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DOI: 10.1055/s-2003-41414
Synthesis of Pyridinyl-Pyrimidines via Pd-Catalyzed Cross-Coupling Reactions: A Comparison of Classical Thermal and Microwave Assisted Reaction Conditions
Publication History
Publication Date:
28 August 2003 (online)
Abstract
The Negishi cross-coupling reaction was used for the synthesis of pyridinyl-pyrimidines utilizing classical thermal or microwave assisted conditions. The organozinc substrates were prepared from 2-fluoro-4-iodopyridine by conventional lithiation chemistry and subsequent transmetalation with ZnCl2 or ZnI2. Two different catalysts - Pd(PPh3)4 and Pd/C - were investigated for their ability to facilitate the cross coupling process with 2,4-dichloropyrimidine. We found that distribution and yield of desired compounds and possible by-products highly depend on the type of energy input. In contrast to thermal conditions, the microwave assisted method allowed efficient access to di-coupled compounds.
Keywords
palladium catalyzed cross-coupling reactions - Negishi-reaction, microwave assisted reactions - homogeneous catalysis - heterogeneous catalysis
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