Background: 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-chlorobenzaldehyde, a large amount of a by-product, N,N-di-(2,4-dichlorobenzyl)-N-methylamine, was produced with an isolated yield of 31.3%. N-(2,4-dichlorobenzyl)-N-methylformamide was produced as the main product with an isolated yield of 52.0%. Hypothesis: Due to the presence of a methyl group attached to the carbonyl, the reaction on 4-chloroacetophenone will proceed slower and produce a higher yield of N-[1-(4-chlorophenyl)ethyl]-N-methylformamide and a lower yield of N,N-di-[1-(4-chlorphenyl)ethyl]-N-methylamine. Methods: The reaction was conducted on a 10 mmol scale at 185-187°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. Results: The reaction was complete in 40 minutes compared to 10 minutes for the reaction with 4-chlorobenzaldehyde. The isolated yield of N-[1-(4-chlorophenyl)ethyl]-N-methylformamide was 88.5%. N,N-di-[1-(4-chlorphenyl)ethyl]-N-methylamine was not isolated or detected. Conclusions: The results of the reaction support the initial hypothesis. The reaction provides a new method for the synthesis of N-[1-(4-chlorophenyl)ethyl]-N-methylformamide.

Rapid synthesis of N-[1-(4-chlorophenyl)ethyl]-N-methylformamide

ACS Spring 2022

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