SYNTHESES AND CONFORMATIONS OF THE P-TERT-BUTYLCALIX[4] ARENETHIOLS

The reaction of dimethyl(thiocarbamoyl) chloride with p-tert-butylcali x[4]arene under various conditions yields mixtures from which most of the conformers of the mono-, bis-, tris-, and tetrakis(dimethyl(thioca rbamoyl))oxy compounds have been isolated and purified. Thermal rearra ngement of these compounds produces the (dimethylcarbamoyl)thio compou nds which, upon reduction with LiAlH4, afford the tetrathiol 14, the t rithiol 16, the 1,3-dithiol 21, and the monothiol24. X-ray crystallogr aphic structure determinations and variable-temperature H-1 NMR studie s show that the tetrathiol exists as an immobile 1,3-alternate conform er, the trithiol as a semimobile partial cone/1,3-alternate conformer, the 1,3-dithiol as a mobile flattened cone conformer; and the monothi ol as a mobile cone conformer. Although the tetrakis(( dimethylcarbamo yl)thio) compound exists in three noninterconverting forms comprising the 1,2-alternate 13, partial cone 18, and 1,3-alternate 19 conformers , all three yield the same tetrathiol 14 upon reduction. Similarly, th e syn 22 and anti 20 conformers of the 1,3-bis((dimethylcarbamoyl)thio ) compound yield the same dithiol 21. Molecular mechanics calculations for each of the conformers of the mono-, 1,3-di-, tri-, and tetrathio ls show general agreement with the X-ray data.