Synthesis and alkylation of triethylammonium 3,5,5-tricyano-4,6-di(2-thienyl)-1,4,5,6-tetrahydro-pyridine-2-selenolate

Abstract

Partially hydrogenated pyridines with selenium substituents form a small class of organic compounds [1,2]. In the course of our study of cyanoselenoacetamide derivatives [3][4][5], we have developed a method for the synthesis of a new selenium heterocyclic system, namely, triethylammonium 3,5,5-tri-cyano-4,6-di(2-thienyl)-1,4,5,6-tetrahydropyridine-2-selenolate (1). 2-Cyano-2-(2-thienyl)methylideneselenoacetamide (2) [6, 7] was found to react with (2-thienyl)methylidenemalononitrile (3) in the presence of excess triethylamine to give 1,4,5,6-tetrahydropyridine-2-selenolate 1 in 71% yield. This selenolate obtained is readily alkylated by bromide 4 at the selenium atom to give 2-aroylmethylselanyl-1,4,5,6-tetrahydropyridine 5 in 62% yield. N H Se S S CN NC NC N H Se S S O NC NC CN Me S Se NH 2 CN S CN CN Et 3 N, Br O Me Et 3 NH 1 5 2 + 3-4°C EtOH,  + 4 3 Me 2 COThe IR spectra were obtained on an IKS-29 spectrophotometer for samples in vaseline mull. The 1 H NMR spectra were taken on a Bruker Avance II 400 spectrometer at 400 MHz in DMSO-d 6 with TMS as internal standard. The elemental analysis was carried out on a Perkin-Elmer C,H,N-analyzer. The purity of the compounds obtained was monitored by thin-layer chromatography on Silufol UV-254 plates with 1:1 acetonehexane as the eluent with development by iodine vapor and a UV detector. The melting points were determined on a Koffler block and not corrected.