The 1 H and 13 C NMR chemical shifts of 48 industrially preferred solvents in six commonly used deuterated NMR solvents (CDCl 3 , acetone-d 6 , DMSO-d 6 , acetonitrile-d 3 , methanol-d 4 , and D 2 O) are reported. This work supplements the compilation of NMR data published by Gottlieb, Kotlyar, and Nudelman (J. Org. Chem. 1997, 62, 7512) by providing spectral parameters for solvents that were not commonly utilized at the time of their original report. Data are specifically included for solvents, such as 2-Me-THF, n-heptane, and iso-propyl acetate, which are being used more frequently as the chemical industry aims to adopt greener, safer, and more sustainable solvents. These spectral tables simplify the identification of these solvents as impurities in NMR spectra following their use in synthesis and workup protocols.

Reaction discovery using N-heterocyclic carbene organocatalysis has been dominated by the chemistry of acyl anion equivalents. Recent studies demonstrate that NHCs are far more diverse catalysts, with a variety of reactions discovered that proceed without acyl anion equivalent formation. In this tutorial review selected examples of acyl anion free NHC catalysis using carbonyl compounds are presented.

Catalytic generation of alpha,beta-unsaturated acyl imidazolium cations and enolates has been achieved, and their involvement in a Michael addition acylation sequence exploited, to provide a range of dihydropyranones. alpha,beta-Unsaturated enol esters, or alpha,beta-unsaturated acid fluorides in association with TMS enol ethers, serve as appropriate substrates for this reaction. The transformation can also be achieved enantioselectively using catalysts derived from chiral triazolium salts.

The reaction of acid fluorides with N-heterocyclic carbenes (NHCs) produces anhydrous acyl azolium fluorides. With appropriate selection of acid fluoride and NHC, these salts can be used for the room temperature SNAr fluorination of a variety of aryl chlorides and nitroarenes.

This paper describes the room-temperature S(N)Ar fluorination of aryl halides and nitroarenes using anhydrous tetramethylammonium fluoride (NMe4F). This reagent effectively converts aryl-X (X = Cl, Br, I, NO2, OTf) to aryl-F under mild conditions (often room temperature). Substrates for this reaction include electron-deficient heteroaromatics (22 examples) and arenes (5 examples). The relative rates of the reactions vary with X as well as with the structure of the substrate. However, in general, substrates bearing X = NO2 or Br react fastest. In all cases examined, the yields of these reactions are comparable to or better than those obtained with CsF at elevated temperatures (i.e., more traditional halex fluorination conditions). The reactions also afford comparable yields on scales ranging from 100 mg to 10 g. A cost analysis is presented, which shows that fluorination with NMe4F is generally more cost-effective than fluorination with CsF.