[prozen]

I've done a very similar reaction to the one below but by TLC I observe only starting materials. It's super clear that nothing else is going on. Conditions: K3PO4, Pd(dppf)Cl2, dioxane/water, heat to 100 deg.C.



What thoughts do you have on why this doesn't work?

1.) I imagine the alkyne chelating to the Pd and potentially 'poisoning' it? I currently lack the words and technical lingo to put this into a formal explanation.

2.) A competing sonogashira perhaps? Unlikely given the aqueous conditions.

3.) Any other issues?

[Dan]

Terminal alkynes are often problematic, can you make a silyl-protected version?

[prozen]

Terminal alkynes are often problematic, can you make a silyl-protected version?

Hi, My issue is not so much about getting this to work.

My real question is WHY do terminal alkynes cause an issue? What is the fundametal issue they pose in a suzuki like this?

[wildfyr]

Acidic proton?

[Dan]

Terminal alkynes are often problematic, can you make a silyl-protected version?

Hi, My issue is not so much about getting this to work.

My real question is WHY do terminal alkynes cause an issue? What is the fundametal issue they pose in a suzuki like this?

Terminal alkynes are quite acidic and the resulting alkynide is a good ligand for a lot of transition metals. This means you can expect the alkyne to coordinate to the catalyst, which may result in side reactions and/or deactivation. Consider also that alkynes can tautomerise under basic conditions (via alkynides), which may open up some non-productive pathways.