After Chris Rushworth had starred with four wickets to bowl the Hove side out for 105, putting the Dynamos in control at the halfway stage, Mike Yardy’s and Chris Nash’s spin wreaked havoc.
Durham were going well at 67-2 in the eleventh over, but quickly slipped to 78 all out in the 16th over on a slow and low turner.
Nash finished with 4-10 from 3.4 overs and former England one-day international Yardy 3-11 from four as Durham lost seven wickets for just nine runs in 31 balls.
Ben Stokes top-scored with 26 off 18 balls, but nobody else bettered Phil Mustard’s 15. They will now play the Fly Emirates XI in the plate final later this morning, UK time.
Earlier, Rushworth, the 25 year-old seamer, had adapted well to the slow and low conditions at the Sevens Complex to bowl Nash, Amjad Khan and Jimmy Anyon as well as getting Andrew Hodd caught.
The Hove outfit, quarter-finalists in last summer’s Friends Life t20 along with the Dynamos, struggled to recover from 24-3 after five overs, two of which were taken by Rushworth in a dangerous new ball burst with Graham Onions.
Onions also finished with 2-15 from four overs, while Mitch Claydon added 2-14 from three. England leg-spinner Scott Borthwick also struck.
Rushworth, whose figures of 4-14 were actually his best for Durham despite this only being a friendly, said: “To pick up a few wickets was a bonus for me.
“It’s very slow and low out there, and there’s not much bounce. I was trying to hit the stumps as much as possible with a lot of slower balls in there too.”