A lacklustre opening saw Doncaster race into a 2-0 lead within the first five minutes before Harry Southwick won a penalty, which was calmly dispatched by George Birley.
Doncaster extended their lead with two well-taken goals.
It remained 4-1 until the final quarter, when Birley again provided a calm finish to give Boro hope.
Moments later, Finlay Hopper raced onto a through ball and lobbed the keeper to give Boro a third goal.
With minutes remaining, Birley completed his hat-trick with a fine turn and finish into the bottom corner to take it to 4-4.
Jay Shah collected an attempted through-ball, smashed his kick straight up the pitch for Hopper to smash a volley into the top corner to secure a superb comeback for the Seadogs.
A rare home friendly against strong opposition, i2i Reds, allowed Scarborough u21s Manager Paul Exley the opportunity to give minutes to most of his squad and have a look at several new additions in a competitive game.
While the visitors showed great energy and commitment they were dominated for long periods of the first half by the Seadogs with Ethan Daley-Smith and Mo Abou both seeing plenty of the ball, tormenting the opposition with mesmerizing runs and getting their shots off.
But it was front man Flynn McNaughton, coolly finishing from an acute angle, after a good move down the right, who would open the scoring.
Boro continued to control proceedings in terms of territory with the midfield three and defence comfortable in possession but also showing attacking intent breaking lines with some eye-catching passing from across the back and keeper.
They limited Jono Greening’s I2I Reds' scoring opportunities to corners and a number of set pieces,
Scarborough’s second would come courtesy of a header from Boro skipper Luke Rees and they underlined their dominance as Blake Drury reacted quickest to a deflection off the I2I keeper from a Boro setpiece to close the half 3-0 up.
Both sides made planned wholesale changes at the break and the visitors started brightest looking to unsettle Exley’s men, pressing with intent higher up the pitch and in numbers but would find Scarborough’s keeper and back line composed and up to the challenge looking to take advantage of the resulting space and countering from the back.
The game became more open with chances at both ends, the visiting keeper in particular pulling off a number of impressive stops, with the Seadogs looking to extend their lead and I2I desperate to get a foothold in the game.
A couple of precautionary substitutions as well as additional second-half changes naturally impacted the home side’s fluency in the final 20 minutes but they would see out the game 4-0 victors as McNaughton rounded off the scoring with a sublime low curled strike past the keeper and just inside the post.
Next up for Exley’s men is an away fixture in the u23s league at Pickering Town on Monday night