Ketones, trichlorostannyl

Similar dehydrotrichlorostannation of j9-trichlorostannyl ketones by DMSO requires prolonged heating at 60°C. 

Heating of the 3-trichlorostannyl ketone in DMSO also results in formation of 2-methylencyclohexanone (Eq. (25), Table 4) [31], which is formally the reverse reaction of a hydrostannylation of the enone with HSnCl3. This alternative route... 

Dehydrostannation ot, -enones.1 A novel route to a-methylene ketones involves cleavage of 1-alkyl-1-silyloxycyclopropanes with SnCl4 in CH2C12 at 15° to provide p-trichlorostannyl ketones in 70-90% yield. These products undergo dehydrostannation when treated with excess DMSO in CHC13 at 60° to furnish a-methylene ketones in usually good yield. Pyridine and DMF are less useful than DMSO. 

The /9-tributylstannyl ketones are conveniently prepared by the chemoselective Grig-nard alkylation at the Sn atom of the corresponding /9-trichlorostannyl ketones, which... 

Trichlorotitanium enolates. These Ti enolatcs are formed generally in high yield by reaction of enol silyl ethers with TiCE at 20-35° in CHiCE." The corresponding reaction with SnCE results in a-trichlorostannyl ketones." The stability of these Ti enolates varies from a few seconds to a few days, depending on the structure. As in the case of... 

Similarly, tin(IV) chloride opens the less highly substituted bond of siloxycyclopropanes to afford thermally stable ) -trichlorostannyl ketones. Facile dehydrostannylation takes place upon treatment with > 3 equivalents of dimethyl sulfoxide in chloroform or, better, hexane solution at 15-60°C to furnish 2-methylene ketones in high overall yields. This elimination occurs with virtually quantitative yield at 0°C if promoted by bases, preferably by N.N.N .N -X ira-methylethylenediamine. - Examples are the reactions of 24 and 27. ... 

Heating of the 3-trichlorostannyl ketone in DMSO also results in formation of... 

Palladium homoenolates readily undergo p-elimination to give a,P-unsaturated carbonyl compounds. Treatment of a mercurio ketone with a catalytic amount of palladium(II) in the presence of CuCh results in the formation of an enone via a 3-palladio ketone (Scheme 3). Treatment of a silyloxycyclopropane (8) with PdCh also generates in situ a palladium homoenolate which then undergoes -elimination (Scheme 3). Heating a mixture of a 3-trichlorostannyl ketone or aldehyde with DMSO results in the formation of an enone or an enal in excellent yield (Scheme 4). ... 

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