Vicinal Difunctionalization of Alkynyl Selenides with Lithium Butylcyano Cuprate and Electrophiles

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• Preparation of Phenylselenoethyne: Acetylene was bubbled through a solution of butylmagnesium bromide (30mmol) in THF (100ml) at −78° until the solution turned dark violet. The reaction mixture was heated to room temperature and then a solution of phenylselenenyl bromide (6.6g, 28mmol) in THF (30ml) was added. After 30min stirring at room temperature the reaction was quenched with saturated ammonium chloride solution (20ml) and exracted with hexane (4×15ml). The organic layer was dried with magnesium sulfate, the solvents were evaporated and the residue was distilled at reduced pressure. Yield: 3.9g (78%), b.p.: 60°/0.2mmHg, 1H NMR (CDCl3, δ, ppm): (3, 14s, 1H); 7,2–7,6(m, 5H)
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• Typical procedure for the vicinal difunctionalization: a) To a suspension of CuCN (0.249g, 2.79mmol) in THF (10ml) under nitrogen at −50°C was added n-BuLi (1.1ml, 2.75mmol of a 2.5M solution in hexane). After 15min stirring the selenoacetylene (2mmol) in THF (lml) was added. After 1h at −50°C the electrophile was added and the mixture was allowed to react as indicated in Table 1. b) Reaction with NH4Cl: to the vinylcuprate prepared as in (a) was added a saturated solution of ammonium chloride (4ml). Then the mixture was diluted with hexane (10ml) and the aqueous phase was extracted twice with hexane (2×10ml). The combined extracts were washed with ammonium hydroxide solution, water and brine, the organic phase was dried over magnesium sulfate, the solvent was evaporated and the residue was flash cromatographed on silica eluting with hexane
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