What is the product formed after nitrosation of ketones (HNO2 + ketone)?
Hydrolysis of the ketone oxime gives the 1,2-diketone as reported in this Synlett reference: 


  Treatment of alpha-methylene ketones with excess sodium nitrite and
  aqueous HCl in THF at reduced temperature provieds an effective tool
  for the preparation of a variety of 1,2-diketones