Showing posts with label organic synthesis. Show all posts
Showing posts with label organic synthesis. Show all posts

Saturday, June 20, 2015

The Old Days at Org Syn

Thanks to a bevy of used book stores, I'm slowly completing my collection of Profiles, Pathways, and Dreams, the biographical essay series from editor Jeff Seeman. I recently re-read four of these: Cheves Walling, F.G. Stone, Raymond Lemieux, and the indomitable Jack Roberts' colorful collection of biographical anecdotes. Never one to pull a punch, Roberts wistfully recalls his first involvement with Organic Syntheses in the mid-1950s, then led by famous organic chemist Roger Adams:
"The modus operandi of Organic Syntheses is relatively simple. Much of the work is carried on by mail, and the editors meet twice a year for much of a day to assign preparations, work out difficulties, plan for future volumes, choose new editors, and the like, with the current editor-in-chief presiding. Following that meeting, the editors join with the editorial board for cocktails and dinner at one of the best (and most expensive) restaurants in town. In the old days, the dinner would be followed by . . .an Adams report on whatever was on his mind at the time. He often ribbed his colleagues, without malice, but nonetheless, severely. After Adams finished, the meetings often degenerated into the semblance of a stag smoker, with rounds of off-color jokes, the most tasteless of which usually came from the representatives of the publisher . . .Rather prodigious quantities of spirits, wines, and brandies were consumed, and some of organic chemistry's most renowned practitioners had to be helped off the scene. My first encounter with these bacchanalian festivities was in Atlantic City, in the spring of 1956. I made it back to my hotel under my own steam, but I spent the next day in bed, a lesson I did not forget."

This recollection sounds uncomfortably close to how I felt each time someone in my graduate group passed their oral examinations. Some things never change.

Tuesday, May 19, 2015

Buried Treasure

Regular readers know that I've been collecting names of chemistry faculty moves for a while now. I had to chuckle at this particular announcement, by friend of the blog (and fellow Tweeter) Prof. Karl Gademann. From two clicks deep on his group's home page:
"Prof. Gademann's first professorial appointment was at the EPFL in Lausanne, and he currently holds a chair at the University of Basel as a full professor. He has been elected to the board of the Swiss Academy of Sciences, and is affiliated to the National Centres of Competence in Research ‘Chemical Biology’ and ‘Molecular Systems Engineering’. Karl Gademann will move in Summer 2015 to the University of Zürich. His work has been recognized by a number of international awards, including the Latsis prize, the Novartis Early Career Award, the Ruzicka Medal, The Liebig Lecture by the German Chemical Society, and the European Young Investigator Award."
Thanks to an eagle-eyed commenter for the link.

Also, from both sites (UZH, BAS), it would appear that Dr. Gademann looks most professional when posed behind a rotovap condenser.

Best of luck in the new position, Karl - we'll add you to the list!

Thursday, June 13, 2013

Friday Fun: Thulium Breaks 'Em Down

Seriously, how often do you see thulium in the chemistry mainstream?

Prof. David Procter and Dr. Michael Szostak, of U. Manchester in England, want you to think of it a lot more often. Their latest ACIEE explores some crazy stunts thulium diiodide can do when mixed with a little alcohol: Blowing apart esters. Reducing arenes. Unwrapping amides (see below):


All thanks to the extra reducing power of this "non-classical" lanthanide salt. At a good 50% more than samarium diiodide, thulium diiodide can inject a single electron into just about any C=O or arene around, and there's evidence that it slips into neighboring C-N bonds to promote fragmentation:

Source: Szostak, ACIEE 2013

Bill Evans (organometallics, not jazz) previously explored this reagent over a decade ago, marketing it as a souped-up SmI2 / HMPA. His study looked at cyclic ketones, which formed adducts with primary iodides in less than a minute with a healthy dose of TmI2(DME). Despite these exciting early results, it appears that thulium took a back burner to the samarium 'craze' of the mid-'00s, and only now gets its chance in the limelight.

Keep an eye out for more TmI2 reactions; after 100 years of new bond-forming reactions, it's nice to see trends to the contrary.

Happy Friday,
SAO

Update (6/14/13) - Added Prof. Procter and group website. 
(6/14/13) - Changed lactam to amide - thanks, Anon!

Wednesday, December 12, 2012

The Sweet Science

Hello, amine equivalent!
Source: Cumberland Packing Grp.
No, not boxing . . .chemistry!

From a fresh Org. Lett. ASAP, courtesy of the Amgen Process group, comes the 2-amination of some 3,5-disubstituted pyridine N-oxides. The group wants to add in an ammonia surrogate, but faces low conversions and poor regioselectivities (2- vs. 6-) with "standard" literature conditions (excess tert-butylamine, tosic anhydride). Substantial gains occur with a switch to Hunig's base and TsCl, but they need to find a bulky, electron-poor nitrogen source. Since we're potentially talking kilos here, price and availability become major considerations.

So what did the researchers choose as their "N" source? Saccharin. Yup, the artificial sweetener from the pink packets, used on process scale. Saccharin beat out many other "Gabriel-type" protected amines (phthalimide, Boc phosphoramidate, etc.), and you can't beat the price: about $5 / kilo. Under optimized conditions, the group saw yields from 21-97%, and product ratios of ~28:1. Better still, acidic hydrolysis (HCl, 80 degrees) frees up the 2-aminopyridine compounds, most of which are crystalline solids.

Pretty sweet synthesis.