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

An asymmetric methanolysis of glutaric anhydride and 6 ensuing steps gave veratrol-annulated dimethylcyclo-heptenone 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−NH2 underwent Fischer indole syntheses providing the tetracyclic indoles cis- and trans-14a, respectively. Double lithiations with BuLi and quenchings with ClPPh2 furnished the diphosphanes cis- and trans-15 with perfect (P)- and (M)-atropselectivity, respectively.