Sunday, March 24, 2013

Clip chemistry

Oxidation-Accelerated Hydrolysis of the Ortho Ester-Containing
Acid-Labile Polymers
Cheng-Cheng Song, Ran Ji, Fu-Sheng Du, De-Hai Liang, and Zi-Chen Li

An interesting example of "clip" chemistry: cleavage of 4-(pinacolboryl)-benzyl ester using H2O2, resulting in a carboxylic acid and p-quinone methide (which eventually undergoes hydration).

Speaking of Chromatography..

The presentation today on GPC and HPLC reminded me of a Baran Lab blog post I read not too long ago about moving bed chromatography and this paper specifically.
This type of chromatography was developed to better separate enantiomers by moving the stationary phase of a column in the opposite direction of the mobile phase as shown in the diagram below.
It's tough to move the stationary phase though without causing mixing and other problems and so they designed a simulated moving bed system. This is comprised of four sections of regular columns with various ports for feeding and extracting solvent in and out of. By rotating the ports at which you feed mobile phase into and extract products in the direction with the mobile phase flow, you simulate the solid moving in the opposite direction. This process is widely used in industry, the separation of fructose being a notable example.
Of course this requires tons of optimization which you can read about in that paper. 

C-H activation

Palladium(0)-Catalyzed Alkynylation of C(sp3)−H Bonds
Jian He, Masayuki Wasa, Kelvin S. L. Chan, and Jin-Quan Yu
An important transformation for building carbon skeletons. 
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C-H activation

Iridium-Catalyzed C–H Borylation of Cyclopropanes

Carl W. Liskey and John F. Hartwig

This reaction might allow easy synthesis of substrates poised for Suzuki cross-coupling.

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NHC complexes

NHC Ligands as Modulators of Luminescence in Three-
Coordinate Gold(I) Complexes with Spectacular Quantum Yields
Renso Visbal, Isaura Ospino, Jose Maria Lopez-De-Luzuriaga, Antonio Laguna, and M. ConcepciĆ³n Gimeno
Solution- and solid-state- stable three-coordinate gold complexes with NHC/carborane-diphosphine ligands have been prepared and they display very high quantum yield for phosphorescence.
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Gold complexes

A Golden Ring: Molecular Gold Carbido Complexes
Elliot S Borren, Anthony Francis Hill, Rong Shang, Manab Sharma, and Anthony Creswick Willis
This paper reports an interesting complex containing 4 gold atoms arranged in a ring spaced by single carbon atoms

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Efficient C-Ar bond formation

Nickel-Catalyzed Cross-Couplings of Benzylic Pivalates with Arylboroxines: Stereospecific Formation of Diarylalkanes and Triarylmethanes

Qi Zhou , Harathi D. Srinivas , Srimoyee Dasgupta , and Mary P. Watson *

"We have developed a stereospecific nickel-catalyzed cross-coupling of benzylic pivalates with arylboroxines. The success of this reaction relies on the use of Ni(cod)2 as the catalyst and NaOMe as a uniquely effective base. This reaction has broad scope with respect to the arylboroxine and benzylic pivalate, enabling the synthesis of a variety of diarylalkanes and triarylmethanes in good to excellent yields and ee’s."

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