Reactions of Aldehydes with Monosubstituted Malonic Acids
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The primary purpose of the present work was the extension of the Doebner modification of the Knoevenagel reaction to mono-substituted malonic acids. The Doebner modification has been limited in the past to the reactions of malonic acid with aliphatic and aromatic aldehydes malonic acids. Since the Doebner modification of the Knoevenagel reaction usually gives high yields of a unsaturated acids directly, it was hoped that extension to monosubstituted malonic acids would make available a general and possibly superior method of preparing substituted and unsaturated acids.The reaction of benzaldehyde and ethylmalonic acid in pyridine solution in the presence of piperidine was studied in an effort to find acceptable general conditions for the reaction. The conditions found satisfactory involved treating ethylmalonic acid and piperidine in equimolar amounts with benzaldehyde in pyridine solvent at steam bath temperature. The molar ratio of ethylmalonic acid to benzaldehyde was two to one. These conditions were applied to the reactions of methylmalonic acid with twenty-nine aromatic aldehydes. The yields of methyleinnamic acids were generally excellent and were superior in all cases to those reported using other preparative methods. The electronic nature of the ring substituent of the aldehydes investigated did not markedly influence the yields of methylcinnamic acids. There appeared to be a tendency toward improved yields when electron withdrawing groups, e.g., nitro, chloro, bromo, were present in the benzenoid nucleus. At least in the two cases tested viz., 2,4,6-trimethylbenzaldehyde and 2,4,6-trimethyl-3,5- dintrobenzadehyde, the presence of two ortho methyl groups resulted in a decreased yield.[Truncated]
Thesis (Ph.D)--Boston University
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