That would be pretty tough. With QRs ability to rebook flights for free these dates, have you looked into whether they will let you rebook into YYZ-YUL-DOH-LHE? Alternatively, just drive to montreal and take the flight from there - since you can change the origin for free these days, they would let you change the origin to YUL? 90 minutes seems pretty short to do that transit, depending on whether you will need to get landside, recheck in and so on. I haven't transited through the states before, so I'm not sure what the requirements might be.