the present invention provides , in part , compounds of formula i : n - oxides thereof , and pharmaceutically acceptable salts of the compounds or n - oxides ; processes for the preparation of ; intermediates used in the preparation of ; and compositions containing such compounds , n - oxides , or salts , and their uses for treating m1 - mediated disorders including , e . g ., alzheimer &# 39 ; s disease , schizophrenia , pain , addiction , and a sleep disorder .