Acylation of silyl enol ethers with acid chlorides

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Oxidation to the sulphoxide followed by in situ elimination of benzenesulphenic For example, when aroyl silanes were treated with a Wittig reagent , none of the expected alkenes was obtained, and the only reaction products isolated were silyl enol ether and triphenylphosphine Scheme 73 , When alkanoyl silanes were treated with Wittig reagents , however, only the normal olefinated vinyl silane products were isolated Scheme 74 Under soluble lithium salt conditions , Z- vinyl silanes were produced with very high selectivities the reaction was used to prepare a pheromone component 50 of the sweet potato leaf folder moth Scheme 75 These compounds could be isolated when tetrabutylammonium difluorotriphenylstannate was used as a catalyst use of tetrabutylammonium fluoride gave the product corresponding to subsequent aldol reaction with the difluoromethyl ketone Scheme 78 m.

Silyl enol ethers are C-acylated by acetyl tetrafluoroborate to give 1,3-diketones. When HSiR. One is a hydrocarbonylation- type reaction , by which formation of the silyl enol ethers 62 via the acylmetal intermediate 61, and the acylsilanes 64 via the acyl complex 63, are expected in practice both reactions are observed. The other possibility is silylformylation to form 65, which is unknown, even though silylformylation of alkynes is known. When Co2 CO 8 is used, the silyl enol ether of aldehyde 66 is obtained [36], However, the silyl enol ether 67 of acylsilane 68 is obtained when an Ir complex is used, and converted to the acylsilane 68 by hydrolysis [37], Procedure A.

A mL flask with a septum inlet and magnetic stir bar was flame dried and flushed with argon. Zinc chloride 0. The flask was removed from the glovebag and connected to a mercury bubbler. This was followed by the introduction of 5. After the flask was cooled to 0 "C, the acid chloride 5. After being stirred 1h at 0 "C, the reaction mixture was allowed to warm to room temperature and was quenched with approximately 10 mL of water.

The layers were separated, and the aqueous layer was washed with methylene chloride. The methylene chloride layers were combined and washed with a saturated sodium hydrogen carbonate solution. The organic extract was dried over sodium sulfate and analyzed by GC for C- and 0acylated ketone. Pure samples of product were obtained for spectral analysis by preparative GC. Procedure B. Antimony trichloride 1.

Methylene chloride 5. The acid chloride 5. After the mixture was stirred 1 h at 0 "C, the flask was warmed to room temperature, and the reaction was quenched with approximately 10 mL of HzO. The method for the work up was as described for procedure A above. Spectral analyses of all products were performed on pure samples obtained by preparative GC. Enol esters obtained by 0-acylation were identified by their mass and 'H NMR spectra.

GC analysis of the crude product after workup showed four components with the following identities and retention times: cyclohexanone 1. Spectral 9 Pray, A. GC analysis of the crude product shows four components [component identity retention time ]: cyclopentanone 1min , cyclopentanone enol acetate 1. Cyclopentanone enol acetate was isolated from the reaction of cyclopentanone trimethylsilyl enol ether and acetyl chloride: 'H NMR CDCl, 5. The crude product was subjected to GC analysis which showed a four-component mixture [identity retention time ]: diethyl ketone 0.

GC analysis of the crude product showed a four-component mixture [identity retention time ]: diisopropyl ketone 0. GC analysis of the crude product mixture showed five components [identity retention time ]: acetophenone 1. GC analysis of the crude product identified four major components [identity retention time ]: isobutyrophenone 2. Spectral analysis of l-phenyl-2,2-dimethyl-l,3-butanedione gave the following: 'H NMR 1. GC analysis of the crude product showed three major components [identity retention time ]: diethyl ketone enol 11 Tavernia, D.

A,; Strom, E. GC analysis of the crude product identified three components [identity retention time ]: diethyl ketone enol 3. GC analysis of the crude products showed four components [identity retention time ]: diethyl ketone 0. GC analysis of the crude product showed four major componenta [identity retention time ]: diethyl ketone 1. Calcd for C10HC, Found C, We thank t h e National Science Foundation for partial support of this work.

Registry No. A 1:l mixture of diastereoisomers was obtained in each case which was conveniently separated by HPLC. The two isomers, erythro e or threo t ,were identified on the basis of their IR and proton NMR spectra.