Chemoselectivity in SN2-E2 reactions induced by aqueous association colloids

The effects of cationic and sulfobetaine surfactants and quaternary ammonium salts upon the products of S(N)2 and E2 reactions of sulfonate esters have been examined in mixtures of bromide and hydroxide ions. Surfactants are: n-C16H33N+R3X-, R=Me, Et, n-Pr, n-Bu, X=Br, OH, OMs; n-C14H29N+Me2(CH2)(3)SO3- and salts were R4NBr, R=Me, n-Bu. Without surfactants the reaction of OH- is dominant, but with surfactants the reaction of Br- generates alkyl bromides, and selectivity is largest with n-C16H33N+Bu3Br-. Elimination is favored relative to substitution by OH-. Most reactions were made with 10(-3) M substrate, but scale-up to 10(-2) M substrate was successful in hexane-water with extraction of the products and re-use of the aqueous surfactant. (C) 1998 Elsevier Science B.V.