Catalytic conjugate addition promoted by the copper(I)-monothiobinaphthol system .2. Optimal ligand synthesis and initial catalytic results

Both racemic and (R(a))-1,1'-bi-2-naphthol react with Bu(2)SnO to provide an O,O-stannylene acetal which opens with Me(2)NC(S)Cl or RC(O)Cl [R = Ph, CCl3, OPr, 1-C10H7, 2-C10H7, SMe, CH2Cl 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)-menthylcarbonyloxyl]-1,1'-binaphtyl 14, have been crystallographically characterised. The former is converted to 2-(N,N-dimethylcarbamoyloxy)-2'-(N,N-dimethylthiocarbamoyloxy)-1,1'-binaphthyl 15 with Me(2)NC(O)Cl. This compound is directly available from 1,1'-bi-2-naphthol via a one-pot sequential reaction with Me(2)NC(S)Cl and Me(2)NC(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)]BF4, 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.