Chromium-Catalyzed Linear-Selective Alkylation of Aldehydes with Alkenes
We developed a chromium-catalyzed, photochemical, and linear-selective alkylation of aldehydes with alkylzirconium species generated in situ from a wide range of alkenes and Schwartz's reagent. Photochemical homolysis of the C-Zr bond afforded alkyl radicals, which were then trapped by a chromium complex catalyst to generate the alkylchromium(III) species for polar addition to aldehydes. The reaction proceeded with high functional group tolerance at ambient temperature under visible-light irradiation.
The invention relates to a process for preparing Grignard compounds of the formula I. The invention additionally relates to compounds of the formula I and to polymer-bound compounds of the formula Ia. The invention further relates to the use of the process for preparing substance libraries and to the use of the compounds of the formulae I and Ia in chemical synthesis.
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Page/Page column 11
(2008/06/13)
The Barbier - Grignard-type carbonyl alkylation using unactivated alkyl halides in water
The aqueous Barbier-Grignard-type alkylation of aldehydes with unactivated alkyl iodides and bromides was developed. By using a combination of zinc and cuprous iodide, catalyzed by indium(I) chloride, we successfully added tertiary, secondary, and primary alkyl halides to various aromatic aldehydes in 0.07 M aqueous Na2C2O4. A mechanistic rationale for the success of the reaction has been proposed. Copyright
Keh, Charlene C. K.,Wei, Chunmei,Li, Chao-Jun
p. 4062 - 4063
(2007/10/03)
Selective halogen - Magnesium exchange reaction via organomagnesium ate complex
Halogen-magnesium exchange of various aryl halides is achieved with a magnesium ate complex at low temperatures. Tributylmagnesate (nBu3MgLi) induces facile iodine-magnesium exchange at -78 °C. Dibutylisopropylmagnesate (iPrnBu2MgLi) is more reactive than nBu3MgLi, and this reagent accomplishes selective bromine-magnesium exchange at -78 °C. This procedure is utilized for the preparation of various polyfunctionalized arylmagnesium species. The exchange of alkenyl halides using this method proceeds with retention of configuration of the double bond.
Inoue,Kitagawa,Shinokubo,Oshima
p. 4333 - 4339
(2007/10/03)
Halogen-magnesium exchange via trialkylmagnesates for the preparation of aryl- and alkenymagnesium reagents
Significantly better than simple Grignard reagents are the trialkylmagnesium-ate complexes in the halogen-metal exchange reaction of aryl or alkenyl halides to the corresponding magnesates (see reaction scheme). The subsequent reaction of these ate complexes with electrophiles proceeds in good to excellent yields, and a number of functional groups (FG) can be tolerated.
Preparation of highly functionalized Grignard reagents by an iodine-magnesium exchange reaction and its application in solid-phase synthesis
At -40°C aryl iodides that contain other functional groups can be selectively converted into Grignard reagents, which react with electrophiles such as benzaldehyde in the usual manner [Eq. (a)]. Aryl bromides and iodides that are immobilized as esters on a Wang resin behave analogously.
Boymond, Laure,Rottlaender, Mario,Cahiez, Gerard,Knochel, Paul
p. 1701 - 1703
(2007/10/03)
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