Diastereoselective synthesis of 5-hydroxy-3-methylalkane-1,6-diones from ketones and acetylene in two atom-economic steps

(2R*,4R*)-2-Acetyl-2,6-diaryl-4-methyl-3,4-dihydropyrans (diastereoselectively synthesized from acetylene and ketones in one synthetic operation) undergo ring opening by aqueous NH₄Cl (MeCN, 80°C, 8h) to afford diastereomerically pure 5-hydroxy-1,6-diketones in 48–89% yields.