Synthesis and NMR spectroscopic studies of Allylsulfanyl-N1-alkyl-N4-phenyl-1,4-phenylenediamines and their Cyclization Products, 2,3-Dihydro-1-benzothiophenes and Thiochromans
Regioselective addition of allylmercaptan at the C-3 position adjacent to the nitrogen carrying phenyl group of the 1,4-phenylenediamine moiety of 1−4 was rigorously confirmed by the 1D NOE difference in combination with gHMBC experiments. The structures of 1,4-phenylenediamines 1−4, allylsulfanyl-N1-alkyl-N4-phenyl-1,4- phenylenediamines 5−8, and cyclization products 9−14 were completely analyzed in both CDCl3 and DMSO-d6 solutions. The 1H and 13C NMR spectra of 10 and 11 containing 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 1H and 13C 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).