Modern organic synthesis

The Suzuki reaction (the palladium-catalyzed cross-coupling of aryl halides with boronic acids) is arguably one of the most versatile and at the same time also one of the most often used cross-coupling reactions in modern organic synthesis [32], Carrying out high-speed Suzuki reactions under controlled microwave conditions can today be considered almost a routine synthetic procedure, given the enormous literature precedent for this transformation [7]. 

One of the main trends in modern organic synthesis is the use of efficient and selective reaction sequences, which make it possible to assemble target molecules from simple precursors with the use of a minimum number of operations (technological steps). 

Jahnisch K, Baems M, Hessel V, Ehrfeld W, Haverkamp V, Lowe H, Wille C, Guber A (2000) Direct fluorination of toluene using elemental fluorine in gas/hquid microreactors. J Fluorine Chem 105 117-128 Jahnisch K, Hessel V, Lowe H, Baems M (2004) Chemistry in microstructured reactors. Angew Chem Int Ed 43 406-446 Kappe CO (2004) Controlled microwave heating in modern organic synthesis. Angew Chem Int Ed 43 6250-6284... 

Kappe O (2004) Controlled microwave heating in modern organic synthesis. Angew Chem Int Ed 43 6250-6284... 

Ley SV, Baxendale IR (2002b) New tools and concepts for modern organic synthesis. Nat Rev Drug Disc 1 573-586 Ley S V, Massi A (2000) J Comb Chem Polymer supported reagents in synthesis preparation of bicyclo[2.2.2]octane derivatives via tandem michael addition reactions and subsequent combinatorial decoration. 2 104—107 Ley SV, Schucht O, Thomas AW, Murray PJ (1999) Synthesis of the alkaloids ( )-oxomaritidine and ( )-epimaritidine using an orchestrated multi-step sequence of polymer supported reagents. J Chem Soc Perkin Trans 1 1251— 1252... 

Although more than a century has passed since the first preparation of titanium and zirconium species, modern organic synthesis continues to benefit from the unique versatility of these organometallic derivatives. 

Thioxotetrahydro-l,3-0,iV-lieterocycles are commonly named cyclic thiocarbamates or thionocarbamates. The structural association of five- and six-membered thionocarbamates with diverse carbohydrate scaffolds has shown a promising potential in modern organic synthesis and in the preparation of biomolecules mimics. The principal pathways for their synthesis, the recent and most important developments of their chemical transformations as well as some examples of their biological activities will be considered in the following discussion. 

The rhodium( 11)-catalyzed formation of 1,3-dipoles has played a major role in facilitating the use of the dipolar cycloaddition reaction in modern organic synthesis. This is apparent from the increasing number of applications of this chemistry for the construction of heterocyclic and natural product ring systems. This chapter initially focuses on those aspects of rhodium(II) catalysis that control dipole formation and reactivity, and concludes with a sampling of the myriad examples that exist in the Hterature today. 

Chapter 1 focuses on how to design and execute the synthesis of a variety of target molecules (TM) using the tools and strategies you encountered in Modern Organic Synthesis An Introduction. 

R ac.tL jity umpoiung and 6ynthztic e.quivaJte.ntA are very fruitful concepts in modern organic synthesis, in particular for the multistep preparation of natural compounds. In this area, organo-phosphorus compounds can be useful tools, particularly for reversible umpolung by heteroatom exchange (.1.-4). 

Olefin metathesis has come rightly to occupy a key role in modern organic synthesis, especially in natural product and polymer synthesis, eventually leading... 

Until recently organic photochemistry has only partially focused on stereoselective synthesis, one of the major challenges and research areas in modern organic synthesis. This situation has dramatically changed in the last decade and highly chemo-, regio-, diastereo- as well as enantioselective reactions have been developed. Chemists all over the world became aware of the fascinating synthetic opportunities of electronically excited molecules and definitely this will lead to a new period of prosperity. Photochemical reactions can be performed at low temperatures, in the solid or liquid state or under gas-phase conditions, with spin-selective direct excitation or sensitization, and even multi-photon processes start to enter the synthetic scenery. 

The oxidative activation of arenes is a powerful and versatile synthetic tactic that enables dearomatization to give useful synthons. Central to this chemistry are hydroxylated arenes or arenols, the phenolic functions of which can be exploited to facilitate the dearomatizing process by two-electron oxidation. Suitably substituted arenols can hence be converted, with the help of oxygen- or carbon-based nucleophiles, into ortho-quinone monoketals and ortho-quinols. These 6-oxocyclohexa-2,4-dienones are ideally functionalized for the construction of many complex and polyoxygenated natural product architectures. Today, the inherent and multiple reactivity of arenol-derived ortho-quinone monoketals and ortho-quinols species is finding numerous and, in many cases, biomimetic applications in modern organic synthesis. 

Reagents and complexes containing transition metals are important in modern organic synthesis because they allow apparently impossible reactions to occur easily. This chemistry com-... 

We have selected a few reactions of Co, Fe, and Cu with honourable mentions for Pt, Ir, and Cr. We could have focused on other elements—Ni, W, Ti, Zr, Mn, Ru, and Rh all have special reactions, Transition metal chemistry, particularly involving palladium catalysis, occupies a central role in modern organic synthesis because complex structures can be assembled in few steps with impressive regio- and stereochemical control. There are many books devoted entirely to this subject if you wish to take it further. 

Few organic transformations add as much molecular complexity in one step as the Pauson-Khand reaction. This reaction is one of the best examples of how organometallic chemistry is useful in modern organic synthesis, and can serve as a key tool for the synthesis of natural products, in this case those possessing cyclopentane units. The limited scope, low yields and lack of efficient catalytic procedures were serious drawbacks in the past that have been... 

The Diels-Alder reaction and catalytic processes are powerful methods of modern organic synthesis. In both these areas organoboranes play an important role being used as dienophiles,1 and hydroborating agents.2... 

In much the same way, the transformation of the vast potential of organic chemistry of the 1930s and 1940s into the near omnipotence of modern organic synthesis was achieved not owing to the discovery of new fundamental principles... 

Not much could be added to the above quotations with regard to the role of both imagination and knowledge as complementary components of the true creativity in organic synthesis (or, for that matter, in any other area of both science and art). In the context of this chapter, however, it is essential to take a closer look at the rational background of modern organic synthesis, and its logistics as especially important components of the problem solutions in this area. 

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