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The highly reactive 1:1 intermediate produced in the reaction between tert-butyl isocyanide and dialkyl acetylenedicarboxylates is trapped by dialkyl 2-bromomalonates to yield the title compounds in fairly high yields.2H-Pyran-2-one and its derivatives are important starting materials in the synthesis of cyclobutadienes. 1Y2 These heterocycles ¢nd use in cycloaddition reactions, providing bicyclolactone adducts which can be elaborated into a variety of highly functionalized cyclohexadienes and benzenes. 3À5 Current synthetic methodology for preparation of this class of compounds still remains fairly speci¢c. 6Y7 Here, a direct, e¤cient and operationally convenient approach to the synthesis of highly functionalized 2H-pyran-2-one derivatives 3 using dialkyl 2-bromomalonates 2 is presented. Thus, reaction of tert-butyl isocyanide with dialkyl acetylenedicarboxylates 1 in the presence of a strong CH-acid such as 2 leads to the corresponding 2H-pyran-2-one derivatives 3 (Scheme 1).The three-component condensation reactions produce the hitherto unknown functionalized 2H-pyran-2-ones 3 in high yields. The structures of the isolated crystalline compounds 3a ^d were deduced from elemental analyses, 1 H and 13 C NMR spectroscopy. IR spectroscopy was applied to distinguish 3 from the primary product, ketenimine 5 (Scheme 2), which apparently undergoes further transformations to produce the 2H-pyran-2-one ring system under the given reaction conditions. Thus, the IR spectra of the isolated products showed strong NH stretching bands at ca. 3225^3210 cm À1 for alkylamino groups. Further evidence was obtained from proton couple 13 C NMR spectra which showed no methine carbon resonance.

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