117982-92-0Relevant academic research and scientific papers
The Tandem Knoevenagel Hetero Diels-Alder Reaction with a Formylacetic Acid Equivalent. Synthesis of Dihydropyrancarboxylates
Tietze, Lutz F.,Meier, Heinrich,Nutt, Heinrich
, p. 643 - 650 (2007/10/02)
The tandem Knoevenagel hetero Diels-Alder reaction of 4,4,4-trichloro-3-oxobutanal (9) with the aldehydes 10 as well as 16-21 and the enol ethers 6 as well as 28-32 followed by base-catalyzed methanolysis yields the methyl dihydro-2H-pyran-5-carboxylates 15, 22-27, and 33-37.In this reaction 9 is used as an equivalent of the non-stable formylacetic acid, since the trichloromethylcarbonyl moiety can be transformed into an alkoxycarbonyl group by solvolysis with an alcohol.As an example, in a three-component reaction 9 was condensed with propanal (10) in the presence of potassium fluoride to give the activated oxadiene 11 as an intermediate.This reacts with an ethyl vinyl ether (6), which is present as one component in the reaction mixture, to afford the cycloadduct 13 after acidic workup.Methanolysis of 13 in the presence of DBU yields the methyl dihydro-2H-pyran-5-carboxylate 15 in 50percent overall yield.Keywords: Dihydropyrancarboxylates/ Formylacetate/ Haloform clevage/ Hetero Diels-Alder reactions/ Knoevenagel reaction
