phile instead of benzaldehyde, reaction with butyllithium under identical conditions proceeded via 1,2-addition to the carbonyl group to give 2-methyl-I -phenyl-3-buten-2-01 (44% yield based on 5a).
This one-pot procedure is operationally convenient and will be especially useful when direct lithium-halogen exchange cannot be resorted to-as in the preparation of benzyl-and allyllithium compounds.i51
Although lithium-selenium exchange has been reported on several occasions,['' examples of lithium-tellurium exchange were hitherto rare.I7I Studies on the scope and limitation of this reaction are currently in progress.
Experimental Procedure
Preparation of the telluride 1, R' =+ R2: la,e,f from lithium butanetellurolate 141 and benzyl bromide, benzyloxymethyl chloride and trimethylsilylmethyl iodide, respectively, in THF; l b from lithium benzenetellurolate and propyl iodide in THF; lc from benzenetellurol and phenylacetylene [8]; Id by a similar method as described in the literature 191 from benzenetellurenyl iodide (PhTel) [lo] and lithium phenylacetylide. Typical reaction starting from a diorganyl telluride 1: A solution of If (1 mmol, 272 mg) in T H F ( 5 mL) was treated at -78°C with a 1 . 6 ~ solution of butyllithium 2 (1 mmol, 0.63 mL), R'=nBu, in hexane. After stirring for 15 min, benzaldehyde ( I mmol, 106 mg) was added by a syringe in one portion, and the reaction mixture then warmed to 25 "C over a period of I h. EtzO (30 mL) and dil. aq. HCI (ca. 0.1 M, 50 mL) were added to the mixture, and the product was extracted with Et20 (50 mL x 3). The ethereal solution was dried over MgSO, and the solvent removed by evaporation. Subsequent radial layer chromatography (silica gel, Et20/he,xane) afforded 171 mg (0.89 mmol; 89%) of 4f together with 238 mg (0.99 mmol) of dibutyl telluride. Typical reaction starting from a halide 5 : To a solution of lithium benzenetellurolate 6 , R'=Ph [4] (prepared in situ from tellurium (2 mmol) and phenyllithium (2 mmol, 1 mL 2.0 M solution in cyclohexane/Et20) in T H F ( 5 mL) was added 342 mg (2 mmol) of benzyl bromide 5a at -78 "C. The mixture was warmed to 25 "C and stirred for 30 min. At this stage, the conversion to the benzyl phenyl telluride la is complete. Further conversion and work-up are the same as in the case of If.