Dimethyl bromomalonate

Synthesis front Nitroso Compounds Aryl nitroso compounds (175) react easily with dimethyl bromomalonate in the presence of alkali to give the corresponding A-aryl-QC-dimethoxycarbonyl-nitrones (177) (Scheme 2.62) (333). 

In the presence of TMSC1, the organoindium reagent derived from indium and dimethyl bromomalonate adds to a wide range of conjugated enones under mild conditions in a 1,4-fashion, to yield oxo-1,3-diesters (Scheme 91).332... 

Bromination-dehydrobromination. Reaction of Red Salt (2) with dimethyl bromomalonate in CH,OH/NaOCH, produces 3 m 75-80% yield. Hydrolytic decarboxylation of 3 in refluxing aqueous HCI leads to bicyclo[3.3.0]octadiene-3,7-dione (4). 

With Mn(OAc)3, generated by oxidation of Mn(OAc)2 as mediator, a tandem reaction consisting of an intermolecular radical addition followed by an intramolecular electrophilic aromatic substitution can be accomplished [Eq. (21b)] [225b]. Further Mn(III)-mediated additions of 1,3-dicarbonyl compound to olefins are shown in Table 11 (numbers 8b,c, and 9a). Mediated by in situ generated Mn(III), methyl dibromoacetate, trichloro-bromomethane, perfluoroctyl iodide, dimethyl bromomalonate, and active methylene compounds have been added via radicals to olefins [225d]. 

In addition dimethyl allyl(bromo)malonate (4%) and dimethyl bromomalonate (35%) were formed. 

A French group have described the low-temperature dealkoxycarbonyla-tion of jS-ketoesters by boric anhydride, B2O3. A further example of thermal demethoxycarbonylation of substituted malonate esters has been reported halogen participation in charge dispersal has been invoked to account for the production of methyl bromoacetate from dimethyl bromomalonate (Scheme 26). 

The synthetic implications of this discovery were slow to be exploited. Base-initiated dimerizations of 2-cycloalkenones, known to give crystalline solids,3233 remained puzzling for some time before conjugate additions were suggested to account for some of the possible products 34 indeed, the product of base-catalyzed dimerization of 4,4-dimethyl-2-cyclopentenone, which proceeds via a double Michael addition sequence, was not identified until 1969 (Scheme 2).35 An unanticipated cyclopropanation reaction of acrylaldehyde36 37 using ethyl bromomalonate and proceeding by means of a similar Michael addi-tion-Sw enolate alkylation represents an early synthetic use of tandem vicinal difunctionalization. 

Electrophilic cyclopropanes 392, which are useful intermediates in organic syntheses, can be prepared by the cyclopropanation of olefins with diethyl dibromomalonate and its derivatives (81MI4). The reaction is carried out in the presence of 1 mol equiv. of copper(II) bromide and 2-4 mol equiv. of DBU. Alternatively, the reaction can be effected with diethyl bromomalonate (83BCJ2687) in the presence of a catalytic amount of copper(II) bromide and a slight excess of DBU in benzene at ambient temperature. When some other base (e.g., triethylamine, DABCO, pyridine, or sodium hydride) was applied instead of DBU, the yield was lower or no reaction occurred. The use of other copper salts led to a decrease in the yield. When cyclopropanation was carried out in dimethyl sulfoxide, dimethylformamide, or acetonitrile, the yield of product 392 was again lower. 

Recently, Ferroud et al. [154] found another dye sensitizer. Rose Bengal, highly effective as a visible light photoredox catalyst in the direct enantioselective a-alkylation of aldehydes with stabilized dimethyl 2-bromomalonate (132) (Scheme 8.40). The reaction proceeded smoothly under visible light irradiation at room temperature and with short reaction times when co-catalyst (LiCl) was used, providing a-alkylated aldehydes in high yields (up to quantitative yield) with high enantioselectivity (up to 85% ee). 

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