Synthesis and NMR spectroscopic studies of allylsulfanyl‐<b><i>N</i></b>¹‐alkyl‐<b><i>N</i></b>⁴‐phenyl‐1,4‐phenylenediamines and their cyclization products, 2,3‐dihydro‐1‐benzothiophenes and thiochromans

Abstract Regioselective addition of allylthiol at the C‐3 position adjacent to the nitrogen carrying the phenyl group of the 1,4‐phenylenediamine moiety of compounds 1 – 4 was rigorously confirmed by 1D NOE difference in combination with gHMBC experiments. The structures of 1,4‐phenylenediamines 1 – 4 , allylsulfanyl‐ N 1 ‐alkyl‐ N 4 ‐phenyl‐1,4‐phenylenediamines 5 – 8 and cyclization products 9 – 14 were completely analyzed in both CDCl 3 and DMSO‐ d 6 solutions. The 1 H and 13 C NMR spectra of 10 and 11, which contain two chiral centers, exhibit duplication for several signals, indicating the existence of two diastereomeric forms. The full structures of 5 and 9 were unambiguously confirmed by x‐ray crystallography. The 1 H and 13 C NMR spectra of all compounds were assigned using one‐ and two‐dimensional NMR techniques (APT, DEPT, 1D NOE difference, COSY, NOESY, HETCOR, gHMQC and gHMBC). Copyright © 2004 John Wiley &amp; Sons, Ltd.