Pergamon Tetrahedron Letters, Vol. 38, No. 51, pp. 8829-8832, 1997 O 1997 Elsevier Science Ltd All rights reserved. Printed in Great Britain 0040-4039/97 $17.00 + 0.00 PII: S0040-4039(97) 10383-5 PREPARATION OF DITHIOSELENIDES V/A A SELENIUM TRANSFER REAGENT M. Dominic RyanI and David N. Harpp* Department of Chemistry, McGill University Montreal, QuebeG Canada H3A 2K6 Abstract: The addition of two moles of th/ol to a unique selenium-transfer reagent, bis azole selenide 4, results in very good isolated yields of dithioselenldes (RS-Se-SR). © 1997Elsevier ScienceLtd. Selenium is essential in living systems; it is believed to be transported/n vivo as a dithioselenide of glutatnione or eysteine or coenzyme-A.2 More recently, Block and Uden3 have discovered this class in low concentration in garlic; the positive effects of selenium even in these small amounts in the diet, is of considerable interest. The only synthetic preparation of bis(alkylthio)selenldes (1) reported to date is that shown in Eq. (1). 2c The r,,echanism of this reaction has been examined. 4 4R-SH + H2SeO3 .m> R.S.Se-S.R + R-S-S-R + 3H20 (Eq. 1) 1 Although this method gives moderate yields of two variants of 1, the dithioselenides are strongly contaminated (ca. 30-65%) with a variety of other products which are hard to remove; the disulfide and thiosutfonate (RSO2SR) are the major impurities. Because sulfur transfer reagents have had a long and successful history,5 we sought to develop a selenium analogue to facilitate the preparation of dithioselenides and related compounds. There have been a number of reports of useful selenium reagents in the literature; 6 N-pbenylselenosuccinlmide 2 and N- phenylselenophthalimide 3 have been prepared previously from two routes. We published the first preparation of a bis-azole selenide 47 and now wish to report its ability to serve as a selenium transfer reagent. The preparation of reagent 4 was carried out as follows.8 Two equiv, of N-chloro-benzotriazole were dissolved in 1 mL of dry CH2CI2 under an argon atmosphere and cooled to -20 oC, whereupon the solute precipitate. One equiv, of diallyl selenide 7a in 1 mL of CHeCI2 was added dropwise via a syringe. The solution became homogeneous. This was allowed to warm to rt over 1 h, and a white precipitate was formed. The reaction mixture was stirred for 16 h and was triturated with 2 x 5 mL of dry bexanes with stirring. The 8829