1975 Volume 48 Issue 6 Pages 1892-1896
A new synthesis of 2-hydroxy-3-methyl-2-cyclohexen-1-one (1) is described. The Mannich reaction of cyclohexane-1,2-dione (2) or 2-morpholino-2-cyclohexen-1-one (3) with morpholine and formalin gave a Mannich base (4), which was then hydrogenolized to afford 1. However, the Mannich reaction of 1 merely gave a bis-Mannich base (22), which was then similarly hydrogenolized to afford 3,6-dimethyl-2-hydroxy-2-cyclohexen-1-one (7) along with 3,6-dimethyl-2-hydroxy-6-morpholinomethyl-2-cyclohexen-1-one (26); 2-hydroxy-3,6,6-trimethyl-2-cyclohexen-1-one could not be obtained under these conditions. The Mannich reaction of other alicyclic α-diketones and the hydrogenolysis of their Mannich bases are also described.
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