[asa029]

I am going back to some synthetic problems I worked on a few years ago and wondered if anyone had any experience on this.

I've made a 4-(5)-alkynylated imidazole and want to hydrogenate the alkyne-moity. Traditional Pd/C and hydrogen gas (supplied from a baloon, festive!) did nothing, even on reflux for a day (re-supplying the baloon). Lindlar with very small amounts of added quinoline did not touch the alkyne either.

Anyone else tried similar things with other reagents/catalyst? Do I have to bring in the heavy artillary (platium metals) or heavy pressures?

[Doc Oc]

My personal experience with Pd/C is that it can be very finicky and goes bad rather quickly.  If you didn't have a relatively new bottle, the catalyst might be dead.  You can try increasing the catalyst load, but I always had great success with Pd(OH)₂ and a H₂ balloon for a variety of hydrogenations (deprotections, reductions, etc).