Creation of New Medicines Based on the Characteristic Reactivity of Allenes

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The allene bond of allene carbamate (1, 4-vinylidene-2-oxazolidinone) shows a chameleonic reactivity, changing the reaction patters widely depending on the kinds of its reaction partners. With terminal alkenes and alkynes, 1 undergoes [2+2]cycloaddition in a concerted manner and provides methylene cyclobutanes and methylenecyclobutenes. Respectively in good yields. The cycloaddition proceeds under strictly thermal activation conditions (70-100 ℃) with retention of the configuration of the alkene double bonds. Usually, [2+2]cycloaddition is a thermally forbidden process and the unique reactivity of 1 is explained on the basis of a [2π+2π+2π] Huckel transition state. With enols and allylsilanes, 1 undergoes unique 1,3-sulfonyl migration followed by the inverse electron demand Diels-Alder reaction giving rise to tetrehydropyridine derivatives. With silanes (RnSiH4-n, n = 1-3), alcohols, and thiols, 1 undergoes the 1,3-sulfonyl migration and provides a variety of 4-propylidene-2- oxazolidinones in excellent yields.