SELENOTHIOIC ACID S-ESTERS - SYNTHESIS, CHARACTERIZATION, AND TREND FOR STABILITY

Selenothioic acid S-alkyl esters were synthesized from the reaction of terminal acetylenes with n-butyllithium, selenium, and alkanethiols i n moderate to high yields. The use of substituted benzenethiols or (tr iphenylsilyl)-acetylene. allowed for the isolation of S-aryl esters, T he synthesis of alpha-aryl selenothioic acid S-alkyl esters was attain ed by the acid-catalyzed reaction of selenoacetic acid Se-alkynyl este rs with thiols in good yields. Se-77 NMR studies showed that the chemi cal shifts in a series of the esters were downfield of that in selenoe ster by about 500 ppm and were upfield of that in selenoketone by abou t 600 ppm, In the visible spectra the absorptions of the esters were o bserved at about 340 and 568 nm. X-ray molecular structure analyses of alpha-silyl esters showed that the bond distances in the selenocarbon yl group were 1.792 and 1.785 Angstrom, respectively, The formation of 1,3-diselenetane was confirmed from the decomposed products of S-phen yl ester. The trend for the stability of selenothioic acid S-esters is discussed on the basis of these synthetic results.