Chromium(II)-Mediated Reactions of Iodonium Tetrafluoroborates with Aldehydes: Umpolung of Reactivity of Diaryl-, Alkenyl(aryl)-, and Alkynyl(aryl)iodonium Tetrafluoroborates
作者:Da-Wei Chen、Masahito Ochiai
DOI:10.1021/jo990809y
日期:1999.9.1
of iodonium salts with anhydrous chromium dichloride, followed by their nucleophilic addition to aldehydes to yield alcohols. In contrast to the reaction of aryl and alkenyl halides with chromium dichloride, these iodonium salts are so active that organochromium(III) could be generated without using a nickel catalyst. Substituent effects of unsymmetrically substituteddiaryliodoniumsalts on the product
Reactions of vinylsilanes with lewis acid-activated iodosylbenzene: stereospecific syntheses of vinyliodonium tetrafluoroborates and their reactions as highly activated vinyl halides
salts behave like the highly activated species of vinyl iodides due to the high leaving ability of the iodine(III) substituents. Thus, a variety of substituted olefins including α-cyano and α-nitro olefins, vinyl sulfides, vinyl halides, and α,β-unsaturated esters, were synthesized from under mild conditions. A ligand coupling mechanism via the formation of 10-I-3 intermediate containing a copper(III)
mainly from the halo-λ3-iodane intermediate; the substitution occurs as a bimolecular reaction with the external halideion while the elimination is a unimolecular (intramolecular) reaction. The intermediacy of the hypervalent λ3-iodane as well as of the iodate are also confirmed by UV spectroscopy. The secondary kinetic isotope effects, leaving group substituenteffects, and pressure effects on the
One-Pot Transformation of RCHO to (<i>E</i>)-RCH=CHSiMe<sub>3</sub> Using CHI<sub>3</sub>, Mn, Me<sub>3</sub>SiCl, and a Catalytic Amount of CrCl<sub>2</sub>
Iodoform is reduced with manganese in the presence of Me3SiCl to give Me3SiCHI2 (1). A one-pot transformation of aldehydes to (E)-1-alkenyltrimethylsilanes is then performed with iodoform, manganese, Me3SiCl, and a catalytic amount of chromium(II) chloride in THF via in situ formation of 1.
Réaction de quelques allènes avec l'hydrure de di-isobutyl-aluminium
作者:Michel Montury、Jacques Goré
DOI:10.1016/s0040-4039(00)93622-0
日期:1980.1
Reduction of the more substituted of the two double bonds of the allenic linkage can be selectively achieved by the reaction with DIBAH followed by hydrolysis.