Synergistic catalysis is a specialized approach to catalysis whereby at least two different catalysts act on two different reactive sites simultaneously to facilitate chemical reactions.The traditional synthesis methods of high-strained bicyclo[3.n.1]system generally suffered from low selectivities or inaccessibility of substrates.In these methods,the Conia-Ene reaction is an intramolecular,thermal or Lewis acid-catalysed reaction of unsaturated carbonyl compounds to yield cyclised products.However,mono-ketone substrates proceeded at much harsher reaction conditions.Recently,we developed a highly efficient and practical metal/proton-synergistically catalyzed Conia-Ene reaction for the synthesis of bicycle [3.n.1] alkanones(n = 2-9).Owing to the excellent substrate scope and mild reaction condition,this synergistic catalytic system holds considerable potential in the construction of complex molecules.In particularly,this synergistic catalysis was successfully utilized in modifying the nature compounds,such as methyl dihydrojasmonate,ɑ,β-thujone,and 5α-cholestan-3-one.Furthermore,the bridged-carbonyl group of bicyclo[3.2.1]-alkanones could be easily attacked by the nucleophiles to give the ring-opening product cycloheptenones or bicycle[4.2.1]amide in excellent yields(Scheme 1).