Catalytic Conjugate Addition Promoted by the Copper(I)-monothiobinaphthol System
Part 2. Optimal ligand synthesis and initial catalytic results
Both racemic and (R a)-1,1′-bi-2-naphthol react with Bu 2SnO to provide an O,O-stannylene acetal which opens with Me 2NC(S)Cl or RC(O)Cl [R = Ph, CCl 3, OPr, 1-C 10H 7, 2-C 10H 7, SMe, CH 2Cl and (-)-menthyl] to fashion monoacylated derivatives. Two of the products, 2-(N,N-dimethylthiocarbamoyloxy)-2′-hydroxy-1,1′-binaphthyl 6 and 2-hydroxy-2′-[(1R,3S,5R)-menthylcarbonyloxy]-1,1′-binaphthyl 14, have been crystallographically characterised. The former is converted to 2-(N,N-dimethylcarbamoyloxy)-2′-(N,N-dimethylthiocarbamoyloxyl)-1,1′ -binaphthyl 15 with Me 2NC(O)Cl. This compound is directly available from 1,1′-bi-2-naphthol via a one-pot sequential reaction with Me 2NC(S)Cl and Me 2NC(O)Cl under NEt 3-DMAP catalysis. Thermolysis of 15 followed by hydrolysis provides an efficient preparation of 2-hydroxy-2′-mercapto-1,1′-binaphthyl 3 (monothiobinaphthol). In the presence of [Cu(MeCN) 4]BF 4, 3 leads to a highly efficient catalyst for the 1,4-addition of BuLi and RMgX (R = Me, Bu, Ph; X = Cl, Br) to cyclic enones.
S. M. Azad et al., "Catalytic Conjugate Addition Promoted by the Copper(I)-monothiobinaphthol System," Journal of the Chemical Society - Perkin Transactions 1, Royal Society of Chemistry, Jan 1997.
The definitive version is available at http://dx.doi.org/10.1039/A605620B
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