The Photochemistry of Methoxy-Substituted Benzyl Acetates and Benzyl Pivalates: Homolytic vs Heterolytic Cleavage
摘要:
The multiple methoxy-substituted benzyl acetates (3g-i) and benzyl pivalates (4g-i) have been photolyzed in methanol solution. The products of these reactions are derived from two critical intermediates; the benzyl radical/acyloxy radical pair and the benzyl cation/carboxylate anion pair. As predicted by the meta effect, the yield of ion-derived product, the methyl ether in this case, was enhanced by the presence of the m-methoxy groups. The yield of ether, for the acetate esters, varied from 2% for the 4-methoxy-substituted ester to 66% for the 3,4,5-trimethoxy-substituted ester. In contrast, the yield of ether, for the pivalate esters, varied from <1% for the 4-methoxy-substituted ester to 20% for the 3,4,5-trimethoxy-substituted one. The meta effect does not explain these differences; electron transfer converting the radical pair to the ion pair is still an important pathway in the mechanism for ion formation. A quantitative analysis of the yield of the ethers was done in order to obtain the electron-transfer rate constants. This analysis revealed that the yield of the ethers was higher than expected based on previous results for other substituted benzyl acetates. A possible explanation for this discrepancy is that internal return of the radical pair to starting material for the acetate esters is more efficient than for the pivalate esters. Also, the esters 3k and 3l, were prepared to study the effect of electron-withdrawing groups in the meta position. For these esters, the benzylic cleavage reactions were inefficient and an isomerization reaction, the benzvalene rearrangement, was competitive.
An approach to heterodiarylmethanes via sp2–sp3 Suzuki−Miyaura cross-coupling
作者:Gavin W. Stewart、Peter E. Maligres、Carl A. Baxter、Ellyn M. Junker、Shane W. Krska、Jeremy P. Scott
DOI:10.1016/j.tet.2016.02.030
日期:2016.6
The synthesis of a range of structurally diverse diarylmethanes via the Suzuki−Miyaura cross-coupling of aryl methane acetates and arylboronicacids is reported, including several challenging examples containing nitrogen, oxygen and sulfur heteroatoms in one or both coupling partners. A single set of optimized conditions was used to generate the diarylmethanes in 52–91% yield.
This invention relates to a range of alpha substituted 2-benzyl substituted imidazole compounds and pharmaceutically acceptable salts and solvates thereof, to compositions comprising such compounds, processes for their synthesis and their use as parasiticides.
Cyanothiophene derivatives, compositions containing such compounds and methods of use
申请人:——
公开号:US20040097557A1
公开(公告)日:2004-05-20
The present invention addresses substituted cyanothiophene derivatives of the formula I:
1
as well as compositions containing such compounds and methods of treatment. The compounds in the present invention are glucagon antagonists. The compounds block the action of glucagon at its receptor and thereby decrease the levels of plasma glucose providing a treatment of diabetes.
An industrially advantageous process for producing cyanobenzyl compounds under mild conditions from relatively easily available cyanobenzylamine having a cyano group on the benzene ring or a compound thereof which is ring-substituted with a chlorine atom, a fluorine atom, etc. The process for producing a cyanobenzyl compound includes transforming an aminomethyl group of a cyanobenzylamine compound into a hydroxymethyl group, a halogenomethyl group, or an acyloxymethyl group without causing damage to a cyano group on the benzene ring. The transformation may be carried out by use of nitrosonium ions.
This invention relates to a range of 1-aryl-4-cyclopropylpyrazoles in which the cyclopropyl ring is substituted at the angular position, and pharmaceutically acceptable salts and solvates thereof, to compositions comprising such compounds, processes to their synthesis and their use as parasiticides.