In the Miyaura-borylation reaction, the excess (BPin)2 was eluted along with product (aryl-boronic ester) due to close polarity [confirmed from 1H-NMR]. As (BPin)2 is invisible in the UV-light, it is impossible to locate it. Is there any way to remove it without destroying product (aryl-boronic ester)?
Dhirendra,
(BPin)2 can be visualized on TLC using gentle heating and Cerium/ Molybdenum based revealing reagents, it stains in very deep blue, time-wise much sooner (at a lower temperature) than the boronic ester. Also, column chromatography on Si-gel will frequently work well, depending on your scale.
Another thing is that if you do not use a large excess of (BPin)2, which normally you should not (we typically use 1.10-1.15 equiv), the next step typically goes well without a very careful removal of bispinacolatodiboron. After the coupling, chromatography - or oxidative workup with H2O2 if your scale is big - typically let you remove the remaining boron impurities.
Dhirendra, Generally use of 1.1 to 1.2 equivalent of bispinacolatodiboron in reaction doesn't require purification and after work up, you can use directly for next coupling reaction. (check whether your starting material is completely consumed).
After column purification wash the product with heptane you will get solid product.
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