- Triflic acid catalyzed reductive coupling reactions of carbonyl compounds with O-, S-, and N-nucleophiles
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Highly efficient metal-free reductive coupling reactions of aldehydes and ketones with a range of nucleophiles in the presence of triflic acid (1-5 mol %) as the catalyst are presented. The reactions can be performed at ambient temperature without exclusion of moisture or air. A range of symmetrical and unsymmetrical ethers were obtained by this method in high yields and short reaction times. For the first time, the influence of additional functionalization has been studied. Furthermore, the formation of thioethers from ketones (by addition of unmodified thiols) and of sulfonamides from either aldehydes or ketones has been achieved under catalytic conditions.
- Gellert, Beate A.,Kahlcke, Nils,Feurer, Markus,Roth, Stefanie
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supporting information; experimental part
p. 12203 - 12209
(2011/11/07)
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- Bismuth trichloride catalyzed efficient reductive etherification of carbonyl compounds with alcohols: A novel method for preparation of symmetrical and unsymmetrical ethers
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The reductive homocoupling of a carbonyl compound and heterocoupling of a carbonyl compound with a non-protected alcohol were both effected smoothly at room temperature with triethylsilane in the presence of a catalytic amount of bismuth trichloride to afford the corresponding ethers in good yields.
- Wada, Makoto,Nagayama, Sonoe,Mizutani, Kaori,Hiroi, Ryoichi,Miyoshi, Norikazu
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p. 248 - 249
(2007/10/03)
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- Hydrodehalogenation of 1,1-dibromocyclopropanes by Grignard reagents promoted by titanium compounds
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1,1-Dibromocyclopropanes are converted into the corresponding monobromocyclopropanes (as mixtures of stereoisomers where appropriate) by reaction with 1.0-1.3 mol equiv. of ethylmagnesium bromide and 2-10 mol% titanium isopropoxide for 90%). With ethylmagnesium bromide, the reaction occurs very slowly in the absence of catalyst; with methylmagnesium bromide, the reaction does occur in the absence of catalyst, but is only slightly promoted in the presence of titanium isopropoxide. Reactions with a number of other Grignard reagents are also discussed. In the case of phenethylmagnesium bromide, the major product containing the phenethyl-group is ethylbenzene, together with small amounts of styrene and ethyl 4-phenyl-2-butyl ether, a product of trapping of the solvent, ether. In other cases, relatively large amounts of a diether, formally derived by hydrogen ion adjacent to the ether oxygen followed by dimerisation, are isolated. No products were identified incorporating the cyclopropane and either the Grignard alkyl group or the solvent. Labelling studies indicate that the hydrogen introduced into the cyclopropane is not derived from either the α- or β-positions of the Grignard reagent. When the reduction is carried out with phenethylmagnesium bromide in d8-tetrahydrofuran both monobromides contain deuterium.
- Dulayymi, Juma'a R. Al,Baird, Mark S.,Bolesov, Ivan G.,Nizovtsev, Alexey V.,Tverezovsky, Viacheslav V.
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p. 1603 - 1618
(2007/10/03)
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- Reaction of Acetals with Grignard Reagents
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The reaction of dialkyl acetals derived from α,β-unsaturated aldehydes with Grignard reagents using TiCl4 in THF afforded the cross coupling products, allyl ethers, in high yields.The TiCl4-promoted reaction of alkyl 2,4-dichlorophenyl acetals, synthesized from 3,4-dihydro-2H-pyran or ethyl vinyl ether and 2,4-dichlorophenol, with Grignard reagents in THF at low temperature afforded the corresponding unsymmetrical ethers in high yields.When alkyl 2,4-dichlorophenyl acetals, synthesized from aromatic aldehyde or vinyl ethers and 2,4-dichlorophenol, were treated with Grignard reagents in benzene or toluene at room temperature in the absence of TiCl4, the cross coupling reaction took place and the corresponding ethers were isolated in good yields.
- Ishikawa, Hiroshi,Mukaiyama, Teruaki,Ikeda, Shigeru
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p. 776 - 780
(2007/10/02)
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