Gold-Catalyzed Efficient Preparation of Linear α-Iodoenones from Propargylic Acetates
Meng Yu, Guozhu Zhang and Liming Zhang*
*Department of Chemistry & Biochemistry, University of California, Santa Barbara, CA 93106-9510, Email: zhangchem.ucsb.edu
M. Yu, G. Zhang, L. Zhang, Org. Lett., 2007, 9, 2087-2090.
A catalytic amount of Au(PPh3)NTf2 converts readily accessible propargylic acetates into versatile linear α-iodoenones in good to excellent yields. Very good Z-selectivities are observed for aliphatic propargylic acetates.
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Preparation of α-iodoenones
To a solution of propargylic acetate (0.2 mmol) in anhydrous acetone (4 mL) cooled in an ice-water bath were added H2O (0.005ml, 1.39 eq) and Au(PPh3)NTf2 (0.05 M in acetone, 0.08 mL). The solution was treated with NIS (0.24 mmol, 1.2 eq). The reaction was stirred for two hours before quenched with NEt3 (1 drop) and aqueous Na2S2O3 (5 mL). The mixture was extracted with Et2O (3 x 8 mL). The combined organic phases were washed with H2O (10 mL) and brine (10 mL), dried with anhydrous MgSO4, and filtered. The filtrate was concentrated, and the residue was purified through silica gel flash column chromatography (hexanes/ethyl acetate = 50/1) to yield the desired α-iodo-α,β-unsaturated ketones.
L. Ye, L. Zhang, Org. Lett., 2009, 11, 3646-3649.