Brandon Hagel scored twice, Alex DeBrincat had a goal and an assist, and Kevin Lankinen made 32 saves for Chicago (21-30-8), which has lost seven of 10.
"It [stinks]," DeBrincat said. "I thought we played pretty well the whole game. Played for each other. It just didn't work out in the end. Their power play was good, and we kind of blew a couple chances on the power play."
Charlie Coyle put the Bruins ahead 1-0 at 4:12 of the first period with a wrist shot from the left face-off dot. He scored on a rebound after Lankinen made the save on Connor Clifton's shot from the slot.
DeBrincat tied it 1-1 at 6:41 with a one-timer off a pass from Kane on a 4-on-1. With the assist, Kane tied Bobby Hull for second on the Blackhawks points list with 1,153. Kane has scored 12 points (three goals, nine assists) in the past five games; he scored six (one goal, five assists) in an 8-3 win against the Anaheim Ducks on Tuesday.
"It's every game, where he's passed somebody. I can't keep up," Chicago coach Derek King said. "Like I've said before, he's a special player and a special person. With him being this hot right now, it's a good thing. We just need him to continue to stay hot."
Hagel gave Chicago a 2-1 lead at 4:12 of the second period with a wraparound off the rush after Boston turned it over in the neutral zone.
Ahcan tied it 2-2 on the power play at 11:57 with a wrist shot from the slot. It was his fifth NHL game.
"I think my mom's probably texting me now to see where I'm going to put [the puck]," Ahcan said. "She'll probably get it, so it's kind of cool for her. It's just such a good feeling. You know, you picture it over and over in your head before it actually happens. I don't think once it was like that, but it was a pretty awesome goal, and nice to get out of the way."