- 1-Bromo-1-lithioethene: A practical reagent for the efficient preparation of 2-bromo-1-alken-3-ols
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(Matrix presented) A reliable preparative-scale synthesis of 1-bromo-1-lithioethene is reported. This reagent undergoes clean 1,2-addition with a range of aldehydes and ketones at -105°C to afford the corresponding 2-bromo-1-alken-3-ols in moderate to excellent yield. Efficient diastereoselective addition to α-siloxy and α-methylcyclohexanones, as well as protected 3-keto furanose sugars, is achieved in the presence of 10 mol% CeBr3. The resulting bromoallylic alcohol adducts have considerable potential as synthetic building blocks.
- Novikov, Yehor Y.,Sampson, Paul
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p. 2263 - 2266
(2007/10/03)
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- Prins-pinacol spiroannulations
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Lewis acid-promoted cyclizations of methylenecyclohexane siloxy acetals 14, 15, and 21 afford spiro[4.5]decanones 22, 25, and 29 in good yield. In all cases, exclusive pinacol rearrangement of C-1 of the original three- carbon acetal side chain is observed suggesting that pinacol rearrangement of the intermediate 9-decalyl cation occurs more rapidly than conformational equilibration. This selectivity should allow Prins-pinacol spiroannulations to be employed in a predictable fashion to construct stereochemically complex spirocycles.
- Minor, Keith P.,Overman, Larry E.
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p. 8927 - 8940
(2007/10/03)
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- Sensitized Photooxygenation of Silyl Enol Ethers of Cyclic Ketones
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α,β-Unsaturated and α-hydroxy ketones are accessible in prototropic ene-reactions with singlet oxygen by sensitized photooxygenation of cyclic silyl enol ethers and subsequent reduction and solvolysis.In a competing silatropic ene-reaction α-silyloxyketones are formed.Formation of different products depends on ring size, configuration and substitution.At C-6 chirally substituted 2-cyclohexenones are synthesized for the first time by sensitized photooxygenation of chiral silyl enol ethers of optically active starting ketones.
- Friedrich, Edgar,Lutz, Werner
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p. 1245 - 1263
(2007/10/02)
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- A new, facile synthesis of the 3-methyl-2(5H)-furanoid structural unit from ketones
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The 3-methyl-2(5H)-furanoid structural unit is prepared from ketones via 1,4-rearrangement of siloxyalkenes on peroxidation and via oxetene rearrangement of 1-diethylaminopropyne in 53-58% overall yield.
- Pennanen, Seppo I.
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p. 657 - 658
(2007/10/02)
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