Sky News report that United are about to offer £500k for the 25-year-old striker.
The former Hartlepool and Luton forward is the O's top scorer with 11 goals this season.
It should be 12, but he had a perfectly good goal chalked off at Elland Road earlier in the season.
Assistant boss Dave Bassett was at Brisbane Road last night as Orient beat Tranmere 3-0 in a League One fixture to go level on points with the Whites. Unfortunately Boyd was not playing due to injury.