S-Functionalization of 3,5-bis(2-pyridyl)-1,2,4,6-thiatriazine: probing the effect of alkyl chain length in the development of tethered materials

Abstract

Reactions between 3,5-bis(2-pyridyl)-4-hydro-1,2,4,6-thiatriazine (Py₂TTAH) and a series of 1,n-dibromoalkanes (n = 2, 3, 4, 5, 6, 8, 10) were explored and a synthetic route to prepare tethered 3,5-bis-(2-pyridyl)-1λ⁴,2,4,6-thiatriazines is described. When the length of the alkyl group employed is n ≥ 4, S,S′-alkyl-bis(Py₂TTA) derivatives (8–12) are isolated; however, if n < 4, S-cyclopropyl-Py₂TTA (13; n = 3) and S-ethenyl-Py₂TTA (14; n = 2) are formed due to competitive intramolecular S_N2 cyclization and E2 reactions, respectively. NMR spectroscopy, electron spray ionization mass spectrometry and X-ray crystallography were used to probe the dependence of the alkyl chain length on the reaction pathway. Computational studies are also presented, which support the preference of intramolecular vs. intermolecular S_N2 reactions when n = 3 and n > 3, respectively.