Axially chiral alkenes: Atroposelective synthesis and applications

Torsional Strain‐Independent Catalytic Enantioselective Synthesis of Biaryl Atropisomers

“…In addition, the ester group in 7 a could be facilely reduced to give the corresponding primary alcohol 10 by the use of LiAlH 4 . Moreover, the oxidation of 7 a in the presence of PhI(OAc) 2 and MeOH worked well to deliver a styrene‐type atropisomer [22] 11 without any loss of ee. Furthermore, 7 a could be converted to a gem ‐diphenyl tertiary alcohol 12 through a two‐step procedure, and the ee value remained unchanged.…”

Enone as TFO Linker: Synthesis and Parallel DNA Triplex Stability Evaluation

“…3 : 2 according to 1 H NMR of the olefinic C−H in enone bond). The axial chirality is known in aromatic amides due to aryl‐C=O atropoisomerism, [25] while alkene‐indole skeleton has low rotational barriers leading to very low configurational stability [26] . According to conformational energy calculations, the potential energy barrier of rotation around C3 (indole)‐enone single bond were 9.90 and 48.89 kcal/mol for compound 4 and 9 , respectively (Figure S1).…”

Organocatalyzed asymmetric dearomative 1,3‐dipolar cycloaddition of 2‐nitrobenzofurans and N‐2,2,2‐trifluoroethylisatin ketimines

“…During the preparation of this manuscript, Albrecht and coworkers also reported the similar reaction with a cinchona‐derived squaramide as the catalyst (18 cases, >20:1 dr and 77–92% ee) 62 . However, after our extensive and in‐depth research, we successfully discovered that a more readily available chiral cyclohexanediamine‐derived bifunctional tertiary amine‐squaramide catalyst 64–66 could readily catalyze the asymmetric dearomative 1,3‐dipolar cycloaddition reaction of 2‐nitrobenzofurans and N ‐2,2,2‐trifluoroethylisatin ketimines in very high efficiency as well as with excellent diastereoselectivity and enantioselectivity (25 examples, up to 99% yield, >20:1 dr in all cases, and 95–99% ee) under mild reaction conditions (Scheme 1). Moreover, this protocol also shows striking features including wide functional group tolerance, great potential for scale‐up synthesis, and attractive product diversification.…”

“…61 During the F I G U R E 1 Selected compounds containing hydrobenzofuran and spirocyclic pyrrolidineoxindole moieties, respectively, and the modular merging strategy for the spiro-fused polyheterocyclic molecular skeletons S C H E M E 1 Readily available chiral cyclohexanediamine-derived bifunctional tertiary aminesquaramide enabling the highly diastereoselective and enantioselective dearomative 1,3-dipolar cycloaddition of 2-nitrobenzofurans and N-2,2,2-trifluoroethylisatin ketimines preparation of this manuscript, Albrecht and coworkers also reported the similar reaction with a cinchonaderived squaramide as the catalyst (18 cases, >20:1 dr and 77-92% ee). 62 However, after our extensive and indepth research, we successfully discovered that a more readily available chiral cyclohexanediamine-derived bifunctional tertiary amine-squaramide catalyst [64][65][66] could readily catalyze the asymmetric dearomative 1,3-dipolar cycloaddition reaction of 2-nitrobenzofurans and N-2,2,2-trifluoroethylisatin ketimines in very high efficiency as well as with excellent diastereoselectivity and enantioselectivity (25 examples, up to 99% yield, >20:1 dr in all cases, and 95-99% ee) under mild reaction conditions (Scheme 1). Moreover, this protocol also shows striking features including wide functional group tolerance, great potential for scale-up synthesis, and attractive product diversification.…”