An Improved Two-step Route for the Preparation of β-Diketones from Aldehydes and its Application to the Synthesis of β-Damascone
α-Diazo-β-hydroxyketones, obtained by condensation of aldehydes with 1-diazo-1-lithioacetone, are efficiently transformed into the corresponding β-diketones by exposure to rhodium(II) acetate, The sequence is applied to a new synthesis of β-damascone (10).
A new synthetic route to β-damascone (7) starting from β-cyclocitral is described.The crucial intermediate 9-oxo-dihydro-β-damascone (3) is prepared in two steps by treatment of (1) with 1-diazo-1-lithioacetone followed by the rhodium (II) acetate conversion of 3-diazo-4-hydroxy-4(2,2,6-trimetylcyclohex-6-enyl) butan-2-one (2) thus formed to (3).