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[摘要]：The deproto-metalation reactions of pyrimidine and pyrazine were regioselectively carried out using Li tris(2,2,6,6-tetramethylpiperidino)cadmate in THF at room temp. This result was demonstrated by subsequent trapping with I2 to afford 4-iodopyrimidine and -pyrazine in 71 and 63% yield, resp. The same reaction performed on pyridazine afforded a mixt. of the corresponding 3- and 4-iodo deriv. (55 and 41% yield, resp.). From pyrazine, access to the 2,5-diiodo deriv. (40% yield on 25 mmol scale) proved possible using a larger amt. of base (1 instead 1/3 equiv). |
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