Platinum wonders

This is impressive. Not only have they successfully made the fascinating (and elusive?) Pt (IV) complexes, their investigations also led us to a number of thought-provoking questions. First, can a Pd (II) / Pd (IV) parallel be drawn - this will definitely become useful insights to synthetic chemists. The system they have been using to achieve this is an interesting one - a pyridine linked to a fluorobenzene. The ortho hydrogen to the pyridine ring that has shown some intriguing interactions to the platinum centre. Thus if we modify the substituent group on the benzene to other types of functionality (e.g. EDG), the impact it will impart on this 'reactive hydrogen' is also worth looking at. This kind of makes sense because the authors have noted torsional effects on the phenyl-pyridine ring towards the energy profile. Of course, the alkyl group on the pyridine - which is where all the agostic interactions originate and the key to the formation of the Pt (IV) centre. It will also be great to see what will happen if we impart some form of restrictions to this side chains (e.g. installation of t-butyl group or a more complicated side chain) and probe the differences it will cause to the formation of the Pt(IV) centres. Overall, a very useful investigation.


Reference:
Platinum(IV) centres with agostic interactions from either sp2 or sp3 C–H bonds Sarah H. Crosby, Robert J. Deeth, Guy J. Clarkson and Jonathan P. Rourke
Dalton Trans., 2011, Advance Article
DOI: 10.1039/C0DT01428A

Textbook reaction with a twist

A nice demonstration of the classic 'synthetic logic' of heterocycles. This author makes useful imidazole derivatives with Zinc Triflate as the catalyst.

Reference:
A novel Zn-catalyzed hydroamination of propargylamides: a general synthesis of di- and tri-substituted imidazoles

Anahit Pews-Davtyan and Matthias Beller
Chem. Commun., 2011, Advance Article

DOI: 10.1039/C0CC04625F

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