Olefins by the Wittig reaction
Brevet
Olefins of the formula R1XC:CR2R3 were prepd. by removal of a proton from a betaine-like intermediate, (Ph)3P+-CHR1CR2R3O-, and subsequent treatment with the desired X+. Thus, 1 mole PhLi and the phosphonium salt, (Ph)3PCH2R1.HCl, in 3 parts Et2O and 1 part tetrahydrofuran at 0 Deg was treated with 1 mole of the carbonyl compd., R2COR3. The intermediate, at -20 Deg, was then treated with a 2nd mole of PhLi, and after 30 min., 1 mole of X-Y was added to give the desired olefin. In some cases, 1.5 mole KOBu-tert was added to accelerate the reaction with X-Y. The olefins prepd. and the X-Y compd. used were (R1, R2, R3, X-Y, % yield, and b.p./mm. given): H, Ph, H, DCl, 50, 60-70 Deg/0.6; Me, Ph, H, DCl, 52, 60-5 Deg/0.14; H, Ph, H, MeI, 10, 180-2 Deg/760; Me, Ph, H, MeI, 55, 64-7 Deg/0.14; Me, Ph, H, FClO, 37, 85-100 Deg/0.70; H, Ph, H, Cl2IPh, 33, 86-8 Deg/0.12; Me, Ph, H, Cl2IPh, 60, 90-6 Deg/-0.60; Me, Ph, H, N-bromosuccinimide, 18, 97-104 Deg/0.12; Me, Ph, H, Br2 , 23, 152-6 Deg/0.12; Pr, Et, H, FClO3 , 61, 90-110 Deg/-760; Pr, Et, H, Cl2IPh, 68, 156-62 Deg/760; Me, Ph, H, ClCO2Me, 15, 110-25 Deg/0.12; Et, Ph, H, MeI, 30, 105-9 Deg/0.12. [on SciFinder (R)]