The conjugation of the benzene ring and the carbonyl group reduces the positivity of the carbonyl carbon, leading to a challenge to the subsequent attack of the nucleophilic group, and the final product yield is very low.
The conjugate effect of benzene ring and niobium-based reduces the positive electronity of carbon, which leads to the challenge of the follow-up attack of pro-nuclear group, and the yield of the final product is very low.
The conjugation of benzene ring with carbonyl group reduces the positive charge of carbonyl carbon, which leads to the challenge of subsequent attack of nucleophilic group, and the yield of final product is very low.<br>