Monday, March 16, 2015

Acylboronates Enter the Mix?

Just a few days removed from the great Synthesis Machine debate of '15, a new paper has appeared that prompts me to wonder: might other protected boronates work in this chemistry?

The Bode group, now at ETH-Zurich, discloses in JACS ASAPs some intriguing bifunctional acylboronates. Much like their MIDA boronate cousins, these, too, are stabilized by an N,O-chelating ligand, demonstrate a shelf-life of several months, and are easily prepared in one step from their potassium trifluoroborate salts.

Do you suppose these reagents could survive the strongly basic aqueous conditions used for MIDA deprotection and subsequent cross-coupling? The authors, comparing MIDA-acylboronates against NOF-acylboronates under aqueous hydrolysis conditions, claim:
"In all cases, the bidentate, monofluoroacylboronates were much more stable than the MIDA variants and should be sufficiently stable* for most applications." 
If this holds true, one could imagine capping Burke's automated syntheses with carboxylic acid derivatives without resorting to bulky t-Bu esters or exotic silyl-protected esters.

*Now I'm just brainstorming, but could catalytic conditions be found to transmetalate the acylboronate to, say, Rh or Pt? 

1 comment:

  1. This one definitely makes me go "Oooooh." Interesting (albeit not too atom-economical) method for the synthesis of amides, too. My guess is they're busting their butts to figure out how to transmetalate the acyl group.