High-Pressure Organic Chemistry. 19. High-Pressure-Promoted, Silica Gel-Catalyzed Reaction of Epoxides with Nitrogen Heterocycles^1,

Abstract

The reaction of epoxides with nitrogen heterocycles such as indoles, pyrroles, imidazoles, and pyrazoles was studied under both high-pressure and silica gel-catalyzed conditions. Whereas it has been reported that the treatment of indole with styrene oxide at 10 kbar and 42 °C for 24 h gave 2-(3-indolyl)-2-phenylethanol in 56% yield, the same compound was obtained in 88% yield when the reaction was conducted on silica gel at rt for 1 week. Similarly, efficient reaction of epoxides with pyrroles, imidazoles, and pyrazoles was achieved. In terms of stereochemical features, the epoxide ring opening reaction of (R)-(+)-styrene oxide with indole was found to proceed stereoselectively in an SN2 fashion at the benzyl carbon, in either case.

Physical and chemical interactions between bile pigments and polyaromatic mutagens

“…found that 88% of 5.12 was converted to 2-(3'-indolyl)-2-phenylethanol (5.13), however they do not report any other minor products. 234 Similarly, we found 5.13 to be the major product of our reaction between 5.7 and 5.12, being isolated in 80% yield but the overall yield of conjugates from the reaction was 97% with the remaining 17% being made up of minor products resulting from attachment of 5.7 to other sites around the heterocycle. GC/MS, one-and two-dimensional NMR spectroscopy, TLC, LRESIMS, HRESIMS, and melting point analysis were used to identify eight products from the reaction of 5.7 and 5.12.…”

“…76 Addition of silica to the reactions as a catalyst had a crucial role in activating 5.7 to nucleophilic attack, 232,233 replacing the hydrogen bonding role of water molecules in an aqueous medium. 234 The experiments aimed to assess the reactivity of the pyrrole ring, as well as other nitrogen containing aromatic rings, toward activated epoxides. They represented preliminary examination of the mechanism of reactions that may contribute to the inhibition of mutagenic epoxide agents by natural BPs.…”

Regioselective ring opening of 2,2-dicyanooxiranes by 1,3-dinucleophiles in the presence of Lewis acids such as bismuth(III) nitrate pentahydrate [Bi(NO3)3·5H2O] and zirconium(IV) chloride (ZrCl4)

“…The requirement for high temperature in epoxides sensitive to this condition led to the necessity for activation of the epoxide rings to increase their susceptibility to nucleophilic attack. The various methodologies developed for this purpose include the use of Lewis acid catalysts such as alumina [7], metal triflates [8], transition-metal halides [9], alkalimetal perchlorates [10], silica under high pressure [11], and montmorillonite clay under microwave irradiation [12]. The search for new and efficient Lewis acid catalysts for various useful organic transformations is one of the most important, interesting, and challenging research topics in catalytic synthesis.…”

H14[NaP5W29MoO110]: a Novel and Useful Catalyst for Aminolysis of Epoxides with Amines under Solvent‐Free Conditions

“…2 The nucleophilic ring-opening of epoxides with an amine is recognized as an important route to obtain β-amino alcohol with 1,2-trans stereochemistry. Therefore, various methodologies have been developed for this purpose, which include the use of alumina, 3 metal alkoxides, 4 metal triflates, [5][6][7] transition metal halides, 8 alkali metal perchlorates, 9 rare earth metal halides, 10 silica under high pressure, 11,12 and montmorillonite clay under microwave irradiation. 13 However, these methodologies suffer from one or more disadvantages such as long reaction time, high reaction temperature, moderate yield, use of air or moisture sensitive catalysts, and requirement of the stoichiometric amount of catalyst.…”