Kilmarnock suffered penalty heartbreak thanks to Hibernian's 5-4 win on spot-kicks.
Niko Hamalainen and Stephen O'Donnell missed from the spot to send the Hibees through.
Stephen O’Donnell tested Chris Maxwell in the opening minutes but his effort was palmed out for a corner.
Both sides struggled to create chances until the 24th minute when some good work from Christian Doidge ended in a Stevie Mallon shot, but it fell wide of the target.
In the 40th minute Dario Del Fabro had a half chance as the Killie centre-back fired a header over the crossbar.
Killie had penalty shouts thrown out by whistler Willie Collum just before and just after half-time.
Eamonn Brophy went down just before the break, and the Scotland cap was involved again after the break as he flick up appeared to be handled by the Hibs defence, but Collum waved play on on both occasions.
Harvey St Clair almost incredibly eluded Maxwell with a cross that was close to dipping into the net.
Chris Burke was the first into Collum’s book as he flew into a tackle on Josh Vela and saw yellow.
Liam Millar came off the bench and looked to make an instant impact as he made a bursting run down the wing in the 66th minute, but his effort ballooned over and wide after he cut inside.
Oli Shaw had a decent chance in the 71st minute when he met a Tom James corner, but his header was well tipped over by Laurentiu Branescu.
In the 80th minute Brophy had a great chance after Maxwell slipped, but he sailed his effort over the crossbar.
Millar was hauled down in the area minutes later but again Collum said no to a penalty.
Dom Thomas smashed the inside of the post at the beginning of the second-half of extra-time.
Ryan Porteuous was shown red for a cynical foul on Liam Millar in the closing minutes.
