Talk:Heck reaction

More mechanism picture problems?
The oxidative addition should give the cis Pd(II) complex. Trans products from OA are only observed in stepwise mechanisms where there is a highly polarized C-X bond.

136.152.210.36 (talk) 00:55, 13 April 2009 (UTC)

I'm pretty sure you will get the trans product; in fact Heck reactions are remarkable in their trans selectivity. You will have rotation so Pd and H are coplanar for the beta-hydride elimination, but it will be in a way that both big groups are anti to each other - thus leading preferably to the trans product.


 * same question three times over: product formed has dangling bond, no preference for cis or trans implied V8rik (talk) 19:40, 30 April 2009 (UTC)

Mechanism picture incorrect?
The picture in the mechanism shows a cis product forming, when it should be a trans product.
 * Yes, you're correct. Someone needs to make a new image. ~K 17:18, 4 September 2006 (UTC)


 * the product now shows a dangling bond, issue solved V8rik (talk) 19:37, 30 April 2009 (UTC)

Reagents
It should also be stressed that this is the classic Heck cycle. New reports in the literature have modifications in which the catalytic species is an ionic palladium species in equilibrium with dimers or trimers. Look for works by De Vries on this topic.

Also the list of reagents and catalyst pre-cursors is greatly restricted. In fact almost every form of palladium imaginable has been tried as a Heck catalyst in a wide range of solvents and with a large variety of bases.

Also some names of chemicals used are out-dated. —Preceding unsigned comment added by 89.127.164.250 (talk) 19:16, 30 April 2009 (UTC)

BmimPF6 or BF4
Under the section, ionic liquid heck reaction, it mentions bmimBF6. Could someone clarify? --Rifleman 82 17:13, 23 January 2007 (UTC)

another source
http://www.organic-chemistry.org/namedreactions/heck-reaction.shtm

why isn't this artcle listed with the other organic chemistry article?129.49.7.125 19:01, 16 April 2007 (UTC)WoaT

Richard F. Heck

 * --Stone (talk) 20:05, 15 March 2008 (UTC)

More mechanism issues
Oxidative addition is generally presented as giving a cis product with respect to the carbon and halide ligands now attached to the metal center. I think the scheme should be changed to reflect that. My understanding is that trans products can be found in stepwise OA mechanisms which are generally only operational on strongly polarized C-X bonds. —Preceding unsigned comment added by 136.152.210.36 (talk) 00:45, 13 April 2009 (UTC)


 * product formed has dangling bond, no preference for cis or trans implied V8rik (talk) 19:38, 30 April 2009 (UTC)

Bumping this. I believe that this person and also the person who posted right at the top of this page are referring to intermediate 2 and not the final product. It is also my understanding, that aryl and bromide should be cis in the intermediate immediately following the oxidative addition of Ar-Br. The image of the catalytic cycle clearly implies trans which in turn would require a stepwise (and not concerted) mechanism of the oxidative addition. Note that this is entirely unrelated to the double bond symmetry of the final product. (Also, has the picture been modified since 2009? The picture I can see clearly creates the trans-alkene. Which is completely in agreement with the article's text.) – 193.175.244.3 (talk) 13:47, 27 January 2014 (UTC)