Various commonly used organic solvents were dried with several different drying agents. A glovebox-bound coulometric Karl Fischer apparatus with a two-compartment measuring cell was used to determine the efficiency of the drying process. Recommendations are made relating to optimum drying agents/conditions that can be used to rapidly and reliably generate solvents with low residual water content by means of commonly available materials found in most synthesis laboratories. The practical method provides for safer handling and drying of solvents than methods calling for the use of reactive metals, metal hydrides, or solvent distillation.

/pdf/drying-of-organic-solvents-quantitative-evaluation-of-the-4v6wtakg15.pdf

Drying of Organic Solvents: Quantitative Evaluation of the Efficiency of Several Desiccants

Mild, efficient, copper-catalyzed N-arylation procedures for nitrogen heterocycles, amides, carbamates, and C-arylation procedures for malonic acid derivatives have been developed that afford high yields of arylated products with excellent selectivity. The N-arylation of imidazole with aryl bromides or iodides was found to be greatly accelerated by inexpensive, air-stable catalyst systems, combining catalytic copper salts or oxides with a set of structurally simple chelating ligands. The reaction was shown to be compatible with a broad range of aryl halides, encompassing sterically hindered, electron-poor, and electron-rich ones, providing the arylated products under particularly mild conditions (50-82 degrees C). The lower limit in ligand and catalyst loading and the scope of Ullmann-type condensations catalyzed by complexes bearing those ligands with respect to the nucleophile class have also been investigated. Chelating Schiff base Chxn-Py-Al (1c) generates a remarkably general copper catalyst for N-arylation of pyrrole, indole, 1,2,4-triazole, amides, and carbamates; and C-arylation of diethyl malonate, ethyl cyanoacetate, and malononitrile with aryl iodides under mild conditions (50-82 degrees C). The new method reported here is the most successful to date with regard to Ullmann-type arylation of some of these nucleophiles.

https://onlinelibrary.wiley.com/doi/pdf/10.1002/chem.200400582

Highly efficient and mild copper-catalyzed N- and C-arylations with aryl bromides and iodides.

Recent advances in the preparation and synthetic applications of oxiranes

In developing a process the chemist may encounter water in the roles of impurity, beneficial additive, or solvent. This chapter discusses some examples of water as solvent and cosolvent. Water may also be necessary in the crystallization of a desired hydrate. Quantitation can be straightforward if standard data points have been generated that use known amounts of water in the presence of the primary compound to be assayed. The presence of water may be inferred by thermogravimetric assay; however, any weight loss may not be specific for water. This chapter also examines some of the more subtle effects of water on processing. Some reagents react with water very quickly and exothermically. Water can enter a reaction as part of the air, solvents, reagents, or by-products of a reaction, or it can enter as a contaminant in equipment. Many reactions are essentially dehydrations, and the water generated can inhibit the desired reaction. Solvents may be selected to remove water azeotropically during the reaction.

Effects of Water

Regioselective C–H functionalization of arenes has widespread applications in synthetic chemistry. The regioselectivity of these reactions is often controlled by directing groups or steric hindrance ortho to a potential reaction site. Here, we report a catalytic intermolecular C–H silylation of unactivated arenes that manifests very high regioselectivity through steric effects of substituents meta to a potential site of reactivity. The silyl moiety can be further functionalized under mild conditions but is also inert toward many common organic transformations, rendering the silylarene products useful building blocks. The remote steric effect that we observe results from the steric properties of both the rhodium catalyst and the silane.

http://science.sciencemag.org/content/sci/343/6173/853.full.pdf

Rhodium-catalyzed intermolecular C-H silylation of arenes with high steric regiocontrol.

https://www.chem.tamu.edu/rgroup/gladysz/documents/nmr6.pdf

Desiccant efficiency in solvent drying. 3. Dipolar aprotic solvents

Stereospecific generation of 2-oxyallylic cations from two new sources. Steric course of cycloaddition to conjugated dienes

Allylsilanes and vinylsilanes usually react with electrophiles to give substitution. These reactions are conveniently understood as the reactions of alkenes that have been significantly but only slightly modified by the presence of the silyl group. In both reactions, substitution is favored over addition, and both the site of attack and the site of the double bond in the product are usually determined by the site of the silyl group in the starting material.



In this chapter only the electrophilic substitution reactions of allylsilanes, vinylsilanes, and allenylsilanes is discussed. It is further restricted to the reactions of tetraorganosilanes because they are synthetically the most interesting in the laboratory. However, although they are not included in the tables, allylsilanes and vinylsilanes that react by addition rather than substitution or that are not tetraorganosilanes are referred to occasionally in the text wherever their reactions illuminate the discussion. Many of the features of the reactions discussed here are shared by the reactions of arylsilanes, ethynylsilanes, propargylsilanes, cyclopropylsilanes, and cyclopropylmethylsilanes. The methods by which allylsilanes and vinylsilanes are synthesized have been summarized in several places.



Stereochemsitry of reactions of allenylsilanes and vinylsilanes is discussed. Scope and limitations include discussions of protodesilylation and deuterodesilyation and the use of carbon, nitrogen, and oxygen as electrophiles. Other electrophiles include phosphorus, sulfur, metals, halogens, and selenium. All of these are covered in the extensive tabular material


Keywords:

electrophilic substitution;
allyl silanes;
vinylsilanes;
mechanism;
stereochemistry;
reactivity;
regioselectivity;
scope;
limitation;
protodesilylation;
deuterodesilylation;
allenyl silanes;
carbon electrophiles;
catalysts;
nitrogen electrophiles;
oxygen electrophiles;
phosphorus electrophiles;
sulfur electrophiles;
aldehydes;
alkyl halides;
alcohols;
ethers;
nitro compounds;
epoxides;
carbonyls;
alkanes;
quinones;
acid chlorides;
acid anhydrides;
acetals;
experimental procedures

The Electrophilic Substitution of Allylsilanes and Vinylsilanes

https://www.chem.tamu.edu/rgroup/gladysz/documents/nmr8.pdf

Desiccant efficiency in solvent and reagent drying. 7. Alcohols

The Journal of Organic Chemistry is published by the American Chemical Society. 1155 Sixteenth Street N.W., Washington, DC 20036 Desiccant efficiency in solvent and reagent drying. 5. Amines David R. Burfield, Roger H. Smithers, and Andrew Sui Chai Tan J. Org. Chem., 1981, 46 (3), 629-631• DOI: 10.1021/jo00316a030 • Publication Date (Web): 01 May 2002 Downloaded from http://pubs.acs.org on May 1, 2009

https://www.chem.tamu.edu/rgroup/gladysz/documents/nmr7.pdf

Roger H. Smithers

Papers

Desiccant efficiency in solvent drying. 3. Dipolar aprotic solvents

Stereospecific generation of 2-oxyallylic cations from two new sources. Steric course of cycloaddition to conjugated dienes

The Electrophilic Substitution of Allylsilanes and Vinylsilanes

Desiccant efficiency in solvent and reagent drying. 7. Alcohols

Desiccant efficiency in solvent and reagent drying. 5. Amines