2-thiophen-2-yl-ethylamine

In one route, tidopidine (1) was assembled via Sn2 displacement of 2-chlorobenzyl chloride (9) with 4,5,6,7-tetrahydro-thieno[3,2-c]pyridine (8). " The nucleophile 8 was synthesized by heating 2-thiophen-2-yl-ethylamine (6) with 1,3-dioxolane in the presence of concentrated hydrochloric acid. 1,3-Dioxolone gave better yields than with formaldehyde, paraformaldehyde and 1,3,5-ttioxane. The interesting transformation 6 —> 8 first involved the formation of the corresponding Mannich base 7, which then underwent a Pictet-Spengler type reaction to afford the ring-closure product 8. It was of interest to note that a possible intramolecular aminomethylation did not take place. 

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