A Microwave‐Enhanced, Lewis Acid‐Catalyzed Synthesis of 1,3‐Dioxolanes and Oxazolines from Epoxides

Abstract

A fast and highly regio-and stereoselective transformation of non-conventional b-lactamcontaining epoxides into the corresponding cyclic 1,3-dioxolanes and oxazolines is herein reported, using microwave irradiation as an efficient source of energy, in the presence of stoichiometric or catalytic amounts of Lewis acids, without an additional solvent. These cyclic compounds are the protected forms of diols and amino alcohols.

CO Versus CC Bond Cleavage: Selectivity Control in Lewis Acid Catalyzed Chemodivergent Cycloadditions of Aryl Oxiranyldicarboxylates with Aldehydes, and Theoretical Rationalizations of Reaction Pathways

“…To gain some insight into the mechanistic issues raised during this study, we carried out density functional theory (DFT) studies by using oxirane 1 a and benzaldehyde 2 a as the model substrates, with SnA C H T U N G T R E N N U N G (OTf) 2 and NiA C H T U N G T R E N N U N G (ClO 4 ) 2 as the respective catalysts (see the Supporting Information for all details). [10][11][12] Both SnA C H T U N G T R E N N U N G (OTf) 2 -and NiA C H T U N G T R E N N U N G (ClO 4 ) 2 -catalyzed CÀO bond cleavages favor S N 2 stepwise pathways through an anti attack.…”

“…Zuliang Chen, [a] Ziqi Tian, [b] Jieming Zhang, [a] Jing Ma,* [b] and Junliang Zhang* [a] Oxiranes have attracted significant attention mainly as a result of being useful as building blocks for the synthesis of organic structures, their ease of preparation, and their propensity for strain-induced ring-opening reactions. The dominant chemistry of oxiranes is ring opening reactions by C À O bond cleavage, [1,2] with C À C bond cleavage as a notable exception. [3,4] Due to their unique catalytic activity, selectivity, and reactivity under mild conditions, Lewis acids have been developed as an essential tool for synthetic transformations, and have been widely used in the synthesis of natural products and medicinal compounds.…”

“…Moreover, (Table S1, entries 10 and 12) are classified into group B-3. The reaction proceeded slowly 2 , AgOTf, or AgClO 4 ·H 2 O was used as the catalyst, and these catalysts are classified into group C (Table S1, entries 6-9, 33).…”

The Cycloaddition Reaction Between α‐Bromo Vinylketenes and Imines: A Combined Experimental and Theoretical Study

“…Moreover, these heterocycles are suitable for further manipulations that involve the substitution of the halogen atom and the transforma-tion of the double bond. [57][58][59][60][61][62][63] Furthermore, it is interesting to note that derivatives of 3-bromo-3-alkenyl-A C H T U N G T R E N N U N G azetidin-2-ones and 3-bromo-4-alkyl-5,6-diyhdropyridin-2-ones have been shown to behave as inhibitors of the ACAT enzyme and antagonists of a V b 3 and a 5 b 1 integrins, respectively. [64][65][66][67] Herein we report an advanced investigation on the synthesis of four-and six-membered lactams via cycloaddition reactions between a-bromo vinylketenes and imines.…”

Palladium-catalysed arylative cyclisation of N-allylacetamides with aryl halides yielding benzyl-substituted oxazolines

“…Oxazoline 2a was converted to acetamide 13 by acidic hydrolysis with trifluoroacetic acid. 13 The overall transformation of 1a to 13 represents regioselective carbohydroxylation of N-allylacetamide.…”