Gas B vent fireplace venting option ? help

cvcman

Can a B vent fireplace that vents off the top go into a 90 then out thru the wall then run at a 45 deg angle to a chimney then go straight up the chimney ?? Or is there a way to go at a 45 off the top of the unit thru a wall thimble and continue at an angle to the chimney ?? Do they make a 45 wall thimble ??