Axially chiral alkenes: Atroposelective synthesis and applications

Axial chirality is historically epitomized by biaryl compounds containing rotationally impeded aryl-aryl linkage. As the field of atroposelective catalysis advances, the synthesis and application of less common scaffolds such as alkenes have now come to the fore. The manifestation of axial chirality in aryl alkenes was hypothesized in 1928 and the first resolution was achieved nearly a decade later. However, catalytic asymmetric construction of axially chiral open-chain alkenes appeared only in 2017 which ushered in a renewed focus on these structures. In principle, axially chiral alkenes possess an alkene group tethered at one end of the stereogenic axis, which greatly reduces the overall rigidity. To date, atropisomers with C (vinyl)-C (aryl) and C (vinyl)-heteroatom bond have been reported. Considering the rapid growth in the synthesis and synthetic utility of axially chiral open-chain alkenes, this review intends to provide a historical overview and discusses these new developments. It is hope that this timely discussion would motivate continued growth of this nascent field.