Reactions dearomatization

Osmium- and Rhenium-Mediated Dearomatization Reactions with Arenes... 

Anisole and its derivatives have thus far demonstrated the widest variety of [Os]-mediated dearomatization reactions. These transformations have included substitutions, asymmetric tandem addition sequences, and a variety of cyclizations. 

A. R. Pape, K.P. Kaliappan, and E. P. Kiindig, Transition-Metal-Mediated Dearomatization Reactions, Chem. Rev. 100, 2917-2940 (2000). 

McComas, C. C., Van Vranken, D. L. Application of chiral lithium amide bases to the thia-Sommelet dearomatization reaction. Tetrahedron Lett. 2003, 44, 8203-8205. 

The second mesopore form is connected to zeolite dealumination in the Mo presence during the dearomatization reaction and followed by the formation of... 

Arenes and aromatic heterocycles are widely available. They are readily deri-vatized through electrophilic and nucleophilic substitution, or via ortho-lithia-tion followed by reaction with electrophiles (see also Chap. 3). Routes to differentially substituted aromatic products are thus well established. This is not the case for substitutive dearomatization reactions, primarily because this requires disruption of the aromatic n system. Benzene and its derivatives are attractive starting materials because they have the potential to provide a rapid entry into complex alicyclic synthetic building blocks containing unmasked functionality, new carbon-carbon bonds, and new stereogenic centers [ 1 ]. 

It can be expected that arene metal chemistry will find many more applications in natural product synthesis in the future. Besides the (stereo-) selective functionalization of aromatic compounds, methods involving dearomatization reactions [4] possess a particular and not yet fully exploited potential. 

What follows is a description of the trials and tribulations we experienced during our development of a short synthetic route to sorbicillactone a target that Porco has described as a deceptively simple molecule. To be clear, this work led to the synthesis of racemic material. Our group does have a strong interest in developing aryl iodide catalysts for asymmetric oxidative dearomatization reactions, and we have made some progress in this area. However, this has proved to be a very challenging area of research and still requires a fair amount of development. ... 

There were hints in the literature that certain silylated phenols were more efficient substrates than free phenols in hypervalent iodine-mediated oxidative dearomatization reactions." The mechanistic underpinnings for this observation are still murky. Nevertheless, when phenol 40 was first converted into the corresponding trimethylsilyl ether and then treated with PhI(OAc)2 in acetonitrile-water, the desired quinol (42) was formed with improved yields (77-95%) and on larger scale (>1 g) (Scheme 16B). The conditions used to... 

In 2009, Buchwald and co-workers reported the first asymmetric palladium-catalyzed intramolecular dearomatization reaction. Benzo-carbazole derivatives were obtained in high yields and enantioselectivities from naphthalene derivatives (Scheme 2.122). Here, it is important to note that dearomatization of arenes is recognized as a fundamental chemical transformation for organic chemists which allows efficient access to alicyclic frameworks present in many biologically active compounds. 

---