74333-61-2Relevant academic research and scientific papers
Stereochemistry of Thermolytic Base-catalysed Decarboxylation to form Cojugated Diene-Acids: Synthesis using Ethylidenemalonic Ester Condensation
Crombie, Leslie,Crombie, W. Mary L.
, p. 1267 - 1274 (2007/10/02)
The condensation of aromatic aldehydes with ethylidenemalonic ester in the presence of benzyltrimethylammonium hydroxide leads to 2(E),4(E)-half-esters, which are decarboxylated in refluxing pyridine to 2(E),4(E)-esters.When decarboxylated by thermolysis in quinoline at 130 deg C cinnamylidenemalonic acid gives almost pure 5-phenylpenta-2(Z),4(E)-dienoic acid which slowly stereomutates, but on continued heating at 170 deg C it passes over to give almost pure 2(E),4(E)-acid.In pyridine near its boiling point, however, the malonic acid is converted into a 64:36 mixture of 2(Z),4(E)-:2(E),4(E)-acids, the composition of which does not change on continued refluxing.The use of carboxy-labelled dideuteriomalonic acid in the pyridine reaction leads to 5-phenylpenta-2(Z),4(E)-dienoic acid and its 2(E),4(E)-stereoisomer, each having similar ca. 2.1 α/γ deuterium labelling.The latter stereoisomer does not arise by stereomutation, and a dual pathway originating from a common deuteriated lactone is proposed.Decarboxylation of the deuteriomalonic acid in quinoline at 130 deg C, giving almost pure 2(Z),4(E)-dienoic acid with ca. 2:1 α/γ labelling, involves only one of the pathways.The ethylidenemalonic acid method is suitable for the preparation of 2(E),4(E)-half-esters and 5-phenylpenta-2(Z),4(E)-dienoic acids having both electron-withdrawing as well as electron-releasing aryl substituents. 2(Z),4(E)-Sorbic acid can also be made from the corresponding malonic acid by quinoline-catalysed decarboxylation, whereas the classical pyridine-catalysed Doebner reaction forms almost entirely 2(E),4(E)-sorbic acid.
