Upgrading Y to J using miles
 

Does anyone have experience upgrading a full fare ONE WAY economy class (Y ) to business (J) with miles?

I have an upcoming long haul flight from JFK/LGA>PVG in economy class paid by my company and am looking for the easiest way/airline/alliance to upgrade with miles. Also, is it possible to upgrade via alliance partners? For example, transfer UR points to Flying Blue and upgrade Korean Air?

I have a ton of UR and Marriott points at my disposal (prefer using UR) but would like to find an optimum way to redeem. Considering mostly Star Alliance or Skyteam, preferred airlines are KE, NH, CX, UA, MU, AC. Thanks.