Nitroacetic esters, alkylation

O-acetyl-jS-D-glycopyranosides from 0-, m- and p-02T C H 0 a-nitro esters from methyl nitroacetate, and alkyl phenyl selenides from PhSe". Similarly arenesulfonyl fluorides or isothiocyanates can be produced from arenesulfonyl chlorides and F" or SCN", and arene-carboxylic acid cyanides and isothiocyanates from arenecarboxylic acid chlorides and CN" or SCN ... 

Thus, the reaction of alkyl halides and a-halo esters with sodium nitrite provides a very useful synthetic method for nitroalkanes and a-nitro esters. However, ethyl bromoacetate is exceptional in that it fails to give ethyl nitroacetate on treatment with sodium nitrite.93 This is due to the acidic hydrogen of the ethyl nitroacetate, which undergoes a further reaction with sodium nitrite to give the oxidized products (see Section 6.1, which discusses the Nef reaction). In a similar way, the reaction of benzyl bromide with sodium nitrite at 25 °C gives benzoic acid predominantly. To get phenylnitromethane, the reaction must be carried out at low temperature (-16 °C) (Eq. 2.48).93... 

The general approach can be enlarged and conditions for condensation made milder by the use of further-activated esters, thus condensation with methyl nitroacetate produces 3-nitro-coumarins, condensations with Wittig ylides " allow orffto-hydroxyaryl ketones to be used ° and the use of diethyl malonate (or malonic acid ) (a 3-ester can be removed by hydrolysis and decarboxylation ), malononitrile, ethyl trifluo-roacetoacetate, or substituted acetonitriles in a Knoevenagel condensation, produces coumarins with a 3-ester, 3-trifluoroacetyl, " 3-cyano, or 3-alkyl or -aryl substituent. Condensation with IV-acetylglycine generates 3-acetylamino-coumarins. ... 

Carbon-Carbon Bond Formation. Direct coupling of an alcohol with a carbon acid by the use of DEAD/TPP has been limited to only a few examples because of the lack of carbon acids with pAa < 13. If enolizable carbonyl compounds are used, alkylation generally takes place on oxygen. Thus the reaction of 1,3-cyclohexanedione with isopropanol, DEAD, and TPP affords exclusively the O-alkylated product (eq 47). Cyanoacetate reacts at the carbon atom, while diethyl malonate is unreactive. However, the reaction of diethyl malonate with alcohols in the presence of ADDP and BU3P affords C-alkylated products in 3-56% yields (eq 48). Ethyl nitroacetate and nitromalonate oxidize the alcohol via an aci-nitro ester (eq 49). o-Nitroarylacetonitriles of general formula (50) undergo alkylation on carbon (eq 50). ... 

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