Novel Use of Selectfluor^TM for the Synthesis of cis‐Fused Pyrano‐ and Furanotetrahydroquinolines

Abstract

Aryl imines formed in situ from aryl aldehydes and aromatic amines undergo smooth [4 2] cycloaddition reactions with cyclic enol ethers such as 3,4-dihydro-2H-pyran and 2,3-dihydrofuran in the presence of 10 mol % Selectfluor TM in acetonitrile at room temperature to afford pyrano-and furanotetrahydroquinoline derivatives in excellent yields with high endo-selectivity.

Friedel‐Crafts‐Type Reaction of (Het)Arenes with Aldehydes/Ketones under Acid‐Free Conditions using Neutral Ionic Liquid: A Convenient Routes to bis(Indolyl)methanes and Beyond

“…Nevertheless, it has been suggested in the literature that the methylation at C 2 ‐position increases the stability of imidazolium cation via the hyper‐conjugation effect between H‐atom of methyl group and imidazole ring [30,31] . Unlike reported previously with ionic liquids, [18a,b] the cation−π interaction between indole and imidazolium cation has not been observed in the present case, probably due to presence of methyl at C2 carbon of NIL; See Figures S1 and S2 for enthalpy and Gibbs energy changes during catalytic cycle. Also, the stepwise interaction of NIL with 1 a is endergonic and hence not favorable.…”

The α-chymotrypsin-catalyzed Povarov reaction: one-pot synthesis of tetrahydroquinoline derivatives

“…5 Among the currently available synthetic methodologies, the Povarov reaction, 6 an inverse electron-demand aza-Diels-Alder reaction between N-aryl imines and electron-rich olefins, is one of the most facile and synthetically practical approaches to the synthesis of tetrahydroquinolines in high structural diversity. A series of Lewis acids such as GdCl 3 , 7 SmI 2 , 8 lanthanide complexes, 9 chiral phosphoric acid, 10 and Selectfluor 11 have been used as efficient catalysts for this reaction. However, many of these catalysts are not fully satisfied with operational simplicity and mild reaction conditions, and some of the catalysts suffer from disadvantages such as expensiveness, moisture sensitivity, multistep synthesis, and toxicity to the environment and humans.…”

Bi-functionalized PEG1000 ionic liquid [Imim-PEG1000-TEMPO][CuCl2−]: an efficient and reusable catalytic system for solvent-free aerobic oxidation of alcohols

“…Room temperature ionic liquids (RTILS) have drawn increasing studies over the last few decades due to excellent advantages like negligible volatility, thermal stability, remarkable solubility and a variety of available structures. [26][27][28][29][30] Notably, functionalized ILs for specific-task have drawn much interest in the synthesis fields. In 2005, Miao 31 et al reported an effective catalytic system comprising 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO) functionalized imidazolium salt ([Imim-TEMPO] + X À ), a carboxylic acid substituted imidazolium salt ([Imim-COOH] + X À ), and sodium nitrite (NaNO 2 ) which was developed for the aerobic oxidation of aliphatic, allylic, heterocyclic and benzylic alcohols to the respective carbonyl compounds with an excellent selectivity of up to 499% under ambient conditions.…”