Altered States - C-H Borylation

Reference:
Iridium-Mediated Borylation of Benzylic C H Bonds by Borohydride, Christina Y. Tang, William Smith, Amber L. Thompson, Dragoslav Vidovic, and Simon Aldridge
Angew. Chem. Int. Ed.

A nice achievement in the field of C-H Borylation. The interesting aspect is the use of a borohydride (BH4-) as the ‘boryl’ source. The group has also proposed an intriguing mechanism to rationalize the selective borylation of the benzylic C-H bond. The methyl C-H bond is activated by the iridium catalyst, and is then followed by delivering the ‘boryl’ moiety to this particular C-H bond. This ‘closed’ reactive intermediate should explain the great selectivity of the borylation reaction. This is great work because further developments will surely expand the scope of reagents used for borylating organic substrates in synthesis.

Yet Another C-H Activation - in Organic Synthesis

Reference: To, C.T., Chan, T.L., Li, B.Z., Hui, Y.Y., Kwok, T.Y., Lam, S.Y., Chan, K.S., C-H Arylation of Unactivated Arenes with Aryl Halides Catalyzed by Cobalt Porphyrin, Tetrahedron Letters (2010)

Professor Chan's work is impressive. It represents yet another scrupulous use of C-H activation in organic synthesis, this time using Cobalt as the catalyst. This coupling reaction enables an unactivated aromatic (benzene) to be stitched onto a functionalized aryl halide, and the result is an arylation to form useful biaryls. As they have suggested, this prevents the use of hard reagents such as Grignards and organolithiums in the reaction.

A personal observation: we can see from a number of recent publications that Cobalt is emerging as a good metal for a number of useful organic transformations, especially coupling reactions. Watch out, Copper!

Queen B's Badge

http://www.economist.com/blogs/babbage/2010/12/bee_biology

Bee Molecular Biology - see how the action of methylation (adding methyl 'CH3' groups) gives rise to intriguing differences for queen B and worker bees. This is something interesting from the emerging field of 'Epigenetics'.

Epigenetic anointment
Dec 23rd 2010 The Economist

Catalyst Barred

Unusual deactivation in the asymmetric hydrogenation of itaconic acid
T. Schmidta, W. Baumanna, H.-J. Drexlera and D. Heller
Journal of Organometallic Chemistry, Article in Press, Accepted Manuscript

This article is important. Given that itaconic acid is biologically significant and is a precursor to many other biological compounds, and Rh-catalyzed hydrogenations are so important for asymmetric synthesis. The understanding of how this deactivation pathway for the catalyst will serve as important insights for future preparations of the useful enantiomeric compounds.

Link:

http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6TGW-51S6XJF-3&_user=121739&_coverDate=12/22/2010&_rdoc=1&_fmt=high&_orig=browse&_origin=browse&_zone=rslt_list_item&_srch=doc-info(%23toc%235265%239999%23999999999%2399999%23FLA%23display%23Articles)&_cdi=5265&_sort=d&_docanchor=&_ct=182&_acct=C000010018&_version=1&_urlVersion=0&_userid=121739&md5=22108964a831ee2923a23f9f75304b55&searchtype=a

Molecular Lego - Again!!

A great methodology for catalytic pyrrole synthesis by the Master of Atom Economy, Prof. Trost. This method can lead to useful pyrrole derivatives. The 'Molecular Lego'-style chemistry will prove to be important foe better and more efficient syntheses.

*Diagram from J. Am. Chem. Soc. Webpage

Reference:
An Atom-Economic Synthesis of Nitrogen Heterocycles from Alkynes
Barry M. Trost*, Jean-Philip Lumb, and Joseph M. Azzarelli
J. Am. Chem. Soc., Article ASAP

Cutting edge chemistry in 2010 - Article from RSC Chemistry World Magazine

http://www.rsc.org/chemistryworld/News/2010/December/21121001.asp

C-H Activation of Alkanes in Organic Synthesis - Aromatic synthesis

What an achievement in catalysis. These workers are using the inert alkanes as starting materials, and convert them into aromatic compounds under iridium catalysis - an atom-economical dehydrogenative reaction. This sets a standard for the kind of chemistry we want in an era after ‘cross-coupling chemistry are awarded a Nobel prize’ : C-H Activation of the most unreactive substrates to give useful chemical compounds.

*Diagrams above from Nature Chemistry and http://www.rsc.org/chemistryworld/News/2010/December/19121001.asp

Catalytic dehydroaromatization of n-alkanes by pincer-ligated iridium complexes
Ritu Ahuja, Benudhar Punji, Michael Findlater, Carolyn Supplee, William Schinski, Maurice Brookhart & Alan S. Goldman, NATURE CHEMISTRY

http://www.nature.com.eproxy1.lib.hku.hk/nchem/journal/vaop/ncurrent/abs/nchem.946.html

This achievment is covered in RSC Chemistry World Magazine

http://www.rsc.org/chemistryworld/News/2010/December/19121001.asp