Stereoselective synthesis and stereochemistry of r-2-alkoxycarbonyl-c-3-o-substituted phenyl-1,4-thiazane 1,1-dioxides

Abstract

r-2-Alkoxycarbonyl-c-3-aryl-1,4-thiazane 1,1-dioxides were obtained as the stereoselective product, when the aldehyde used was o-substituted benzaldehyde while the p-substituted benzaldehydes gave a trans product. The relative configuration of the adjacent alkoxycarbonyl and aryl groups was assigned from the vicinal coupling constant, 3J = 10.6 Hz in the trans isomer and 3.2 Hz in the cis isomer, and from the multiplicity pattern, i.e., a doublet for the H-2 proton of the trans isomer and a triplet for the H-2 proton of the cis isomer. The unusual, large long-range coupling (4J = 2.8 Hz) because of the "W" arrangement between H-2e and H-6e across the ring type was very useful for confirming the cis configuration and chair conformation of the isomer. The various 1H and 13C NMR assignments were made with the help of 1H–1H COSY, 1H–13C COSY, HMBC, and NOESY spectral analyses.Key words: 1H and 13C NMR, 1H–1H COSY, 1H–13C COSY, HMBC, NOESY, stereoselectivity, 1,4-thiazane.