Reactions of grignard reagents with bis- or mono-phosphonium ions in situ generated from Bu3P and dicarboxylic acid dichlorides or omega-ethoxycarbonyl alkanoyl chlorides as a novel method to obtain diketones and ketoesters.
Reactions of Grignard reagents with bis-phosphonium or mono-phosphonium ions in situ generated from BusP and ClCO(CH2)nCOCl (5) or ClCO(CH2)nCO2Et (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 degrees C followed by addition of n-BuMgCl (2.0 eq) gave the corresponding diketone in good yield. When a mixture of BusP 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 alpha-diketones or alpha-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 degrees C afforded a mixture of 2,7-undecanedione and the corresponding two symmetrical diketones, with the yield of the unsymmetrical diketone being 36%.
Maeda
H
H
Graduate School of Pharmaceutical Sciences, Osaka University, Suita, Japan. h-maeda@phs.osaka-u.ac.jp
Hino
N
N
Yamauchi
Y
Y
Ohmori
H
H
D002712:Chlorides / Q000737:chemistry; D003998:Dicarboxylic Acids / Q000737:chemistry*; D004952:Esters; D007202:Indicators and Reagents / Q000737:chemistry*; D007477:Ions; D007659:Ketones / Q000737:chemistry*; D009682:Magnetic Resonance Spectroscopy; D010755:Organophosphates / Q000737:chemistry*; D009943:Organophosphorus Compounds / Q000737:chemistry*; D013055:Spectrophotometry, Infrared
D002712:Chlorides; D003998:Dicarboxylic Acids; D004952:Esters; D007202:Indicators and Reagents; D007477:Ions; D007659:Ketones; D010755:Organophosphates; D009943:Organophosphorus Compounds; C113117:tributylmethyl phosphonium chloride; C009524:tributyl phosphate