Nov 24, 2009

One reaction, three bonds

I was just catching up on some of the overnight publications and this one from Song and Dong in ACIE stuck out: Pd-catalysed intramolecular carboesterification of olefins.

A scheme will probably clear things up:

As the authors describe, what this Pd mediated transformation achieves is a formal [3+2] cycloaddition. It is certainly only a cycloaddition in a formal sense if one takes a look at the mechanism proposed by the authors (which I have no problems with). It's all pretty well established stuff (chloropalladation, reductive elimination etc) as well as based on mechanistic studies (that's the oxypalladation step). I've certainly seen Pd catalysed reaction mechanisms which... let's just say a great deal of Jedi mind tricks will be required for me to accept them.

A bit about the conditions: The catalyst loading is low (1%, no conversion without the presence of catalyst), in a polar solvent (acetic acid or MeCN). The highest yield observed on the model system (in the first scheme) was 83% using MeCN and 3eq of LiCl. Apparently the reaction is not air or moisture sensitive either which is great; using inert gas reaction atmosphere isn't that annoying, but drying and degassing solvents do take up time.

But there are two things I really like about this publication:

1. In one step you form three bonds. Fair enough, only one of them is a C-C bond (Diels-Alder is still king) but you do form two rings. And the C-Cl bond is awesome because...

2. ... the vinyl halide functionality of the product is primed for another Pd catalysed C-C forming reaction. I'm thinking Stille, Heck etc. Now I wonder if you can tweak it so that you can add a stannane in there and do a Stille in the same pot...


  1. very well spotted mate, that will be a nice one for some poor schmo down the line who has to synthesis some fused bike.

  2. Interesting post! I read about Pd-catalysed intramolecular carboesterification of olefins back in high school. I am a college sophomore (2nd year) with a dual major in Chemistry and Psychology @ Duke. By the way, i came across these excellent chemistry flash cards. Its also a great initiative by the FunnelBrain team. Amazing!!!

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