Plumbing and Piping - Threads full of gunk

Hi - I was replacing the bathroom sink and the drain pipe came off in my hand. The inside of the pipe (in the wall) is full of gunk and corrosion. I got a new 1-1/2" pipe, but I can't get it to thread into the pipe in the wall. I've tried cleaning it with a wire brush and still no go. They don't seem to sell any adapters that would connect the two (a 1-1/2" pipe into a pipe that's about 2-1/2" on the outside).

Are there any solvents that would get the crud out without dissolving the threads? If not, any suggestions about how to proceed?

The reason the pipe came off in my hand is that the last person who faced this same problem just stuck the pipes up against each other, applied putty, and ran for his life!

Thanks for any help.

Chessie

Do you see any existing threads still in the pipe in the wall, if there is, this is stopping you from installing the new nipple, if no thread, what I have done in the past is, get and attach a wheel wired brush to a drill, just smaller then the inside of the threded fitting in the wall, clean it real good, and see if it starts afterwards.