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Minisci reactions: Versatile CH-functionalizations for medicinal chemists

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Minisci reactions: Versatile CH-functionalizations for medicinal chemists

Matthew A. J. Duncton *
Renovis, Inc. (a wholly-owned subsidiary of Evotec AG), Two Corporate Drive, South San Francisco, CA 94080, United States. E-mail: mattduncton@yahoo.com; Tel: +1 917-345-3183

Received 24th May 2011 , Accepted 3rd July 2011

First published on the web 22nd August 2011

http://pubs.rsc.org/en/content/articlehtml/2011/md/c1md00134e

http://pubs.rsc.org/en/content/articlehtml/2011/md/c1md00134e

http://pubs.rsc.org/en/content/articlehtml/2011/md/c1md00134e

http://pubs.rsc.org/en/content/articlehtml/2011/md/c1md00134e

http://pubs.rsc.org/en/content/articlehtml/2011/md/c1md00134e

http://pubs.rsc.org/en/content/articlehtml/2011/md/c1md00134e


The addition of a radical to a heteroaromatic base is commonly referred to as a Minsici reaction. Such reactions constitute a broad-set of selective CH-functionalization processes. This review describes some of the major applications of Minisci reactions and related processes to medicinal or biological chemistry, and highlights some potential developments within this area.


Introduction

The aim of this review is to summarize the use of Minisci reactions within medicinal chemistry, and to highlight some future opportunities to continue progression of this chemistry. As such, it is not an aim that detailed mechanistic information, or a comprehensive list of examples be described. For this, the reader is directed to excellent articles from Minisci, Harrowven and Bowman.1–3 Rather, the review is written to show that Minisci reactions are extremely valuable CH-functionalization processes within medicinal chemistry. However, their use has been somewhat under-utilized when compared with other well-known selective transformations (e.g. palladium-catalysed cross-couplings). Therefore, it is hoped that in the future, Minisci chemistry will continue to develop, such that the reactions become a staple-set of methods for medicinal and biological chemists alike.

To aid discussion, the review is divided in to several sections. First, some historical perspective is given. This is followed by a discussion of scope and limitations. The main-body of the review describes some specific examples of Minisci reactions and related processes, with a focus on their use within medicinal, or biological chemistry. Finally, brief mention is given to potential future applications, some of which may be beneficial in providing ‘high-content’ diverse libraries for screening.

 

http://pubs.rsc.org/en/content/articlehtml/2011/md/c1md00134e

http://pubs.rsc.org/en/content/articlehtml/2011/md/c1md00134e

http://pubs.rsc.org/en/content/articlehtml/2011/md/c1md00134e

http://pubs.rsc.org/en/content/articlehtml/2011/md/c1md00134e

http://pubs.rsc.org/en/content/articlehtml/2011/md/c1md00134e

http://pubs.rsc.org/en/content/articlehtml/2011/md/c1md00134e

http://pubs.rsc.org/en/content/articlehtml/2011/md/c1md00134e

http://pubs.rsc.org/en/content/articlehtml/2011/md/c1md00134e

http://pubs.rsc.org/en/content/articlehtml/2011/md/c1md00134e

http://pubs.rsc.org/en/content/articlehtml/2011/md/c1md00134e

http://pubs.rsc.org/en/content/articlehtml/2011/md/c1md00134e

http://pubs.rsc.org/en/content/articlehtml/2011/md/c1md00134e

 

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WIKI

The Minisci reaction is a named reaction in organic chemistry. It is a radical substitution to an aromatic compound, in particular to a heteroaromatic base, that introduces an alkyl group. The reaction was published about in 1971 by F. Minisci.[1] The aromatic compound is generally electron-deficient and with N-aromatic compounds the nitrogen atom is protonated.[2] A typical reaction is that between pyridine and pivalic acid to 2-tert-butylpyridine with silver nitrate, sulfuric acid and ammonium persulfate. The reaction resembles Friedel-Crafts alkylation but with opposite reactivity and selectivity.[3]

The Minisci reaction proceeds regioselectively and enables the introduction of a wide range of alkyl groups.[4] A side-reaction is acylation.[5] The ratio between alkylation and acylation depends on the substrate and the reaction conditions. Due to the simple raw materials and the simple reaction conditions the reaction has many applications in heterocyclic chemistry.[6][7]

Reaction between pyridine and pivalic acid to 2-tert-butylpyridine

Mechanism

A free radical is formed from the carboxylic acid in an oxidative decarboxylation with silver salts and an oxidizing agent. The oxidizing agent reoxidizes the silver salt. The radical then reacts with the aromatic compound. The ultimate product is formed by rearomatisation. The acylated product is formed from the acyl radical.[4][5]

Mechanism of the Minisci-Reaction

References

  1. F. Minisci, R. Bernardi, F. Bertini, R. Galli, M. Perchinummo: Nucleophilic character of alkyl radicals—VI : A new convenient selective alkylation of heteroaromatic bases, in: Tetrahedron 1971, 27, 3575–3579.
  2. Minisci reaction Jie Jack Li in Name Reactions 2009, 361-362, doi:10.1007/978-3-642-01053-8_163
  3. Strategic applications of named reactions in organic synthesis: background and detailed mechanisms László Kürti, Barbara Czakó 2005
  4. F. Fontana, F. Minisci, M. C. N. Barbosa, E. Vismara: Homolytic acylation of protonated pyridines and pyrazines with α-keto acids: the problem of monoacylation, in: J. Org. Chem. 1991, 56, 2866–2869; doi:10.1021/jo00008a050.
  5. M.-L. Bennasar, T. Roca, R. Griera, J. Bosch: Generation and Intermolecular Reactions of 2-Indolylacyl Radicals, in: Org. Lett. 2001, 3, 1697–1700; doi:10.1021/ol0100576.
  6. P. B. Palde, B. R. McNaughton, N. T. Ross, P. C. Gareiss, C. R. Mace, R. C. Spitale, B. L. Miller: Single-Step Synthesis of Functional Organic Receptors via a Tridirectional Minisci Reaction, in: Synthesis 2007, 15, 2287–2290; doi:10.1055/s-2007-983792.
  7. J. A. Joules, K. Mills: Heterocyclic Chemistry, 5. Auflage, S. 125–141, Blackwell Publishing, Chichester, 2010, ISBN 978-1-4051-9365-8.

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DR ANTHONY CRASTO

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DR ANTHONY MELVIN CRASTO Ph.D

DR ANTHONY MELVIN CRASTO Ph.D

DR ANTHONY MELVIN CRASTO, Born in Mumbai in 1964 and graduated from Mumbai University, Completed his Ph.D from ICT, 1991,Matunga, Mumbai, India, in Organic Chemistry, The thesis topic was Synthesis of Novel Pyrethroid Analogues, Currently he is working with GLENMARK PHARMACEUTICALS LTD, Research Centre as Principal Scientist, Process Research (bulk actives) at Mahape, Navi Mumbai, India. Total Industry exp 30 plus yrs, Prior to joining Glenmark, he has worked with major multinationals like Hoechst Marion Roussel, now Sanofi, Searle India Ltd, now RPG lifesciences, etc. He has worked with notable scientists like Dr K Nagarajan, Dr Ralph Stapel, Prof S Seshadri, Dr T.V. Radhakrishnan and Dr B. K. Kulkarni, etc, He did custom synthesis for major multinationals in his career like BASF, Novartis, Sanofi, etc., He has worked in Discovery, Natural products, Bulk drugs, Generics, Intermediates, Fine chemicals, Neutraceuticals, GMP, Scaleups, etc, he is now helping millions, has 9 million plus hits on Google on all Organic chemistry websites. His friends call him Open superstar worlddrugtracker. His New Drug Approvals, Green Chemistry International, All about drugs, Eurekamoments, Organic spectroscopy international, etc in organic chemistry are some most read blogs He has hands on experience in initiation and developing novel routes for drug molecules and implementation them on commercial scale over a 30 year tenure till date Dec 2017, Around 35 plus products in his career. He has good knowledge of IPM, GMP, Regulatory aspects, he has several International patents published worldwide . He has good proficiency in Technology transfer, Spectroscopy, Stereochemistry, Synthesis, Polymorphism etc., He suffered a paralytic stroke/ Acute Transverse mylitis in Dec 2007 and is 90 %Paralysed, He is bound to a wheelchair, this seems to have injected feul in him to help chemists all around the world, he is more active than before and is pushing boundaries, He has 9 million plus hits on Google, 2.5 lakh plus connections on all networking sites, 50 Lakh plus views on dozen plus blogs, He makes himself available to all, contact him on +91 9323115463, email amcrasto@gmail.com, Twitter, @amcrasto , He lives and will die for his family, 90% paralysis cannot kill his soul., Notably he has 19 lakh plus views on New Drug Approvals Blog in 216 countries......https://newdrugapprovals.wordpress.com/ , He appreciates the help he gets from one and all, Friends, Family, Glenmark, Readers, Wellwishers, Doctors, Drug authorities, His Contacts, Physiotherapist, etc

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