Disclosed are compounds of formula (I) and methods for their preparation. The compounds are useful as H3 receptor antagonists / inverse agonists. A specific example is 2-[2-methyl-4-((2S,3'S)-2-methyl-[1,3']bipyrrolidinyl-1'-yl)-phenyl]-8-oxa-2-azaspiro[4.5]decan-1-one； The compounds can be used to modulate H3 receptor function and thus treat cognitive impairment associated with schizophrenia (CIAS), anxiety disorders such as generalized anxiety, panic disorder and post-traumatic stress disorder, major depressive disorder,dementia of Alzheimer type (OAT), cognitive deficits related to neurological diseases chosen from Alzheimer, Parkinson or Huntington, age related cognitive impairment, mild cognitive impairment, vascular dementia, Lewis Body dementia, cognition associated with cognitive deficits, sleep related disorders, attention deficit hyperactivity disorder and depression, and obesity.
