Acid hydrolysis Sommelet reaction

Selective o/t/io-acylation and orrfio-formylation of 2-alkyl pyridines is possible by [2,3] sigmatropic rearrangement (Sommelet-Hauser) of a-pyrrolidinyl-2-alkylpyridine sulfonates (268), prepared by treating the parent base with cyanomethyl benzenesulfonate (76JOC2658). Acid hydrolysis of the rearranged product (269 R = H) yields 3-formyl-2-methylpyridine (270). Methylation of (269 R = H) using NaH-Mel and acid hydrolysis of the reaction mixture gives 3-acetyl-2-methylpyridine (270 R = Me). 

The Delepine reaction or the Del6pine amine synthesis is the closest variation of the Sommelet reaction. The Delepine amine synthesis is the acid hydrolysis of the hexaminium salt 2 with strong acid in ethanol, giving rise to benzylamine 4 with the formaldehyde being removed as volatile formaldehyde diacetal.13-15 In essence, it may be considered as half of the Sommelet reaction or the interrupted Sommelet reaction. The Delepine reaction works well for active halides such as benzyl, ally halides, and a-halo-ketones. 

A modern adaptation uses trifluoroacetic acid as catalyst. That allows for formylation of aromatics such as toluene and xylene and even electron deficient phenols such as 2,4-difluorophenol under mild conditions in good yields.A high order of para regioselectivity is exhibited even for phenols.The mechanism involves fast aminomethylation followed by a rate-determining dehydrogenation step to the imine similar to that observed in the Sommelet reaction hydrolysis then gives the aldehyde (Eq 1.42). ... 

Ethoxyacetic acid was first prepared by Heintz by the reaction of chloroacetic acid with sodium ethylate. The procedme described above is essentially that of Sommelet. Ethoxyacetic acid has also been prepared by hydrolysis of ethoxyacetonitrile with concentrated hydrochloric acid and by the action of excess sodium ethylate on 1,1,1,2-tetrachlorethane and on a,/3-dichloro-vinyl ethyl ether. A recent patent reports a synthesis from diethyl ether and carbon dioxide at high pressure. 

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