328917-31-3Relevant academic research and scientific papers
Towards asymmetric catalysis in the major groove of 1,1′-binaphthalenes
Lustenberger, Philipp,Diederich, Francois
, p. 2865 - 2883 (2007/10/03)
Four new diphosphane ligands, (R)-4, (R)-5, (S)-6, and (R)-7 (Schemes 3, 4, 6, and 7), featuring metal-coordination sites located in the major groove of chiral 1,1′-binaphthalene clefts, were prepared in enantiomerically pure form. The performance of this new class of ligands was tested in enantioselective, Pd-catalyzed allylic alkylation reactions with acyclic and cyclic methyl carbonates 28-30 as substrates under various reaction conditions (Schemes 8 and 9). Using sodium phenyl sulfinate as a nucleophile, the reactivity of the catalysts formed with the new ligands and suitable palladium precursors was found satisfactory (> 90%); however, the ee values were in all cases poor (31P-NMR-Spectroscopic investigations revealed the formation of multiple-catalyst species in solution (Fig. 2), and molecular modeling suggested a lack of embedding of the coordinated substrate in a 'chiral pocket' (Fig. 3), which probably accounts for the observed low level of enantioselectivity.
