Vapor phase alkylation of indole with methanol and dimethylcarbonate over Ni–Mn based ferrospinels

Vapor-phase methylation of indole with methanol and dimethylcarbonate (DMC) was carried out over Ni1−x MnxFe2O4 (x = 0, 0.25, 0.5, 0.75, 1.0) type ferrospinel in a fixed-bed reactor. 3-Methylindole was found to be the major product. It was observed that systems possessing higher ‘x’ values were highly selective for 3-methylindole. A maximum yield of 54.6% with selectivity 88.3% of 3-methylindole was obtained when methanol was used as alkylating agent, while yield of 48.6% with selectivity 80.1% was obtained using DMC as alkylating agent over MnFe2O4 under optimized conditions. Ni2+/Mn2+ ionic distribution in the spinel lattice influences the acido-basic properties. Effect of alkylating agent and different reaction parameters are discussed.