The invention relates to compounds of the formula I
wherein the variables are as defined in the claims. The compounds are useful in the treatment of a disease where a D4 receptor and/or a 5-HT
2A
receptor is implicated.
The present invention relates to compounds of formula I
wherein R
1
to R
4
are as defined in the description and claims, and pharmaceutically acceptable salts thereof. The compounds are useful for the treatment and/or prevention of diseases which are associated with the modulation of H3 receptors.