Palladium-Catalyzed Allylic Alkylation of α-Sulfinyl Carbanions under ­Biphasic Conditions

Abstract

Palladium-catalyzed allylic alkylation of α-sulfinyl carbanions can take place under biphasic conditions. These new conditions provide a simple, mild and efficient route to allylated sulfoxides in good yields. The reaction tolerates a wide variety of EWG groups as additional carbanion stabilizing groups such as ­ester, acetyl, cyano, amide, sulfonyl and sulfinyl functions.

Key words

palladium - sulfoxides - carbanions - catalysis - allylic alkylation

References and Notes

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• 8a

  This substrate was prepared by oxidation of the corresponding thioether (see ref. 8b) with Oxone^® and wet alumina (see ref. 8c).

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11

General Procedure for Palladium-Catalyzed Allylic Allylation of α-Sulfinyl Activated Carbanions under Biphasic Conditions. To a solution of [Pd(C₃H₅)Cl]₂ (2 mol%) in CH₂Cl₂ (500 µL) dppe (5 mol%) was added. After 5 min stirring at r.t., the allyl acetate (1 mmol), a CH₂Cl₂ (4.5 mL) solution of the sulfoxide (1.1 mmol), H₂O (5 mL), and KOH (50% aq solution, 2 mmol) were successively added. The resulting biphasic system was vigorously stirred at r.t. for the indicated reaction time. The aqueous phase was extracted three times with CH₂Cl₂. The collected organic phases were dried over MgSO₄ and the solvent was removed in vacuo. The crude product was purified by flash chromatography.

14

This substrate has been prepared by oxidation of the corresponding thioether with Oxone^® and wet alumina (see ref. 8).

20

For pK_a values of compounds strictly related to 1f and 1h see: http://www.chem.wisc.edu/areas/reich/pkatable/.