Ozone-Mediated Nitration of Phenylalkyl Ethers, Phenylacetic Esters, and Related Compounds with Nitrogen Dioxide. The Highest Ortho Substitution Observed in the Electrophilic Nitration of Arenes
摘要:
Ey the combined action of ozonized oxygen and nitrogen dioxide (the kyodai-nitration), the title compounds were smoothly nitrated in dichloromethane at subzero degrees with high ortho positional selectivity. Although the conventional nitration of phenylacetic acid and esters mainly produces m- and p-nitro derivatives, the present nitration offers a simple high-yield synthesis of o-nitro derivatives which are important as precursor in organic synthesis, The proportions of the ortho isomer in the nitration products from methyl 2-phenylethyl ether and methyl phenylacetate were 71 and 88%, respectively, the latter value being the highest ortho isomer proportion so far observed in the electrophilic aromatic nitration. The observed high ortho selectivity has been rationalized in terms of radical cation intermediate and six-membered cyclic transition state.
Saccharin sulfonic acid catalyzed N-Boc protection of amines and formation of tert-butyl ethers from alcohols
作者:F. Shirini、M. A. Zolfigol、M. Abedini
DOI:10.1007/bf03246047
日期:2010.9
(SaSA), as a stable reagent is easily prepared by the reaction of saccharin with neat chlorosulfonic acid at room temperature. This compound is able to catalyze conversion of amines to their corresponding N-Boc protected amines with (Boc)2O. Alcohols were also converted to their corresponding tert-butyl ethers. All reactions took place under mild conditions giving the desired products in good to high
microwave‐irradiated alcohol‐protecting strategy based on goldcatalysis utilizing benzyl alcohol, tert‐butyl alcohol and triphenylmethanol as alkylating reagents has been developed. This protecting strategy has wide functional group tolerance with satisfactory yields for the majority of the selected alcohols. The mechanism of this transformation was probed with oxygen‐18 isotope labelled alcohols assisted by
Zeolites are the most used catalysts worldwide in petrochemistry processes, with particular ability to stabilizecarbocations. However, the use of zeolites in organicsynthesis is still scarce. We show here that representative carboxonium-mediated organic reactions, such as the Nazarov cyclization and the tert-butylation of alcohols with tert-butyl acetate, typically performed with very strong acid
Suzuki Coupling of Potassium Cyclopropyl- and Alkoxymethyltrifluoroborates with Benzyl Chlorides
作者:Virginie Colombel、Frederik Rombouts、Daniel Oehlrich、Gary A. Molander
DOI:10.1021/jo202686p
日期:2012.3.16
Efficient Csp3–Csp3 Suzuki couplings have been developed with both potassium cyclopropyl- and alkoxymethyltrifluoroborates. Moderate to good yields have been achieved in the cross-coupling of potassium cyclopropyltrifluoroborate with benzyl chlorides possessing electron-donating or electron-withdrawing substituents. Benzyl chloride was also successfully cross-coupled to potassium alkoxymethyltrifluoroborates