Recently, we developed a rapid procedure for the Leuckart reaction and successfully applied it for the synthesis of substituted N-benzyl-N-methylformamides. Interestingly, in the reaction conducted on 4-phenylbenzaldehyde, a large amount of a by-product, N,N-di-(4-biphenylmethyl)-N-methylamine, was produced with an isolated yield of 41.2%. N-(4-biphenylmethyl)-N-methylformamide was produced as the main product with an isolated yield of 44.5%. We propose that due to the presence of a methyl group attached to the carbonyl, the reaction on 4-phenylacetophenone will proceed slower and produce a higher yield of N-[1-(4-biphenyl)ethyl]-N-methylformamide and a lower yield of N,N-di[1-(4-biphenyl)ethyl]-N-methylamine.  The reaction was conducted on a 10 mmol scale at 196-200°C. Column chromatography was used for the isolation of the products of the reaction. NMR-spectroscopy and elemental analysis were used to determine the structures of the products. The reaction was complete in 30 minutes compared to 10 minutes for the reaction with 4-phenylbenzaldehyde. The isolated yield of N-[1-(4-biphenyl)ethyl]-N-methylformamide was 88.5%. N,N-di[1-(4-biphenyl)ethyl]-N-methylamine was not isolated or detected.The results of the reaction support the initial hypothesis. The reaction provides a new method for the synthesis of N-[1-(4-biphenyl)ethyl]-N-methylformamide.

Synthesis of N-[1-(4-biphenyl)ethyl]-N-methylformamide

ACS Spring 2022

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