Current Organic Chemistry - Volume 12, Issue 9, 2008

The Nenitzescu reaction is a classical methodology to quickly obtain highly functionalized indole derivatives. The reaction is now brought up-to-date by Drs Patil, Patil and Miller from the University of Tennessee, Memphis, USA. Bicyclic polyhydroxylated alkaloids constitutes an interesting and biologically active class of molecules. Stereochemical challenges are multipresent. All these aspects are attended by Prof. Lopez and her co-workers from the University of Jaen, Spain. The imino-pinacol coupling offers an attractive access to 1,2-diamines, which in turn have important applications in medicinal chemistry and asymmetric catalysis. This field is now reviewed by Prof. Genisson and Dr Faugeroux from Universite Paul Sabatier, Toulouse, France. The final contribution authored by Prof. R. Rossi and his co-workers from the University of Pisa, Italy, features recent denvelopment of arylheteroarenes and biheteroaryls.

A variety of natural and unnatural molecules containing a 5-hydroxyindole moiety have displayed strong pharmacological activities. In this context the Nenitzescu reaction has proven to be extremely useful for the preparation of 5- hydroxyindoles directly from simple and accessible materials like 1,4-benzoquinone and enamines. This review will summarize recent applications for the synthesis of complex 5-hydroxyindole derivatives such as pyrimido[4,5-b]indol-4- amines, 5H-benzo[b]carbazoles, 5'-hydroxynaltrindolomorphinans, and 3-[3-(amidomethyl)-2-ethyl-1-(phenylmethyl)- 1H-indol-5-yloxy]propylphosphonic acid (LY311727) which possess important biological activities. The Mechanism of the Nenitzescu reaction is discussed and as is recent utilization of solid phase chemistry to the Nenitzescu reaction.

This review deals with the latest developments in the synthesis of bicyclic iminosugars.

interest in imino-pinacol coupling arises from the access it offers to 1,2-diamines, a highly valuable class of compounds that have found constant applications in medicinal chemistry and asymmetric catalysis. The present paper intends to cover, from the 60's to present, the different chemical approaches applied to the imino-pinacol coupling, setting each procedure in an historical perspective and delineating general reactivity trends. This review shows that, even though the last 40 years has witnessed an impressive evolution, there is still room for improvement both in terms of flexibility and stereoselectivity.

The past decade has witnessed significant progress in highly regioselective direct arylation of azoles with aryl halides. This account aims to summarize recent progress in the development and application of these reactions. In particular, it describes and comments on the results obtained in the development of efficient protocols for the selective Pdcatalyzed direct C-5 arylation of 1-aryl-1H-imidazoles, 1-benzyl-1H-imidazole and 1-methyl-1H-imidazole and the highly regioselective Pd-catalyzed and Cu-mediated direct C-2 arylation of azoles, including free (NH)-imidazole, - benzimidazole and -indole. The utility of these novel protocols for the concise and efficient preparation of 1,5-diaryl- and 1,2-diaryl-1H-imidazoles, including derivatives of potential pharmacological interest, 4(5)-aryl-, 4,5-diaryl- and 4,5- diaryl-1-methyl-1H-imidazoles, 2-arylbenzothiazoles and 2-arylbenzimidazoles, including bioactive compounds or their precursors, and 2,4(5)-diaryl-1H-imidazoles is also disclosed. Finally, this account illustrates the results of an attempt to optimize a protocol for the direct C-2 arylation of 1H-indole, which enabled the development of a new, convenient and functional group-tolerant version of the Ullmann reaction for the Cu-mediated highly regioselective N-arylation of 1Hindole derivatives and 9H-carbazole.