Comments on: Boron Meltdown http://www.coronene.com/blog/?p=630 A chemistry blog about organic materials, nanocrap, life in the lab and kittens Fri, 10 Sep 2010 22:53:55 +0000 http://wordpress.org/?v=2.9 hourly 1 By: JH http://www.coronene.com/blog/?p=630&cpage=1#comment-6126 JH Wed, 18 Feb 2009 19:43:00 +0000 http://www.coronene.com/blog/?p=630#comment-6126 So the issue was the one I suspected. I shall keep this info in mind, thank you very much. So the issue was the one I suspected. I shall keep this info in mind, thank you very much.

]]> By: Chip http://www.coronene.com/blog/?p=630&cpage=1#comment-6121 Chip Wed, 18 Feb 2009 11:47:19 +0000 http://www.coronene.com/blog/?p=630#comment-6121 Same thing in Mexico. I guess I'll have to wait until I get home to view it. Same thing in Mexico. I guess I’ll have to wait until I get home to view it.

]]> By: milkshake http://www.coronene.com/blog/?p=630&cpage=1#comment-6116 milkshake Tue, 17 Feb 2009 21:38:24 +0000 http://www.coronene.com/blog/?p=630#comment-6116 It is my experience that Sonogashira with aryl brodies using Pd(II) does not start until you throw in Cu(I) salt. The right procedure is to mix PdCl2(dppf) 3 mol% with ArBr and 1-alkyne 1.2 eq and NEt3 1.5 eq in fresh THF, Ar sparge on ultrasound for few minutes and THEN throw in CuI or CuBr 1.5 mol% solid and cap the vial. The color promptly changes from red to gray to gold yellow within minutes at room temp, later NEt3.HBr begins to precipitate out. but the color stays yellow until the quench. I think Cu-acetylide is the actual Pd-reducing agent. NEt3 can also reduce Pd(II) but you need reflux temperature and long reaction time - and your alkyne is likely to perish by the Pd(II) long before it gets a chance for a sonofashira It is my experience that Sonogashira with aryl brodies using Pd(II) does not start until you throw in Cu(I) salt. The right procedure is to mix PdCl2(dppf) 3 mol% with ArBr and 1-alkyne 1.2 eq and NEt3 1.5 eq in fresh THF, Ar sparge on ultrasound for few minutes and THEN throw in CuI or CuBr 1.5 mol% solid and cap the vial. The color promptly changes from red to gray to gold yellow within minutes at room temp, later NEt3.HBr begins to precipitate out. but the color stays yellow until the quench. I think Cu-acetylide is the actual Pd-reducing agent. NEt3 can also reduce Pd(II) but you need reflux temperature and long reaction time – and your alkyne is likely to perish by the Pd(II) long before it gets a chance for a sonofashira

]]> By: excimer http://www.coronene.com/blog/?p=630&cpage=1#comment-6115 excimer Tue, 17 Feb 2009 18:30:38 +0000 http://www.coronene.com/blog/?p=630#comment-6115 Any catalyst BUT PdCl2(PPh3)2 works great, especially if you use a hot ligand like PtBu3 or a Buchwald ligand with a good Pd(0) source (most commonly used is allylpalladium chloride dimer-Pd2dba3 doesn't work as well). I do this coupling via "soft" deprotonation with ZnBr2/NEt3 all the time and I get quantitative yields (nearly) every time. It doesn't work with Pd(II) sources cause there's no way to get down to Pd(0) when you use zinc halides (zinc acetylides don't homocouple). Any catalyst BUT PdCl2(PPh3)2 works great, especially if you use a hot ligand like PtBu3 or a Buchwald ligand with a good Pd(0) source (most commonly used is allylpalladium chloride dimer-Pd2dba3 doesn’t work as well). I do this coupling via “soft” deprotonation with ZnBr2/NEt3 all the time and I get quantitative yields (nearly) every time. It doesn’t work with Pd(II) sources cause there’s no way to get down to Pd(0) when you use zinc halides (zinc acetylides don’t homocouple).

]]> By: JH http://www.coronene.com/blog/?p=630&cpage=1#comment-6114 JH Tue, 17 Feb 2009 18:26:07 +0000 http://www.coronene.com/blog/?p=630#comment-6114 It's funny how palladium chemistry review articles etc written by Negishi make a great point about the superiority of Negishi coupling compared with Sonogashira, particularly when it comes to yields. It must piss him off that the more popular alkyne coupling doesn't bear his name. Also his alkyne coupling with ZnBr2 and tertiary amine (which btw didn't give a clear solution like they were supposed to) never gave me the results they touted. Then again it was with Pd(PPh3)2Cl2. Maybe Pd(PPh3)4 would have worked, never tried. It’s funny how palladium chemistry review articles etc written by Negishi make a great point about the superiority of Negishi coupling compared with Sonogashira, particularly when it comes to yields. It must piss him off that the more popular alkyne coupling doesn’t bear his name. Also his alkyne coupling with ZnBr2 and tertiary amine (which btw didn’t give a clear solution like they were supposed to) never gave me the results they touted. Then again it was with Pd(PPh3)2Cl2. Maybe Pd(PPh3)4 would have worked, never tried.

]]> By: nicolaou... secrets http://www.coronene.com/blog/?p=630&cpage=1#comment-6106 nicolaou... secrets Sun, 15 Feb 2009 18:28:44 +0000 http://www.coronene.com/blog/?p=630#comment-6106 Phil Baran is my son! Yes, a great shock! You didn't see that one coming, did you? ...you did? Oh. Never mind. Phil Baran is my son! Yes, a great shock! You didn’t see that one coming, did you?

…you did? Oh. Never mind.

]]> By: Will http://www.coronene.com/blog/?p=630&cpage=1#comment-6088 Will Fri, 13 Feb 2009 03:17:53 +0000 http://www.coronene.com/blog/?p=630#comment-6088 Wow, this made my day. He's amazing... Wow, this made my day. He’s amazing…

]]> By: excimer http://www.coronene.com/blog/?p=630&cpage=1#comment-6078 excimer Wed, 11 Feb 2009 19:58:28 +0000 http://www.coronene.com/blog/?p=630#comment-6078 Hello Purdue chemist! I, personally, have nothing against Negishi. He's about a 95%<sup>1</sup> great chemist. <sup>1</sup> Yields determined by GC Hello Purdue chemist! I, personally, have nothing against Negishi. He’s about a 95%1 great chemist.

1 Yields determined by GC

]]> By: yoyo http://www.coronene.com/blog/?p=630&cpage=1#comment-6077 yoyo Wed, 11 Feb 2009 19:16:29 +0000 http://www.coronene.com/blog/?p=630#comment-6077 what's your beef with negishi? you dimwitted newb what’s your beef with negishi?

you dimwitted newb

]]> By: Hap http://www.coronene.com/blog/?p=630&cpage=1#comment-6076 Hap Tue, 10 Feb 2009 21:56:29 +0000 http://www.coronene.com/blog/?p=630#comment-6076 Aren't lots of boranes pyrophoric? Karma could be a problem for the waterboarders. I don't consider that a problem, exactly, but there's no rinse and repeat cycle there. Aren’t lots of boranes pyrophoric? Karma could be a problem for the waterboarders. I don’t consider that a problem, exactly, but there’s no rinse and repeat cycle there.

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