After beating SPFL newboys Kelty Hearts by just a single goal on Friday, United looked like they were in for another League Two slog as Kane Hester gave the visitors a shock fourth-minute lead at Tannadice.
It would last only until the 19th minute when Lawrence Shankland got the first of two goals on the day. The striker made it 3-1 later in the half after Nicky Clark scored from Peter Pawlett’s assist.
The ex-Aberdeen midfielder got in on the act himself to make it 4-1 before Shankland turned provider for youngster Kieran Freeman to make it five. Freeman then set up Chris Mochrie for the sixth and final home goal for Group B's leaders.
It wouldn’t be quite so straight-forward for the other Scottish Premiership club in action on Wednesday as Motherwell made difficult work of their trip to Queen’s Park in Group F.
Playing in their first match of the season, Graham Alexander’s side had to rely on an early goal from Steven Lawless to secure themselves all three points.
Elsewhere in Group B, there was plenty of drama in Arbroath v East Fife. The hosts had made all five substitutes when goalkeeper Calum Antell was sent off on 68 minutes. Outfielder David Gold was moved between the sticks as Dick Campbell’s side saw out the rest of the game with ten men. They not only kept a clean sheet, but won the match 2-0 thanks to late strikes from Dale Hilson and Luke Donnelly.