ChemInform Abstract: Catalytic Conjugate Addition Promoted by the Copper(I) Monothiobinaphthol System. Part 3. Comparison of Three Thiolate-Based Catalytic Systems.

Monothiobinaphthol (MTB, 2-hydroxy-2'-mercapto-1,1'-binaphthyl undergoes S-alkylation with BuBr and alpha,omega-dihalides to afford thioether species. The precursor to MTB, 2-(N,N-dimethylcarbamoyloxy)-2'-(N,N-dimethylcarbamoylthio)- 1,1'-binaphthyl, undergoes anionic Fries rearrangement of the O-aryl carbamate to afford a crystallographically characterised amido species. Hydrolysis of this species affords the 3-C(O)NMe2 analogue of MTB. These MTB-based ligand systems have been tested in asymmetric conjugate addition reactions of cyclic and acyclic enones and compared with 1,1'-bi(2-thionaphthol). Active catalysts are formed in all cases but only low enantioselectivities are realised (0-55% ee). Full conditions for the separation of the enantiomeric conjugate addition products are reported.