F. Dean Toste of the University California developed an efficient methodology for highly substituted furans via the copper(II) catalytic enantioselective indole addition reaction.
Optimization: treated with Ag(I)catalyst under various temps.the ee% value was not beyond 74%.So Cu(I) and Cu(II) were tested ,they found Cu(I) catalytic product was unable to enhance the enantioselectivity lowering the temp..but Cu(II) did !
Mechanism: