- α- And β-Functionalized Ketones from 1,3-Dienes and Aldehydes: Control of Regio- And Enantioselectivity in Hydroacylation of 1,3-Dienes
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Ketones are among the most widely used intermediates in organic synthesis, and their synthesis from inexpensive feedstocks could be quite impactful. Regio- and enantioselective hydroacylation reactions of dienes provide facile entry into useful ketone-bearing chiral motifs with an additional latent functionality (alkene) suitable for further elaboration. Three classes of dienes, 2- or 4-monosubstituted and 2,4-disubstituted 1,3-dienes, undergo cobalt(I)-catalyzed regio- and enantioselective hydroacylation, giving products with high enantiomeric ratios (er). These reactions are highly dependent on the ligands, and we have identified the most useful ligands and reaction conditions for each class of dienes. 2-Substituted and 2,4-disubstituted dienes predominantly undergo 1,2-addition, whereas 4-substituted terminal dienes give highly enantioselective 4,1- or 4,3-hydroacylation depending on the aldehyde, aliphatic aldehydes giving 4,1-addition and aromatic aldehydes giving 4,3-addition. Included among the substrates are feedstock dienes, isoprene (US$1.4/kg) and myrcene (US$129/kg), and several common aldehydes. We propose an oxidative dimerization mechanism that involves a Co(I)/Co(III) redox cycle that appears to be initiated by a cationic Co(I) intermediate. Studies of reactions using isolated neutral and cationic Co(I) complexes confirm the critical role of the cationic intermediates in these reactions. Enantioselective 1,2-hydroacylation of 2-trimethylsiloxy-1,3-diene reveals a hitherto undisclosed route to chiral siloxy-protected aldols. Finally, facile syntheses of the anti-inflammatory drug (S)-Flobufen (2 steps, 92% yield, >99:1 er) and the food additive (S)-Dihydrotagetone (1 step, 83% yield; 96:4 er) from isoprene illustrate the power of this method for the preparation of commercially relevant compounds.
- Parsutkar, Mahesh M.,Rajanbabu, T. V.
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supporting information
p. 12825 - 12835
(2021/08/30)
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- Water-Accelerated Nickel-Catalyzed α-Crotylation of Simple Ketones with 1,3-Butadiene under pH and Redox-Neutral Conditions
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We report a nickel/NHC-catalyzed branched-selective α-crotylation of simple ketones using 1,3-butadiene as the alkylation agent. This reaction is regioselective and operated under pH and redox-neutral conditions. Water was used as the sole additive, which significantly accelerates the transformation.
- Chen, Tiantian,Dong, Guangbin,Xing, Dong,Yang, Haijian,Yang, Yang
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p. 4238 - 4243
(2020/05/05)
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- gamma-alkenyl ketone and preparation method thereof
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The invention discloses a gamma-alkenyl ketone preparation method, wherein the target product can be obtained at high yield and high regioselectivity by using acetophenone and 1,3-butadiene as raw materials in the presence of an organic solvent, a catalyst, an additive and a ligand. According to the invention, the method has advantages of high atom economy, high regioselectivity, high yield and the like, can achieve the efficient conversion from a cheap basic organic chemical product 1,3-butadiene to high-added-value gamma-alkenyl ketone, and uses the cheap catalyst, so that the reaction conditions are neutral and mild, and the experimental operation is safe and simple; and the synthesized gamma-alkenyl ketone is a useful synthetic intermediate, can be subjected to a series of conversionsto obtain a series of drug molecule precursors or key intermediates, and has wide application prospect.
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Paragraph 0031; 0156-0159
(2020/02/29)
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- Regioselective α-alkylation of silyl enolates using a mild catalyst- ZnCl2 doped on acidic alumina
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ZnCl2 doped acidic alumina used as a solid support acts as a better Lewis acid in the S(N)1 reaction of trimethyl silyl enol ethers with 30, allylic and benzylic halides to yield exclusively the substituted product in excellent yields. This method has been employed for the synthesis of monocyclic sesquitepene hydrocarbon, (+)-β-bisabolene and a monoterpene, 2,6-dimethyl-7-octen-4-one.
- Kad,Singh, Vasundhara,Khurana, Anupam,Chaudhary, Sangeeta,Singh, Jasvinder
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p. 3439 - 3442
(2007/10/03)
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- Synthesis of dihydrotagetone (2,6-dimethyloct-7-en-4-one)
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The acyclic monoterpene dihydrotagetone (2,6-dimethyloct-7-en-4-one) has been prepared from isobutyl methyl ketone in two stages. The key step involves a simple extension of the Carroll reaction.
- McAndrew,Riezebos
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p. 367 - 369
(2007/10/12)
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- TERPENOIDS-58
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Two new syntheses of the acyclic monoterpenic, pleasant smelling ketone 2,6-dimethyl- 7- octen- 4- one from Tagetes glandulifera are described. In the first synthesis the starting compound ethyl 2,6- dimethyl-4- keto- heptanoate on ketalization, reduction and subsequent Cr//2O//3-oxidation furnishes the ketal- aldehyde. Witting reaction on the ketal-aldehyde with methlenetriphenyl- phosphorane affords 2,6-dimethyl- 4,4- ethylenedioxy- 7- octene.
- VIG OP,MATTA KL,BHATIA MS,ANAND RC
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p. 107 - 108
(2007/10/10)
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