A novelsyntheticmethod of ketodiphenylselenonium ylide from alkynylselenonium salt is described. A reaction of alkynylselenonium salt, hydroxide ion, and aldehyde in the presence of silver triflate and triethylamine gave oxiranylketones just as a trans-isomer in moderate to good yields, whereas benzoyl aziridine derivatives were obtained from the reaction with sodium p-toluenesulfonamide instead
The treatment of alkynylselenonium salt with benzenesulfinic acid in iPrOH gives (Z)-β-sulfonylvinylselenonium salts in good yields. The alkenylselenonium salts thus prepared react with nucleophiles such as alkoxides, halides, and acetylides to produce β-functionalized (Z)-vinyl sulfones in high yields. Furthermore, we succeeded in the simple stereoselective one-step synthesis of various chiral (Z)-β-alkoxyvinyl sulfones by the use of chiral alcohols.
Alkynylselenonium salts 2 and 5 were synthesized and treated with benzenesulfinic acid or its sodium salt in an alcohol. The reactions with sodiumbenzenesulfinate gave (Z)-β-alkoxyvinylsulfones 6 as main products, while the reactions with benzenesulfinic acid afforded the β-sulfonylvinylselenonium salts 11 and 12 in good yields.
The reaction of diphenyl(phenylethynyl)selenonium salt 1a with 1.0 equiv. of phenyllithium afforded 1,4-diphenylbutadiyne 5 and 1-(o-biphenylyl)-2-phenylethyne 7 in 25% and 15% yields, respectively. The latter product 7 was formed via the benzyneintermediate.
The reactions of alkynylselenonium salts with n-Bu4NX (X = I, Br, CI) in CH2Cl2 gave 1-halo-1-alkynes or phenacyl halide derivatives and selenide, while the reaction with F-. afforded a terminal alkyne and a selenoxide. Seemingly, the selenonium salts acted as alkynyl cations in the former case and as alkynyl anions in the latter case. (C) 1999 Elsevier Science Ltd. All rights reserved.