Restricted Rotation in Aryl Olefins. I. Preparation and Resolution of β-Chloro-β-(2,4,6-trimethyl-3-bromophenyl)-α-methylacrylic Acid

Atroposelective Synthesis of Axially Chiral Styrenes via an Asymmetric C–H Functionalization Strategy

“…[3][4][5][6][7][8] In distinct contrast to the well-investigated axially chiral biaryls, [9][10][11][12][13][14] axially chiral styrenes, which exhibit a chiral axis between a substituted alkene and an aromatic ring have been largely overlooked, 15 despite the fact that this type of axial chirality was realized and intensively studied by Adams and co-workers in the 1940s. 16 The main hurdle is basically due to the flexible structure, which results in relatively lower barriers to rotation in comparison with their biaryl counterparts, rendering their asymmetric synthesis drastically more difficult (Scheme 1A). 15,16 On the other hand, axially chiral styrenes have flourished gradually, as chiral olefins can not only be employed as synthons for total synthesis 17 but also can be applied to asymmetric synthesis as chiral catalysts or ligands.…”

Synthesis of Axially Chiral Styrenes through Pd‐Catalyzed Asymmetric C−H Olefination Enabled by an Amino Amide Transient Directing Group

“…Mechanistic studies suggest that C À H cleavage is the enantioselectivity-determining step.Axially chiral styrenes, a class of atropoisomers arising from the sterically hindered rotation along a single bond between a substituted alkene and an aromatic ring, were first studied by Adams and co-workers in the 1940s. [1] This novel type of atropoisomers has been overlooked for a long time and received attentions only recently. These atropoisomers have been used as versatile synthons in total synthesis [2] and as chiral ligands in asymmetric catalysis.…”

Carbene-Catalyzed Atroposelective Synthesis of Axially Chiral Styrenes Bearing Acyclic Alkenes

“…In contrast, axially chiral styrenes, which bear a chiral axis between a simple alkene and an aryl ring, are much less developed although this kind of chirality was realized and intensively studied by Adams and co-workers in the 1940s. 14,23,24 Atroposelective access to axially chiral styrenes, especially those bearing acyclic alkene units, is challenging due to low rotational barrier, weak con gurational stability, and di cult control of the alkene E/Z selectivity (Fig. 1a).…”

“…1a). 23,24 In the past, synthetic success were mainly limited to aryl-cycloalkene connections in which the alkene is trapped in a ring to imitate the rigidity of biaryls and increase conformational stability [25][26][27][28][29][30][31][32] . It is only till recent years that several approaches emerged for asymmetric access to axially chiral aryl-acyclic alkene scaffolds.…”