Provided herein are compounds of formula A-L-B, and pharmaceutically acceptable salts and stereoisomers thereof, wherein A is  wherein L, B and R3 are defined herein, methods of their synthesis, pharmaceutical compositions comprising the compounds, and methods of their use. The compounds and compositions provided herein are PDE-10 inhibitors and useful, e.g., for the treatment, prevention, and/or management of various disorders, such as CNS disorders and metabolic disorders, including, but not limited to, e.g., neurological disorders, psychosis, schizophrenia, obesity, and diabetes.