How do you make propoxyphene?

Answer 1

According to a patent awarded to Mallinckrodt in 1987, you start with propionyl chloride and alpha-d-1,2-diphenyl-3-methyl-4-dimethylamino-2-butanol and use a small amount of thionyl chloride to improve yield.

That's going to be totally useless to you, which is why I bothered to answer. Propoxyphene is illegal.

It's also lame. If you're going to make illegal opioids, you might as well go for one of the good ones like morphine or hydrocodone, not a weak painkiller that's also pretty toxic.