Nickel(0)-Catalyzed Intramolecular [4 + 4] Cycloadditions: 5. The Type II Reaction in the Synthesis of Bicyclo[5.3.1]undecadienes

All articles of this category The preparation and type II intramolecular [4 + 4] cycloaddition of a bis-diene is described in connection with studies on the synthesis of taxol ( 1 ), crispolide ( 2 ), and vulgarolide ( 3 ). The required bis-diene is prepared by a carboalumination of an alkyne, giving an iodide which is then coupled in the presence of palladium to a vinyltin to give a stereodefined diene. Elaboration of this system involves the reaction of 2-lithio-1, 3-butadiene with a dienal to give a bis-1,3-diene tethered at the terminus of one diene and the internal position of the other. Cycloaddition of this bis-diene mediated by a nickel(0)/tri- o -biphenyl phosphite catalyst provides a bicyclo[5.3.1]undecadiene, a ring system common to a variety of complex molecules.