17839-53-1Relevant articles and documents
Conformational Behaviour of Medium-sized Rings. Part 10. Dithiosalicylides and Trithiosalicylides
Guise, G. Bruce,Ollis, W. David,Peacock, Judith A.,Stephanatou, Julia Stephanidou,Stoddart, J. Fraser
, p. 1637 - 1648 (2007/10/02)
The trithiosalicylide derivatives (8)-(11) have been synthesised and shown by temperature-dependent 1H n.m.r. spectroscopy to exist in solution as ring inverting (35a)(35b) enantiomeric helical conformations with trans-thioester linkages.The free energies of activation for these conformational changes are ca. 10 kcal mol-1 higher than those for the similar process in the corresponding trisalicylides.In contrast with the trisalicylides, the trithiosalicylides can only ring invert between enantiomeric helical conformations via intermediates containing a cis-thioester linkage.The dithiosalicylide derivatives (3)-(7) have been synthesised; the temperature dependence of the 1H n.m.r. spectrum of di-o-thiothymotide (7) has been interpreted in terms of ring inversion (40a)(40b) between enantiomeric boat conformations.Comparison of the ΔG value of 24.6 kcal mol-1 for this conformational change with that of 17.7 kcal mol-1 previously obtained for di-o-thymotide (41) suggests that cis-thioester linkages are subject to more resonance stabilisation than are cis-ester linkages.
