Structure of β-Acylacrylic Acids
IN previous publications1–5 the β-formyl-, β-acetyl- and β-pivaloyl-acrylic acids were investigated by means of their spectra in the ultra-violet and infra-red. This work has been extended to comprise the α-methyl-β-acrylic acid6,7. In regard to cis–trans isomerism and open or cyclic structure for the preparations used, the infra-red spectra (in the case of acid (5) also by means of the nuclear magnetic resonance) have confirmed the following structures : (1) β-Formylacrylic acid, m.p. 53–56° C.: cyclic, cis (2) β-Acetylacrylic acid, m.p. 122–125° C.: trans (probably with a smaller amount cis-open acid) (3) β-Pivaloylacrylic acid, m.p. 84–85° C.: cyclic, cis (4) β-Pivaloylacrylic acid, m.p. 94–95° C.: trans (5) α-Methyl-β-acetylacrylic acid, m.p. 98–101° C.: cyclic, cis
The Differential Calorimetric Study of the Reactivity of Unstable Compounds
The detection of unstable intermediates in chemical, photochemical, and radiation-chemical reactions can be greatly facilitated by the use of thermoanalytical methods. Special advantages are offered by differential thermal analysis (DTA), since it permits fast, easy investigation, from about −150°C upward in some cases, over a wide temperature range. In this way processes that under normal conditions follow one another with immeasurable rapidity can be separated on the basis of their different temperature dependences. The great sensitivity of the method also allows the use of very dilute solutions, so that the studies can be confined to unimolecular processes. 
 
 
 
The value of the method for the determination of energetic and kinetic data is illustrated by its application to the photochemically obtanable, unstable, ozonide-like epidioxydihydrofurans.
One-pot synthesis of annulated pyrido[2,3-d:6,5-d]dipyrimidine derivatives using nitrogen based DBU catalyst in aqueous ethanol medium
Abstract We have reported DBU as an efficient organocatalyst for one-pot three-component synthesis of annulated pyrido[2,3- d :6,5- d ]dipyrimidine derivatives using aromatic aldehyde, thio-barbituric acid and 6-amino-uracil in aqueous ethanol under reflux. The attractive advantages of this process are mild reaction conditions, environment friendly procedure, short reaction times, easy isolation of products, and excellent yields (72–89%).