3- Methylenecyclopentanecarboxylic acid derivs

Whereas palladium(0)-catalyzed reactions of dialkyl fumarate and dialkyl maleate yield reaction products identical to those obtained from the phosphane-modified nickel-catalyzed reactions (vide supra), analogous palladium(0)-catalyzed reactions with ( )-but-2-enoic or (E)-cinnamic acid derivatives lead to different products to the nickel-catalyzed reactions, i.e. in the palladium-catalyzed reactions formal distal cleavage of but-2-enoic MCP occurs to provide methyl tra i-2-methyl-4-methylenecyclopentanecarboxylate (12, R = Me) and methyl trans-4-methylene-2-phenylcyclopentanecarboxylate (12, R = Ph), respectively." Yields and stereoselectivities are slightly higher with palladium(O) catalysts. When R = Me, 7.4% of the C-C double bond isomerization product, methyl traM -2,4-dimethylcyclopent-3-enecarboxylate (13, R = Me), is additionally obtained, raising the combined yield of cyclocodimers to 49.9%. With methyl (jE )-cinnamate, analogous isomerization only occurs upon workup, i.e. distillation of the crude product. 

The nickel(0)-catalyzed codimerizations of methylenecyclopropane (26) or 2,2-dimethylmethylene-cyclopropane with the chiral derivatives of acrylic acid lead to optically active 3-methylenecyclopen-tanecarboxylic esters or amides (39 equation 16) in good yields (Table 3). When (-)-camphorsultam acrylate is used, 3-methylenecyclopentanecarboxylic amides are obtained in up to 98% de. °... 

Vinyl carbanions derived from acrylic esters and their jS-phenyl derivatives react with several carbon electrophiles to give a-substituted and a,/8-disub-stituted derivatives. While /8>alkyl substituted acrylates have been shown to dimerize in the presence of potassium catalyst at 110 C. Three simple unsaturated esters undergo palladium(0)-catalysed codimerization with methylenecyc-lopropane to furnish methylenecyclopentanecarboxylic esters in reasonable yield. An efficient procedure for the oxidation of isatins to anthranilic acid esters has appeared. Methyl 2,4,6-tri-isopropylbenzoate forms a dipole-stabilized carbanion on reaction with Bu Li, which then reacts with carbon electrophiles [e.g. E = Bui, (CH3)2C0, or CH3CHO] to give a range of ester derivatives in good yield (Scheme 52). ... 

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