Atropselective Synthesis of N,C-Bis(diphenylphosphanes) from Bridged 2-Arylindoles Based on Effective Point-to-Axial Asymmetric Inductions after an Unusual Dilithiation

Abstract

An asymmetric methanolysis of glutaric anhydride and 6 ensuing steps gave veratrol-annulated dimethylcycloheptenone diastereomers with 99% ee; ring closures occurred by Friedel−Crafts acylations of carboxylic acids obtained by stereospecific hydrogenolyses of a pair of diastereomeric δ-lactones. The mentioned cycloheptenones and Ph−NH−NH 2 underwent Fischer indole syntheses providing the tetracyclic indoles cis-and trans-14a, respectively. Double lithiations with BuLi and quenchings with ClPPh 2 furnished the diphosphanes cis-and trans-15 with perfect (P)-and (M)-atropselectivity, respectively.

Synthesis of Axially ChiralN‐Arylindoles via Atroposelective Cyclization of Ynamides Catalyzed by Chiral Brønsted Acids

“…Due to the acidity of the Ms group, phosphine 3 a would be obtained in 61 % yield with an e.r. of 1.5 : 98.5 upon the treatment of lithium reagent and chlorodiphenyl phosphine [15] . In addition, the PMB group was ready to be removed under mild conditions followed by oxidation, leading to axially chiral aza‐isatin 3 c in 68 % total yield with the e.r.…”

Synthesis of Stereochemically Flexible Cyclic Biphenylbisphosphinite Ligands: Control of the Dynamics and Selectivity

“…[27] Moreover, Feringa et al showed that it is possible to harness a photoresponsive catalysts (see Figure 1). [7,28,29] By introducing chiral units at the ortho positions to the central axis in the open [9] and the o-o'bridged [30] form, the atroposelective synthesis of ligands and their application could be demonstrated by Brückner and co-workers (see Figure 1). In addition to cofactor-controlled enantioselective catalysis developed and investigated by Reek and Moberg [31 -33] and helical assembly developed by Raynal [34] [35] , Breit and co-workers successfully prepared supramolecular amino acid-based PhanePhos [36] and DNA base pairinspired dynamic ligands (see Figure 1).…”