Über die Abspaltung von Formaldehyd aus β‐Oxoalkohol‐ und Tetrahydro‐γ‐pyron‐Verbindungen, III. Die Synthese der Isomeren 3.5.5‐Trimethylol‐Tetrahydro‐Desoxy‐Patulinsäure‐Lactone

Abstract

Abbild. 3) eine Verbindung C10Hj406 vom Schmp. 128--130", die sich durch ihre Reaktionen als der Methylenather der kiirzlich beschriebenen 1) 5.5-Dimethylol-dihydrodesoxy-paticlinsiiure (XIX) (IR-Spektrum s. Abbild. 4) erwies und die daher bei der Eisessig-Schwefelsaure-Spaltung und anschlieknder Verseifung des nicht kristalli- 91-

Sulfuric acid and Amberlyst-H+ catalyzed condensation reactions of renewable keto acids with paraformaldehyde: synthesis of a new dispiro bis-lactone ring system 2,9,13-trioxadispiro[4.1.4.3]tetradecane-3,6,10-trione

“…26 Absorption corrections were applied by a semi-empirical approach using SADABS, 27 In our experiments we have studied the condensation between LA and paraformaldehyde under neat conditions, omitting the use of glacial acetic acid as a solvent to avoid the formation of acetate products as seen in previous studies. [20][21][22][23] In addition, we have used at least six equivalents of formaldehyde as 5 equivalents are required for complete hydroxymethylation and another equivalent for 1,3-dioxane ring closure. However the early attempts with exactly six equivalents gave much lower yields and experiments using seven equivalents of para formaldehyde produced the highest yields.…”

“…19 The aldol condensation reactions between LA and formaldehyde were rst reported in 1955, then during the period of 1955-1960, Olsen and co-workers published on their attempts to characterize various incomplete aldol condensation products resulting from sulphuric acid catalyzed condensation of formaldehyde with LA. [20][21][22][23] Since these early experiments were carried out in glacial acetic acid medium with limited amount of formaldehyde, complex mixtures of products were formed with different degrees of condensation, together with their acetate derivatives as well. Then in 1964 Crabb and Cookson mentioned a LAformaldehyde condensation product in a spectroscopy study, where they used the 1 H NMR coupling constants to identify 1,3-dioxalane and 1,3-dioxan rings, reporting only the proton coupling constants of the 1,3-dioxan ring protons in the condensation product.…”