AlCl3-Mediated Aldol Cyclocondensation of 1,6- and 1,7-Diones to Cyclopentene and Cyclohexene Derivatives
摘要:
Exactly 1/3 mol of AlCl3 is sufficient to cyclize 1 mol of 1,omega-dibenzoylbutane (or pentane) to a cyclopentenone (or hexenone) derivative in high yield at room temperature in 40 min to several hours. This condensation is driven by removing elements of water as HCl and Al(OH)(3), and the product enones are exclusively unconjugated, unlike the base-catalyzed condensations providing thermodynamically more stable conjugated enones.
Direct Dehydrogenative Access to Unsymmetrical Phenones
作者:Congjun Yu、Raolin Huang、Frederic W. Patureau
DOI:10.1002/anie.202201142
日期:2022.5.9
The Friedel–Craftsreaction is an emblematic method for constructing C−C bonds at aromatic positions. Rendering this reaction dehydrogenative on a broad scope of substrates under simple reactionconditions constitutes an important milestone for synthetic chemistry.
Photochemistry of Tiaprofenic Acid, a Nonsteroidal Anti-inflammatory Drug with Phototoxic Side Effects
作者:Francisco Bosca、Miguel A. Miranda、Franklin Vargas
DOI:10.1002/jps.2600810215
日期:1992.2
The phototoxicnonsteroidalanti-inflammatorydrugtiaprofenicacid (1) is photolabile under aerobic conditions. Irradiation of a methanol solution of 1 under oxygen produces the photoproducts 2, 3, 4, and 5, and also produces a singlet oxygen as evidenced by trapping with 2,5-dimethylfuran.
A careful study of the linoleic acid hydroperoxide (LOOH) profile obtained upon peroxidation of linoleic acid (LA) photosensitized by tiaprofenic acid (TPA) and analogous ketones has been undertaken to distinguish between type-I and type-II photoperoxidation mechanisms. 1,4-Cyclohexadiene and 1,2-dimethylcyclohexa-2,5 -dienecarboxylic acid (CHDCA) have also been used as models for LA since they also have double allylic systems, Co-irradiation of LA with TPA and decarboxytiaprofenic acid (DTPA) in acetonitrile and micellar media produced significant amounts of conjugated dienic LOOH, The cis,trans to trans,trans ratio depended on the irradiation time; thus, this parameter is an ambiguous tool for mechanistic assignment. An interesting finding was the decrease of the LOOH level after long irradiation times in mixtures photooxidized by DTPA, which is attributed to quenching of the DTPA triplet by the generated dienic LOOH, High-performance liquid chromatography analyses confirmed that the main pathway operating in photodynamic lipid peroxidation sensitized by (D)TPA is a type-I mechanism. However, product studies using CHDCA have clearly shown that a type-II mechanism is also operating and might contribute to the overall photooxidation process in a significant way.