Conversion of 5-oxoalkanals to δ-lactones by an intramolecular Tishchenko reaction

Article abstract of DOI:10.1055/s-0036-1589465

Diisobutylaluminum hydride reduction of photoadducts 3 (7,8-tri- and tetrasubstituted l,3,3-trimethyl-2,4-dioxabicyclo-[4.2.0]octan-5-ones), derived from 2,2,6-trimethyl-4/f-l,3-dioxin-4-one (1), gave 6-lactones 7 in good to excellent yields if the workup involved a methanol quench followed by removal of the solvent. We propose that the reaction proceeds by an intramolecular Tishchenko reaction of the intermediate 5-oxoalkanal 5 and is catalyzed by the Lewis acid diisobutylaluminum methoxide, 8. A deuterium labelling experiment supports the mechanistic proposal and the conversion of 5-oxoalkanals other than S illustrates the scope of the procedure. To our knowledge, this is the first report of a true intramolecular Tishchenko reaction.