ORGN 403 |
| Pyrrole derivatives represent a class of compounds of great importance in heterocyclic chemistry primarily due to the fact that many pyrroles are subunits of natural products, pharmaceutical agents and polymers. The valuable and diverse biological properties of pyrroles make the development of efficient methods for the preparation of these compounds, having a defined substitution pattern, a focus of considerable synthetic effort. A stereoselective approach to the synthesis of indolizidine alkaloids, based on the reaction of pyrrole derivatives of amino acids has been reported. The Paal-Knorr synthesis, starting from primary amines and 1,4-dicarbonyl compounds and their masked equivalents such as tetrahydro-2,5-dimethoxyfuran, is often used for the construction of pyrrole rings. Although there are quite a number of methods available for the synthesis of pyrroles, most of them involve multi-step synthetic operations which lower the overall yield and there are limited reports on the preparation of enantiomers of pyrrole derivatives having 1-N directly linked to the stereogenic center.The development of a flexible and selective method to obtain pyrroles with a variety of substituents are desirable. In this work, we have designed a convenient route to 1,2-, 1,2,3-, 1,2,4-, and 1,2,3,5- substituted pyrrole rings from amines, amino alcohols and amino acids with simple accessible chloroenones. A series of substituted pyrroles has been synthesized in high yields on treatment of chiral primary amines, amino alcohols and esters of a-amino acids with chloroenones, functionalized dicarbonyl compounds in organic solvents or under microwave conditions without solvents. The conversions work without racemization. |
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Process R&D, Practical Synthesis, and Methodology
1:00 PM-4:20 PM, Tuesday, 15 March 2005 Convention Center -- Room 11A, Oral
Division of Organic Chemistry |