Nicholas E. Leadbeater

Palladium-catalyzed decarboxylative coupling of aromatic acids with aryl halides or unactivated arenes using microwave heating

Microwave heating greatly accelerates Pd-catalyzed decarboxylative coupling of aromatic acids and aryl iodides, and allows the coupling of benzoic acids with unactivated arenes.

Microwave energy: a versatile tool for the biosciences

As the range of techniques for microwave heating has expanded, so have the areas in which it can have a profound impact. Two emerging areas are the application of microwave heating for the synthesis of peptides, peptoids, oligopeptides and carbohydrates and in the field of proteomics.

Fast, easy, clean chemistry by using water as a solvent and microwave heating: the Suzuki coupling as an illustration

Water is an excellent solvent for organic chemistry and microwave heating offers a very efficient way of heating reaction mixtures. In this article, by focusing on the Suzuki reaction, it is shown how these two methods, used alone or together, can impact modern synthetic chemistry, making reactions faster, easier and cleaner.

Cross coupling: When is free really free?

An organocatalytic method for constructing biaryls joins an increasing number of articles reporting metal-free analogues to reactions that traditionally have required a transition-metal catalyst. What does it take to prove that metal is not involved, and does it really matter?

Ligand-free palladium catalysis of aryl coupling reactions facilitated by grinding

Abstract Ligand-free palladium-catalysed Suzuki coupling reactions and homo-couplings of boronic acids have been facilitated by grinding. The reactions are rapid (10–30 min) and can be performed without the need to exclude air and moisture.

Trifluoromethyl ketones: properties, preparation, and application

Trifluoromethyl ketones (TFMKs) are exceedingly valuable synthetic targets in their own right and as synthons in the construction of fluorinated pharmacons. This Feature Article provides an overview of the properties of TFMKs, an in-depth discussion of the methods available for their synthesis, and two illustrative examples of their application as key intermediates in medicinal chemistry.

Microwave-promoted organic synthesis using ionic liquids: a mini review.

Due to their extraordinary properties, such as the ionic composition, good thermal stability, low vapor pressure, and solution interactions, ionic liquids can be used as solvents, reagents, and heating aids in conjunction with microwave chemistry. Synthesis of diverse molecules can be improved with the use of the ionic liquids assisted microwave heating due to fast reaction times, simple reaction work-up, and catalyst recovery. This mini-review outlines this newly emerging field.

Ionic liquids as reagents and solvents in conjunction with microwave heating: rapid synthesis of alkyl halides from alcohols and nitriles from aryl halides

We show that using ionic liquids as reagents in conjunction with microwave heating it is possible to prepare primary alkyl halides from the corresponding alcohols rapidly. Using ionic liquids as solvents in conjunction with microwave heating it is possible to prepare aryl nitriles from the corresponding aryl bromides or iodides. The scope and limitations of using microwave-promotion as a tool in these reactions is discussed.

Synthesis of 4-acetamido-2,2,6,6-tetramethylpiperidine-1-oxoammonium tetrafluoroborate and 4-acetamido-(2,2,6,6-tetramethyl-piperidin-1-yl)oxyl and their use in oxidative reactions

We describe the synthesis of the lesser-known stoichiometric oxidation reagent 4-acetamido-2,2,6,6-tetramethylpiperidine-1-oxoammonium tetrafluoroborate (1, Bobbitts salt), as well as of 4-acetamido-(2,2,6,6-tetramethyl-piperidin-1-yl)oxyl (2, AcNH-TEMPO). Several representative oxidation reactions are also presented to demonstrate the salts oxidative capabilities. Bobbitts salt has a range of applications, from the oxidation of various alcohols to their corresponding carbonyl derivatives to the oxidative cleavage of benzyl ethers, whereas 2 has been shown to serve as a catalytic or stoichiometric oxidant. The oxyl radical can be obtained in 85% yield over two steps on a 1-mole scale from commercially available 4-amino-2,2,6,6-tetramethylpiperidine (5), and is far more cost-effective to prepare in-house than purchase commercially. An additional step converts the oxyl radical into the oxoammonium salt (1, Bobbitts salt) in 88% yield, with an overall yield of 75%. The synthesis of the salt takes ∼5 d to complete. Oxoammonium salts are metal-free, nontoxic and environmentally friendly oxidants. Preparation of 1 is also inherently ′green′, as water can be used as the solvent and the use of environmentally unfriendly materials is minimal. Moreover, after it has been used, the spent oxidant can be recovered and used to regenerate 1, thereby making the process recyclable.

Use of Raman spectroscopy as a tool for in situ monitoring of microwave-promoted reactions.

The progress of microwave-promoted reactions can be monitored by interfacing a Raman spectrometer with a scientific microwave unit. The apparatus is assembled from commercially available components. It is used in this protocol to follow the base-catalyzed reaction of salicylaldehyde with ethylacetoacetate to yield 3-acetylcoumarin. It is possible to watch the reaction spectroscopically in real time, determine when it reaches completion and thus use it as a tool for rapid reaction optimization.