We were having some kitchen cabinets installed and the drain pipe the goes into the wall for the sink broke off, well part of the threads broke off inside the 45 deg. Connector inside the wall.

I can see the 45 deg connector and it looks fine and so does the pipe inside the wall, we removed the window sill for another reason so I can also see the connector and wall pipe from above.

The problem is most of the threads from the old nipple are still in the 45 deg connector. I have tried steel wool & a wire brush but I am getting nowhere. It's a 1.5 inch line.

What are my options? I can break more of the plaster to get to the 45 degree connector to remove it but I am unsure of the other pipe's threads and would prefer to leave it connected since the house is 50 years old. The wall pipe seems to be holding up to the scraping and brushing I was giving the connector. And the connector looks solid.

Do they make taps for 1.5 inch pipe?
Would it be best to break the plaster and replace the 45 connector?
Is there some sort of magic lube I can buy?

Thanks in advance and I apologize if the terminology isn't correct.

When threads break off I take a small, (very small) sharp chisel and carefully tap the chisel under the threads. You might mess up one thead doing it but teflon tape will seal the rest of the threads. When I get my chisel under one of the broken threads I pry it up and peel the rest of them out. After you remove the broken threads you can screw a PVC male threaded compression fitting in the 45 and convert to PVC the rest of the way. Good luck, Tom