Patent ID: 8835658

Claim:
A method of synthesizing norcantharidin analogues comprising the structure of compound 5: wherein R 1 , R 2 , R 3 , R 4 are selected from the group consisting of hydrogen, halogen, alkyl, alkenyl, alkynyl, hydroxyl, alkoxyl, amine, nitro, alkylthio and heteroalkyl, and wherein R 5 , R 6 , R 7 , R 8 , R 9 are selected from the group consisting of hydrogen, halogen, alkyl, alkenyl, alkynyl, hydroxyl, alkoxyl, amine, nitro, nitrile, alkylthio, trifluoromethyl, alkyl sulfonyl and aryl sulfonyl, the method comprising the step of alkynylation of oxabenzonorbornadienes in the presence of a catalyst including a transition metal compound and a biaryl diphosphine ligand selected from the group consisting of: