Dimerisation, of methyl acrylate

The dimerisation of methyl acrylate is an important reaction since the product, dimethyl dihydromuconate, represents a useful precursor for speciality chemicals such as cyclopentenones, as well as for the production of nylon-6,6. The synthetic challenge is to avoid formation of head-to-tail dimerisation products. The tail-to-tail dimerisation of methyl acrylate with palladium catalysts has been evaluated in protic and common imidazolium ionic liquids.17 21"231... 

Scheme 8.5 Tail-to-tail dimerisation of methyl acrylate...

Tail-to-tail dimerisation of methyl acrylate has been investigated with a rhodium catalyst in protic and neutral imidazolium ionic liquids.171 While acidic ionic liquids showed some advantage with palladium catalysts (vide supra), reaction rates with Rh(Cp )(C2H4)2 as catalyst were much lower in [HC4im][BF4] and [HCiim][BF4] relative to those in [C4Ciim][BF4], It was suggested that this was due to coordination of imidazole to the rhodium centre. 

Head-to-tail dimerisation of methyl acrylate to the dimethyl ester of 2-methylenepentane-dioic acid (126) occurred in 82-85% yield in the presence of catalytic amounts of P(RNCH2CH2)3N with R = PP, Bu or Bz but the less sterically hindered proazaphosphatrane with R = Me, gave oligomer or pol-ymer. The proazaphosphatrane, P(RNCH2CH2)3N with R = Bu also acts as an effective ligand for the palladium-catalyzed direct arylation of ethyl cyano-acetate (127) with aryl bromides (e.g. 128) to form (129) in high yield. ... 

Head-to-tail dimerisation of methyl acrylate to the dimethyl ester of 2-methylenepentane-dioic acid (126) occurred in 82-85% yield in the presence of... 

Acenaphthylene forms [2 + 2]-cycloaddition products with electron-deficient alkenes such as acrylonitrile and methyl acrylate (Nakamura et al., 1978). Cycloaddition is favoured by carrying out the reaction in a micellar solution owing to the inefficiency of the dimerisation in such an organised system. 

Acrylonitrile and methyl acrylate can be dimerised to afford trans - 1,2-cyclobutanes using (ethylene) bis -(triphenylphosphine) nickel or bis -(triphenylphoephine) nickelacyclopentane as the catalysts.Photodimerization of the coloured styrylpyrylium salts (176) and (177) in the crystalline state has been reported. ... 

The dimerlsatlon of methyl methacrylate and the codimerlsatlon with methyl acrylate in the presence of a catalyst derived from PdCl 2(MCPh)2 + 3AgBF, Is likely to Involve u-allyl Pd(IV) hydride Intermediates. If the dimerlsatlon Is carried out under D2, deuterium is incorporated in the product.The dimerisation of methacrylate by Ru catalysts gives a mixture of products (eq.l4). The structure of one Ru complex formed In this reaction (39) has been determined.Treatment of (C6H6)Ru(maleic anhydride)2 with two equivalents NaCjoHs gives a superior methacrylate dimerlsatlon catalyst whose activity Is Increased in polar sol vents. 

The continuous and batch microwave reactors have been particularly useful for heating reactions in which thermally labile products are formed. For example, alkyl 2-(hydroxymethyl)acrylates have considerable potential as functionalised monomers and synthons128. Published syntheses at ambient temperature, however, required several days and were not conducive to scale-up129-133. The microwave procedure involved a modified Baylis-Hillman reaction, in which the parent acrylate derivative was reacted with formalin in the presence of 1,4-diazabicyclo [2.2.2] octane (DABCO). Preparations from starting acrylates, including methyl, ethyl and n-butyl esters, were easily achieved within minutes with multiple passes through the CMR, at ca. 160-180°C (Scheme 9.16). Rapid cooling was required to limit hydrolysis, dimerisation and polymerisation. Yields... 

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