Desmond Bane had 16 points, hitting three free throws with 2.5 seconds left, to help
Frank Mason answered with a pair of free throws for Kansas (28-4), but the Horned Frogs got the ball to Bane in the corner and he was fouled by Svi Mykhailiuk while putting up a shot.
He calmly drained all of them, and Devonte Graham's long 3 at the buzzer bounced harmlessly off the rim as the Horned Frogs leaped off their benched to celebrate a massive upset of the No. 1 seed.
They'll play No. 23
Kenrich Williams had 13 points, Robinson had 13 and Brandon Parrish had 12 for the Horned Frogs, who caught a break when Jayhawks Coach Bill Self suspended Josh Jackson for the game.
Jackson was cited for traffic violations in the latest incident involving the star freshman.
It was the second time the sixth-seeded Wildcats (20-12) have beaten the Bears (25-7) this season, giving them precisely the kind of marquee victory that the selection committee favors.
They'll get a chance for another against No. 11
No. 23 Iowa State 92, Oklahoma State 83: Monte Morris was an assist shy of the second triple-double in Big 12 tournament history, leading Cyclones to the win. Morris finished with 21 points, 10 rebounds and nine assists for fourth-seeded Iowa State (21-10).
Juwan Evans poured in 29 points as he tried to keep the Cowboys (21-11) afloat. But except for his backcourt mate Jeffrey Carroll, who had 21 points, the sophomore guard didn't get much help. The result was the fifth-seeded Cowboys' 10th straight loss to the Cyclones.
No. 11 West Virginia 63, Texas 53: Jevon Carter scored 21 points while the Mountaineers cranked up their trademark defense to cruise into the conference semifinals, where they will play ninth-ranked Baylor or Kansas State.
Second-seeded West Virginia (25-7) forced the Longhorns (11-22) into 14 turnovers, held them scoreless for the final 5:34 of the game and turned freshman forward Jarrett Allen into a non-factor on offense.
No. 14 Duke 81, No. 10 Louisville 77: Jayson Tatum scored 25 points and Grayson Allen provided an emotional lift during a second-half comeback to help the Blue Devils to victory. Deng Adel scored 21 points for Louisville (24-8).
No. 16 Florida State 74,
Seton Hall 82,