Design of Boradecarboxylation Reaction

2020-01-22T07:00:32Z (GMT) by Yuji Naruse Atsushi Takamori Kenji Oda
For mechanism of decarboxylation reaction, all textbooks show that the electron moves from the piC=O bond. However, the most donating bond orbital in the carbonyl group should be the lone pair(s) on the oxygen. Thus, a picture of orbital theory with delocalization from a lone pair should be more appropriate than that from the piC=O orbital. We confirmed our idea by theoretical calculation. In the TS, if we use 2-substituted b-ketoacids, the boat-form conformation should result in exclusively preferred generation of E-enolates. Normally, decarboxylation reaction performs in polar solvent, so that the resulting enols should be transformed to the corresponding ketones by tautomerization. Suppose we use the heteroatoms to obtain the enolate or enol ethers without tautomerization, it would offer a diastereoselective enol(ate) synthesis with regioselectivity, since the C=C double bond should always be introduced between two carbonyl groups. After screening the heteroatoms by the theoretical calculations, we found that boron is suitable for this purpose. We confirmed our idea by theoretical calculations, offering a new boradecarboxylation reaction to produce enolates diastereoselecitively and regioselectively.