It can be prepared in two different ways: 1) By oxidation of 3-(3-dimethylaminopropylidene)dibenzo[a,d]cyclohepta-1,4-diene (I) with H2O2 in methanol (1-5). 2) By reaction of 3-(3-bromopropylidene)dibenzo[a,d]cyclohepta-1,4-diene (II) with dimethylhydroxylamine (III) by means of K2CO3 in refluxing acetone (1-3).