Journal ArticleDOI
Conformational behaviour of medium-sized rings. Part 10. Dithiosalicylides and trithiosalicylides
G. Bruce Guise,W. David Ollis,Judith A. Peacock,Julia Stephanidou Stephanatou,J. Fraser Stoddart +4 more
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TLDR
The trithiosalicylide derivatives (8, 11, and 12) have been synthesized and shown by temperature-dependent 1H n.m.r. spectroscopy to exist in solution as ring inverting enantiomeric helical conformations with trans-thioester linkages as discussed by the authors, and the free energies of activation for these conformational changes are ca. 10 kcal mol-1 higher than those for the corresponding trisalicylides.Abstract:
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.read more
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Book ChapterDOI
Synthesis of Thioesters and Thiolactones
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