CONFORMATIONAL ANALYSIS IN MULTISULFUR HETEROCYCLES .4. DUPLODITHIOACETONE AND 3,3 - 6,6-BIS(TETRAMETHYLENE)-S-TETRATHIANE

Variable-temperature nuclear magnetic resonance (nmr) spectroscopy has provided uniquely unequivocal evidence for a drastically lowered chair/twist energy difference in s-tetrathianes. The chair:twist ratio in solution is 1.0:2.6 for tetramethyl-s-tetrathiane (“duplodithioacetone”) at -15° and 4:1 for 3,3:6,6-bis(tetramethylene)-.s-tetrathiane at 0°. The barrier (ΔG‡) to chair/twist equilibration in s-tetrathianes is approximately 16 kcal/mole. A method for the preparation of the conformationally pure twist form of duplodithioacetone is described. A combination of the syn-axial and gem-dialkyl effects is proposed to account for the variation in the chair: twist ratio in a number of multisulfur heterocycles. © 1969, American Chemical Society. All rights reserved.