Better Than Word of Mouth

Hello, dear readers. It's been...a while. I promise the blog is not dead, just sleeping for now. My 2017 New Year's resolutions include sculpting specific time out for all the sci-writing goodness. Stay tuned.

Enough maudlin overtures. Now, on to the fun!

Strem has, as any synthetic guru would attest, the highest-quality metal precursors in the biz.* Now, you could spend a weekend cracking ampoules to find out, or just open to the Supporting Information of one of Jeff Bode's recent publications in Org. Lett. Perhaps you remember this reaction - SnAP synthesis of saturated heterocycles - best from a cheeky Derek Lowe tweet:

That's in reference to the stoichiometric incorporation of tin** in the reagent, which serves as a linchpin for the eventual transmetalation to a copper species and ring closure, neatly without disturbance of the ipso heteroatomic group.

Well, much to my surprise, Prof. Bode has climbed on the recent trend of showing one's work through tactful inclusion of smartphone pics to buoy up procedure adoption. Especially with fussy transition metals, valency, contaminants, poor environment, and a whole host of other factors lead to catalyst poisoning and color changes. In the SnAP case, the litmus test seems to be formation of a correctly ligated Cu(II) ion in lutidine relative to the (probable) hexaaquo cuprate species formed as a blue heterogeneous train wreck.

The kicker? The fairly indiscreet preference for the Strem copper(II) precursor over all other suppliers. Look at the change! Night and day, and key to making these reactions work.

You couldn't buy better advertising than this....right, Strem?
Bravo, Bode group! I look forward to seeing your colorful coupling chemistry in future reads.

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*Dear Strem: please send non-sequential $50 bills to See Arr Oh at Big City Company, USA
**SnAP. Get it? [drum kit]

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?