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The carbonyl group behaves as a heterodienophile towards simple dienes. Curtius degradation of the gem-diester to carbonyl completes a synthesis of ?-unsaturated δ-lactones: Rocz. Chem., 38, 707 (1964); J. Am. Chem. Soc., 97, 6892 (1975); J. Org. Chem., 42, 4095 (1977):
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Undergoes the Baylis-Hillman reaction in which a carbanionic species, generated by the reversible addition of 1,4-Diazabicyclo[2.2.2]octane, A14003, to a Michael acceptor, adds to the carbonyl group: Synth. Commun., 19, 2461 (1989).• For asymmetric Diels-Alder reaction, see: J. Chem. Soc., Chem. Commun., 676 (1987). For addition to aza-dienes, see: Tetrahedron Lett, 30, 2685 (1989).
• Thus, the reagent could be regarded as a CO2 equivalent in both the above sequences.
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Ene-addition to alkenes occurs at the less-substituted carbon. Oxidative degradation leads to ?-unsaturated carboxylic acids: J. Am. Chem. Soc., 102, 2473 (1980); 106, 3797 (1984):
• Reacts with activated arenes under Friedel-Crafts conditions, or with aryllithium or Grignard derivatives, to give aryl hydroxymalonates, hydrolysis and decarboxylation of which gives substituted mandelic acids: Org. Synth. Coll., 3, 326 (1955). Alternatively, they may be transformed reductively to arylmalonates and hence to ester enolates: J. Org. Chem., 47, 4692 (1982).
