse micelles in the presence of Ru(bpy)3 is another example of vectorial photoinduced electron transfer [106], The accumulation of photoproducts is associated with the catalytic cycles depicted in Fig. 10(b). The oxidative quenching of the ruthenium complex occurs at the micelle outer boundary, while the regeneration of the dye takes place by the oxidation of EDTA in the inner core of the micelle. The reduction of the final product 4-dimethylaminoazobenzene is further mediated by the acceptor 1-benzylnicotinamide (BNA ). In Fig. 10(c), the photocatalytic reduction of methyl benzoylformate (MBF) by thiosulfate is described in the presence of the porphyrin ZnTPPS and the mediator quinolinium-3-carboxiamide (DCA ) [107]. This sequence of reactions occurs only in micelles such as those formed by hexadecyl-trimethylammonium bromide, which contain in the interior the ultimate donor acceptor. Finder illumination, ZnTPPS photoreduces DCA to DCQ, which is subsequently extracted into the micelle core. Within the microenvironment, DCA is regenerated via reduction of MBF, while the oxidized porphyrin is reduced by thiosulfate outside the micelle. 

Fuji et al. separated the atropisomers of 277 on Chiralcel OD-H at the preparative scale. CD spectra were recorded but the absolute configuration was not established. Reduction of each atropisomers afforded axially chiral NAD(P)H models that were engaged in the enantioselective reduction of methyl benzoylformate (95% ee) (92JCS(CC)905). 

For hydrogenation of both p3Tuvates and MeBf (methyl benzoylformate) Modification of Pt-alumina catalysts with Cn, Qn, or Qnd was less effective than modification with Cnd. Modifying with Cnd and Qn resulted in the (S)-(+) isomer of MeLa rather then the (/ )-(-) isomer as in the case of modifying with Cn. This indicated that the absolute configuration of the resulting hydroxy ester is determined by the configurations at the C and Cg centers in the alkaloid moleeules (see Seheme 5.6.). 

Table 5.12. Asymmetric hydrogenation of methyl benzoylformate into...

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