Allenes and alkynes are among the most important building blocks in organic synthesis. We have been defining the reactivity of a new class of nitrogen-substituted allenes and alkynes, specifically allenamides and ynamides, in which the nitrogen atom contains an electron-withdrawing group. These allenamides and ynamides possess much needed stability compared to classical nitrogen-substituted allenes and alkynes. However, more significantly, their unique conformational rigidity and attractive coordination ability have allowed us to develop highly stereoselective synthetic methods. Therefore, it is the goal of this NIH proposal to explore applications of these stereoselective methodologies. For chemistry of ynamides in Aim-l, we propose en-ynamide ring-closing metathesis to construct complex nitrogen heterocycles. For chemistry of allenamides, we propose in Aim-2 a total synthesis of (+)-zincophorin, featuring the application of a hetero [4 + 2] cycloaddition.
In Aim -3 and Aim-4, we propose total syntheses of (-)-1-isothiocyanate-aromadendrane, (+)-parvineostemonine, and (+)-Iyconadin A, featuring applications of N-substituted oxyallyl cation intramolecular [4 + 3] cycloadditions. These synthetic applications can demonstrate the potential of allenamides and ynamides in constructing complex natural products. Investigations proposed here should continue to revitalize interest in the chemistry of allenamines and ynamines which show great promise in organic synthesis.
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