Novel chiral C₁- and C₂-symmetric chelating phosphine catalyst-ligands with rigid aromatic backbones (1,2-phenylene and 1,8-naphthalene) were developed and checked by both allylic Pd-catalysed stereoselective substitution and Rh(I)-catalysed hydrogenation reaction. Furthermore, 1,2-bisphosphinoacenaphtylenes and -acenaphtenes were synthesized.
Chiral C₁-symmetric 1-diphenylphosphino-2-phospholanobenzenes were obtained by consecutive metallation and alkylation of the novel 1-diphenylphosphino-2-phosphinobenzene.
A chiral C₂-symmetric P,P-ligand was synthesized by twofold lithiation of 1,8-dibromonaphthaline and subsequent reaction with the chiral (2R,5R)-1-chloro-2,5-dimethylphospholane. P,N-ligands bearing either chiral phospholane or chiral phosphetane moieties were obtained from the novel primary 1-dimethylamine-8-phosphinonaphthaline by consecutive metallation and alkylation. Various P,N-ligands containing a chiral (2R,5R)-2,5-dimethylpyrrolidine moiety were accessible from the novel 1-bromo-8-((R,R)-α’-dimethylpyrrolidino)naphthalene by lithiation and subsequent phosphination with various chlorophosphines.
1,2-bisphosphinoacenaphthylenes were synthesized by twofold lithiation-phosphination of 1,2-dibromoacenaphthylene with the corresponding chlorophosphines. Reduction of bis(diphenylphospino)acenaphthylene with zinc in acetic acid afforded cis-bis(diphenylphosphino)acenaphthene.