You can't run 1 1/2" vent pipe through a 2 x 4. The support will be gone. You can run the pipe along the outside of the wall, under the counter/cabinet until you turn into the stud space you will vent up through (that's what I did when I put a big window in over my sink and had to re-locate the vent), OR use an island vent arrangement, see these links:

http://www.theplumber.com/vent.html
http://www.longbeach.gov/plan/helphome/IslandVent.html
http://www.doityourself.com/architecture/plumbingcodes.htm (scroll down till you find it)

If it were me, I would run a new vent through the roof and eliminate as much horizontal vent run as possible. Nothing says your kitchen vent has to tie into the bathroom vent (mine doesn't).