Predict the major product of the following reaction :
MH SET - 2025, SET Exam - 2025,
Answer: A
The product is methyl 6-(p-tolyl)nicotinate, option A.
Pd(dha)2 with the ligand dPPf catalyses a Kumada cross-coupling: Pd(0) inserts into the activated C-Cl bond next to the ring nitrogen, the Grignard reagent transmetallates, and reductive elimination joins the two aryl groups. At -40°C the catalyst reacts with the aryl chloride much faster than the Grignard reagent attacks the ester, so the CO2Me group survives.
B and D are what an uncatalysed or warm Grignard reaction with the ester would give (ketone, then tertiary alcohol after a second addition), and they still contain the coupling product. C is the homocoupling product of the Grignard reagent, 4,4'-dimethylbiphenyl, which is only a minor side product under catalysis.
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