Improved Synthesis of Methyl 3-oxo-2,6,6-trimethylcyclohex-1-ene-1-carboxylate, an A-ring intermediate for (±)strigol

Abstract

Methyl 3-oxo-2,6,6-trimethylcyclohex-1-ene-1-carboxylate was synthesised over eight steps from the starting material of citral instead of α-ionone. KMnO4, HC(OEt)3 and O2/TEMPO/CuCl were substituted for NaIO4, CH3I and pyridinium chlorochromate, respectively. Every step was simplified and gave a 48% overall yield. The procedure is suitable for large scale production.