ORGN 529 |
| The transition metal catalyzed cyclization of alkynoic acids represents an efficient synthesis of enol lactones. Such densely functionalized small heterocycles are of high interest because they serve as versatile intermediates in the synthesis of pharmaceuticals and natural products. While investigating the Cu(I)-catalyzed cycloaddition of N(alpha)-protected L-propargylglycine (1) and azides, we observed that the expected triazole products were formed in considerably lower yields compared to related “click reactions”. Examination of the reaction mixtures revealed the formation of a side product, enol lactone 2. The same heterocycle is obtained as the sole product in high yields in the absence of azides. The Cu(I)-catalyzed transformation of alkynoic acids to enol lactones at room temperature in water is an economically and ecologically attractive alternative to reported syntheses, which require elevated temperature, organic solvents, and costly catalysts (e.g. Pd, Rh). Several examples of the cyclization of alkynoic acids in water will be presented.
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Physical Organic Chemistry, Metal-Mediated Reactions, Asymmetric Reactions and Syntheses
8:00 PM-10:00 PM, Tuesday, August 21, 2007 BCEC -- Exhibit Hall - B2, Poster
Division of Organic Chemistry |
