The present invention provides compounds that are glycine transporter 1 (hereinafter referred to as GlyT-1) inhibitors and are therefore useful for the treatment of diseases treatable by inhibition of GlyT1 such as cognitive disorders associated with Schizophrenia, ADHD (attention deficit hyperactivity disorder), MCI (mild cognitive impairment), and the like. Also provided are pharmaceutical compositions containing such compounds and processes for preparing such compounds.