3-methylcyclohexane-1,2-dione

Conditions: temp:0.00; pressure:0.00; stir:; See reaction.notes.procedure_details.

Procedure: 20.0 g (0.159 mol) of 3-Methyl-1,2-cyclohexanedione and 183.31 g (2.38 mol) of ammoniumacetate are dissolved in 760 ml DMSO. A solution of 27.94 g (0.34 mol) acetaldehyde dissolved in 40 ml DMSO is dropped to the reaction mixture. The reaction is heated for 20 minutes to 40° C., 20 minutes to 60° C. and 40 minutes to 80° C. The reaction is allowed to cool down to rt. 2.5 l saturated sodium chloride solution and ammonia are added to reach a pH of 8-9. The solution is extracted with ethyl acetate and the organic phases are dried over sodium sulfate. The solvent is evaporated under vacuum. The crystalls are filtrated and washed with ethyl acetate and diethyl ether to yield 10.3 g (43.3% of th.) 2,4-Dimethyl-4,5,6,7-tetrahydro-1H-benzimidazole. is dropped to the reaction mixture The reaction is heated for 20 minutes to 40° C., 20 minutes to 60° C. and 40 minutes to 80° C The solution is extracted with ethyl acetate the organic phases are dried over sodium sulfate The solvent is evaporated under vacuum The crystalls are filtrated washed with ethyl acetate and diethyl ether