various para- and meta-substituted aromatic bromides, mostly bearing sensitive moieties, with several carboxylic acid anhydrides is reported. This reaction can be carried out in two steps, by forming an aromatic organozinc reagent via cobalt catalysis in the first step, or even more interestingly in a single step, also by using a cobalt-based catalyst. The aromaticketones are obtained by these new, mild
atom efficient ‘trifluoroacetic ester/ketone metathesis’ has been sincerely witnessed. Enolizable alkyl (at least two non-hydrogen atoms) aryl ketones were found to react readily with ethyl trifluoroacetate under the promotion of NaH to afford trifluoroacetic ester/ketone exchange products, trifluoromethyl ketones (TFMKs), and aromatic acid esters, which were quite different from the general Claisen
The direct formation of functionalized alkyl(aryl)zinc halides by oxidative addition of highly reactive zinc with organic halides and their reactions with acid chlorides, .alpha.,.beta.-unsaturated ketones, and allylic, aryl, and vinyl halides
作者:Lishan Zhu、Richard M. Wehmeyer、Reuben D. Rieke
DOI:10.1021/jo00004a021
日期:1991.2
Highly reactive zinc, prepared by the lithium naphthalenide reduction of ZnCl2, readily undergoes oxidative addition to alkyl, aryl, and vinyl halides under mild conditions to generate the corresponding organozinc compounds in excellent yields. Significantly, the reaction will tolerate a spectrum of functional groups on the organic halides. Accordingly, this approach can now be used to prepare a wide variety of highly functionalized organozinc compounds. In the presence of Cu(I) salts, the organozinc compounds cross-couple with acid chlorides, conjugatively add to alpha,beta-unsaturated ketones, and regioselectively undergo S(N)2' substitution reactions with allylic halides. They also cross-couple with aryl or vinyl halides with Pd(0) catalysts.
PYRAZOLE DERIVATIVES, COMPOSITIONS CONTAINING SUCH COMPOUNDS AND METHODS OF USE