Syracuse reached the semifinals by fighting off Pittsburgh 62-59. The other quarterfinal contests saw Louisville eliminate Villanova 74-55 and Notre Dame knock off Marquette 73-65.
Cincinnati was within five points at halftime against Georgetown, but went on to lose for the seventh time in 11 games. The Bearcats reached the tournament final last year for the first time since joining the league.
Porter scored 18 points while Markel Starks had 14 for the Hoyas (25-5), who shared the regular-season title with Louisville and Marquette.
Syracuse, ranked 20th in the country, again rode the hot shooting of James Southerland to its narrow win over Pittsburgh.
Southerland made 6-of-9 from long range in a second-round win over Seton Hall and he was 6-of-6 against the Panthers. Syracuse (25-8) will be meeting Georgetown for the third time when they play in the semifinals.
Pittsburgh and Syracuse are both leaving the Big East after this season to play in the Atlantic Coast Conference.
Louisville (27-5) put on a strong defensive showing in defeating Villanova. The Cardinals (27-5) forced 25 turnovers and held the Wildcats to 39 percent shooting.
Russ Smith led Louisville with 28 points, 12 of which came on 3-point shots. Villanova had surprised Louisville in their lone regular-season meeting.
Louisville and Notre Dame will meet in Friday's second semifinal game after the Fighting Irish got past Marquette.
Notre Dame (25-8) got 18 points from Pat Connaughton but shot just 40 percent from the field. The Irish, however, hit nine of their last 10 foul shots to protect their lead down the stretch.