Enantioselective C(sp2)–H borylation of diarylmethylsilanes catalyzed by chiral pyridine-dihydroisoquinoline iridium complexes

Chiral Bidentate Boryl Ligand-Enabled Iridium-Catalyzed Enantioselective Dual C–H Borylation of Ferrocenes: Reaction Development and Mechanistic Insights

“…Transition-metal-catalyzed asymmetric C–H borylation reactions have emerged as a viable approach for the asymmetric synthesis of optically active organoboron compounds . In this aspect, groups of Yu, Hartwig, Sawamura, Phipps, and Hong as well as our own group have developed new strategies and novel chiral ligands to enable a series of enantioselective C–H borylation reactions to build central chirality (Scheme B). However, establishing other types of chirality through an asymmetric C–H borylation protocol has lagged behind and still represents a formidable challenge.…”

Importance of favourable non-covalent contacts in the stereoselective synthesis of tetrasubstituted chromanones

“…Thus, even though the crystal structure of PyDHIQ bound to PdCl 2 exhibits an open conformation, one must consider both closed and open conformations of this ligand when developing stereochemical models of reactions in which it is utilized. For example, Hong et al 39 recently reported another use of PyDHIQ ligand 1c in an Ir catalysed C(sp 2 )-H borylation of diarylmethylsilanes. Due to the bulkiness of the Bpin group in the substrate and the possibility of both stabilizing and destabilizing interactions between the Bpin and benzyl groups of the ligand, it would be necessary to explore the 'closed' and 'open' conformers of the ligand to determine the factors responsible for this high degree of selectivity.…”

Development of Chiral Ligands for the Transition‐Metal‐Catalyzed Enantioselective Silylation and Borylation of C−H Bonds

“…Recently,H ong and coworkers also reported an iridium catalyst that contains ap yridyl dihydroisoquinoline ligand for the same reaction, but the enantioselectivity of the reactions catalyzed by this newly developed catalyst was highly dependent on the steric and electronic properties of the substrates;d iarylmethyl silanes containing electron-poor substituents on the arene led to the borylation products with low to moderate enantioselectivity. [35] After the discovery of iridium catalysts containing chiral N,N-ligands for the enantioselective borylation of C À H bonds,Sawamura and co-workers reported iridium complexes of chiral monophosphoramidite ligands for the enantioselec-tive borylation of 2-alkylpyridines.T he reaction occurred selectively at the b-C À Hb onds of the pyridyl group,b ut the enantioselectivity of the borylated products was low (Figure 20). [36] Thep yridyl group on the substrate played two roles.Itfunctioned as the directing group to control the siteselectivity of the borylation, and it acted as an auxiliary ligand that, together with the monophosphoramidite ligand, accelerated the borylation process.…”