- Preparation of β-substituted γ-keto esters by the grignard reaction on N-acylpyrazoles
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Various γ-keto esters were prepared by either the alcoholysis of N-(4-oxoalkanoyl)pyrazoles or the Grignard replacement of pyrazole moiety of 4-(N-pyrazolyl)-4-oxoalkanoic esters. By using 3-phenyl-ι-menthopyrazole as a chiral auxiliary, β-substituted γ-keto esters were enantioselectively obtained.
- Kashima, Choji,Shirahata, Yoshie,Tsukamoto, Yoshihiro
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p. 309 - 317
(2007/10/03)
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- Reactions of Grignard reagents with bis- or mono-phosphonium ions in Situ generated from Bu3P and dicarboxylic acid dichlorides or ω-ethoxycarbonyl alkanoyl chlorides as a novel method to obtain diketones and ketoesters
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Reactions of Grignard reagents with bis-phosphonium or mono-phosphonium ions in situ generated from Bu3P and ClCO(CH2)(n)COCl (5) or ClCO(CH2)(n)CO2Et (13) as a tool for preparation of symmetrical diketones or ketoesters were examined. Addition of Bu3P (2.0 eq) to a THF solution of 5 (n=2) at -40°C followed by addition of n-BuMgCl (2.0 eq) gave the corresponding diketone in good yield. When a mixture of Bu3P and the Grignard reagent (2.0 eq each) was added to the dichloride solution at the same temperature, a better result was obtained. The latter method not with PhMgBr but with n-BuMgCl or MeMgBr was shown to be useful for preparation of symmetrical alkanediones and keto alkanoates from various 5 (n=2 - 6) and 13 (n=2 or 3), respectively. For synthesis of α-diketones or α-ketoesters, only PhMgBr entered the reaction, although the yields were not satisfactory. Addition of a mixture of Bu3P (2.0 eq), MeMgBr (1.0 eq) and BuMgCl (1.0 eq) to a THF solution of 5 (n=4) at -40°C afforded a mixture of 2,7-undecanedione and the corresponding two symmetrical diketones, with the yield of the unsymmetrical diketone being 36%.
- Maeda,Hino,Yamauchi,Ohmori
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p. 1196 - 1199
(2007/10/03)
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- Reactions of in situ formed acyl tributylphosphonium ions with Grignard reagents as an effective route to ketones from acid chlorides
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The reactions of acyl tributylphosphonium ions in situ generated from acid chlorides and Bu3P in THF at -22°C with primary alkyl and arylmagnesium halides have proved to be a convenient and simple procedure to prepare ketones from acid chloride in one-pot.
- Maeda, Hatsuo,Okamoto, Junko,Ohmori, Hidenobu
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p. 5381 - 5384
(2007/10/03)
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- Addition of Aldehydes to Activated Double Bonds, XXII. Addition of Aliphatic Aldehydes to α,β-Unsaturated Esters and Nitriles
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Thiazolium salt catalysed addition of aliphatic aldehydes to α,β-unsaturated esters and nitriles leads to γ-ketocarboxylic esters (1-24) and γ-ketonitriles (25-32).
- Stetter, Hermann,Basse, Wolfram,Nienhaus, Juergen
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p. 690 - 698
(2007/10/02)
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