Six-membered Systems with More than One Heteroatom

Six-membered Systems with More than One Heteroatom 

N-aryl-2-piperazmones are of great interest as famesyl-transferase inhibitors, and both N-aryl-2-piperazinones and N-aryl-2,5-piperazinediones are synthetic precursors of N-arylpiperazines which are key elements in monoamine receptor-active drugs. Lange et al. enhanced the Goldberg reaction with microwaves for synthesis of N-arylpiperazinones, N-arylpiperazinediones, and N-aryl-3,4-dihydroquinolines [88]. Microwave irradiation greatly accelerates the reaction when NMP is used as solvent. 

Yeh and Sun have combined the advantages of microwave technology with liquid phase combinatorial chemistry to facilitate the synthesis of thioxotetrahydropyrimi-dinones [90]. The reactions were significantly accelerated. 

90% yield (33% using conventional heating, 40 °C, 24 h, for the first step) 

Hydroxymethylation of uracil, 5-hydroxymethyl-2, 3 -0-isopropylideneuridine, 5 -0-tert-butyldiphenylsilyl-2, 3 -0-isopropylideneuridine, 2, 3 -0-isopropylidenecy-tidine, and 2, 3 -0-isopropylidene-5 -0-tritylcytidine was efficiently achieved in very high yields by El Ashry and coworkers with paraformaldehyde in alkaline medium under the action of microwave irradiation [92]. 

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Six-membered Systems with More than One Heteroatom 10.3.5.1 Synthesis of Pyrimidines and Related Compounds... 

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