RESUMO
1,1-Bis(iodozincio)alkanes are used as dinucleophilic linchpins in an enantioselective double cross-coupling reaction sequence involving aryl iodides and then thioesters. The two catalytic C-C bond-forming reactions are achieved in the same pot through two distinct palladium-based catalytic systems: a first non-enantioselective one delivering configurationally labile secondary benzylzinc species from an achiral precursor, and a second enantioconvergent one that operates a highly efficient dynamic kinetic resolution of the racemic intermediates. This strategy, new in the area of asymmetric synthesis through two consecutive electrophilic substitution reactions of geminated C(sp3 )-organodimetallics, provides useful methodology to access in a modular fashion acyclic α-disubstituted ketone products with very high enantiomeric purity.
RESUMO
The palladium-catalyzed direct arylation of azoles with (hetero)aryl halides is nowadays one of the most versatile and efficient procedures for the selective synthesis of heterobiaryls. Although this procedure is, due to its characteristics, also of great interest in the industrial field, the wide use of a reaction medium such as DMF or DMA, two polar aprotic solvents coded as dangerous according to environmental, health, safety (EHS) parameters, strongly limits its actual use. In contrast, the use of aromatic solvents as the reaction medium for direct arylations, although some of them show good EHS values, is poorly reported, probably due to their low solvent power against reagents and their potential involvement in undesired side reactions. In this paper we report an unprecedented selective C-5 arylation procedure involving anisole as an EHS green reaction solvent. In addition, the beneficial role of benzoic acid as an additive was also highlighted, a role that had never been previously described.
