Isopropenyltriphenylphosphonium Bromide is used as a Michael-Wittig combinatorial reagent for preparation of 2-methyl allylic ethers, 3-methyl-2H-1- benzopyrans, 3-methyl-2-cyclopentenones, 3-methyl-2,5-dihydrothiophenes, and 1- methyltricyclo[3.2.1.02,7]octan-6-ones.
Isopropenyltriphenylphosphonium Bromide is synthesized by fusion of Triphenylphosphine with anhydrous Nickel(II) Bromide followed by addition of dry benzonitrile and azeotropic removal of the residual water, addition of 2- bromopropene, and heating of the resultant mixture from 50-80 °C to 200 °C over a period of 2 d.Workup includes steam distillation to remove benzonitrile, filtration of a black insoluble material, and extraction of the filtrate with CH2Cl2. After drying and concentration at reduced pressure, the crude solid thus obtained is purified by recrystallization from CH2Cl2-EtOAc.1
