Scheme 16.

Transfer hydrogenative diene-diol [4+2] cycloaddition.a
aYields are of material isolated by flash chromatography on silica gel. dppp = bis-(diphenylphosphino)propane. BINAP = 2,2′-bis-(diphenylphosphino)-1,1′-binaphthalene. dppPh = bis-(1,2-diphenylphosphino)benzene.