A strategy for establishing a chiral axis from stereogenic centers via elimination or oxidative aromatization with a high level of chirality transfer was developed.

Axially chiral biaryls are core structures of increasingly important organic molecules including bioactive natural products, drugs, chiral ligands and organocatalysts. Among established methods for accessing these axially chiral structures, chiral ortho‐auxiliaries/substituents and remote stereogenic centers have provided useful strategies for the preparation of highly functionalized enantiopure biaryl compounds such as gossypol, rugulotrosin A, korupensamine A, phosphine ligands, sulfoxides, and 2‐amino‐2′‐hydroxy‐1,1′‐binaphthyls (NOBINs). These strategies, which entail point‐to‐axial chirality transfer, have received increasing attention in the last thirty years. This minireview up to October 2019 describes these methods with attention to the atropselective formation of biaryl systems influenced by chiral ortho‐auxiliaries/substituents and remote stereogenic centers.

The α-alkylation of ketones and their derivatives by the addition of their corresponding enolates to alkyl halides is a fundamental synthetic transformation, but its utility is limited because the key bond-forming step proceeds in a bimolecular nucleophilic substitution fashion. Here we describe how an umpolung strategy that involves the addition of Grignard reagents to α-epoxy N-sulfonyl hydrazones-directed by the alkoxide of the 1-azo-3-alkoxy propenes formed in situ via base-induced ring opening of the epoxide-leads to the syn-selective production of α-alkyl-β-hydroxy N-sulfonyl hydrazones with α-quaternary centres. This transformation is remarkable in its ability to incorporate an unprecedented range of carbon-based substituents, which include primary, secondary and tertiary alkyl, as well as alkenyl, aryl, allenyl and alkynyl groups. Subsequent hydrolysis of the β-hydroxy N-sulfonyl hydrazone products produces the corresponding β-hydroxy ketones. In addition to hydrolysis, the hydrazone products are poised to undergo numerous different known synthetic transformations via well-established chemistry, which would provide access to a wide array of useful structures.

No abstract

Twelve common density functional methods and seven basis sets for geometry optimization were evaluated on the accuracy of 1 H/ 13 C NMR chemical shift calculations for biaryls. For these functionals, 1 H shifts calculations for gas phase optimized geometries were significantly less accurate than those for in-solution optimized structures, while 13 C results were not strongly influenced by geometry optimization methods and solvent effects. B3LYP, B3PW91, mPW1PW91 and ω B97XD were the best-performing functionals with lowest errors; among seven basis sets, DGDZVP2 and 6-31G(d,p) outperformed the others. The combination of these functionals and basis sets resulted in high accuracy with CMAE min = 0.0327 ppm (0.76%) and 0.888 ppm (0.58%) for 1 H and 13 C, respectively. The selected functionals and basis set were validated when consistently producing optimized structures with high accuracy results for 1 H and 13 C chemical shift calculations of two other biaryls. This study highly recommends the IEFPCM/B3LYP, B3PW91, mPW1PW91 or ω B97XD/DGDZVP2 or 6-31G(d,p) level of theory for the geometry optimization step, especially the solvent incorporation, which would lead to high accuracy 1 H/ 13 C calculation. This work would assist in the fully structural assignments of biaryls and provide insights into in-solution biaryl conformations.