Selective synthesis of allenyl aryl tellurides from diaryl ditellurides and propargyl bromide

Abstract

Unsaturated tellurides are widely used in organic synthesis as intermediate products and synthons [1]. Cross coupling of vinyl tellurides underlay stereoselective syntheses of functionalized alkenes [1]. Development of new efficient procedures for the preparation of unsaturated tellurides containing both double [2, 3] and triple bond [4] from acetylene derivatives and nucleophilic [2] or electrophilic [3, 4] tellurium-containing reagents constitutes a line of our studies. Allenyl aryl selenides are generally prepared by isomerization of propargyl selenides under basic conditions [5]. Only a few data are available on the synthesis of allenyl aryl tellurides. Pourcelot [6] reported on the reaction of phenylchalcogenolate anions with propargyl bromide, which led to the formation of propargyl phenyl chalcogenides or mixtures of propargyl phenyl chalcogenides and allenyl phenyl chalcogenides. Following this procedure, allenyl phenyl telluride was synthesized in 27% yield. We have developed an efficient procedure for the synthesis of allenyl phenyl telluride (I) and previously unknown allenyl 4-tolyl telluride (II) in 90–93% yield from diaryl ditellurides and propargyl bromide (Scheme 1). The reaction was highly selective, and no aryl propargyl telluride was detected. Sodium tetrahydridoborate was gradually added to a solution of propargyl bromide and diaryl ditelluride in methanol at room temperature. The reduction of diaryl ditelluride with NaBH4 generates arenetellurolate anion which replaces the halogen atom in propargyl bromide. The reaction of diphenyl diselenide with propargyl bromide under analogous conditions gave 95% of phenyl propargyl selenide with high selectivity, while allenyl phenyl selenide was not detected. The spectral parameters of phenyl propargyl selenide were consistent with published data [5]. Selective formation of allenyl aryl tellurides indicates that the reaction follows 1,3-nucleophilic substitution pattern rather than usual 1,1-nucleophilic substitution that could lead to propargyl tellurides. Presumably, attack by bulky highly nucleophilic arenetellurolate anions on the terminal carbon atom at the triple bond is more favorable than on the carbon atom attached to halogen. In the former case, nucleophilic attack is accompanied by shift of electron density with simultaneous formation of allenyl fragment and bromide ion. ISSN 1070-4280, Russian Journal of Organic Chemistry, 2012, Vol. 48, No. 12, pp. 1569–1570. © Pleiades Publishing, Ltd., 2012. Original Russian Text © M.V. Musalova, M.V. Musalov, V.A. Potapov, S.V. Amosova, 2012, published in Zhurnal Organicheskoi Khimii, 2012, Vol. 48, No. 12, pp. 1598–1599.