Multicomponent Coupling Reaction and Intramolecular Nitrile Oxide–Alkyne Cycloaddition towards Isoxazolo[3,4]‐pyrrolizines

Abstract

This study reports an efficient four-step method to synthesize as eries of new (4S,8aS)-3,4-diphenyl-6,7,8,8a-tetrahydro-4H-isoxazolo[3,4-a]pyrrolizines. The first step involves ac opper(II) acetylacetonate catalyzed three component coupling of aldehyde, (S)-pyrrolidin-2-ylmethanol, and alkynes (A 3 coupling) to form propargylamines (4a-4n). The coupling reaction is applicable to various aldehydes,a mines, and alkynes and provides the propargylaminesi ng ood to excellent yields with excellent distereoselectivities. Products (4a-4n)w erec onvertedi nto aldehydes( 5a-5n)b yS wern oxidation, aldehydes (5a-5n)w ere reacted with hydroxyl amine hydrochloride to form aldoxime( 6a-6n), respectively. Further aldoximes (6a-6n)u nderwent an intramolecular 1,3dipolar cycloaddition to form tricyclic-fused isoxazoles (7a-7n). The1 ,3-dipolar cycloaddition reaction tolerates high structurald iversity and generated desired products (7a-7n) in moderate to good yields and excellentd iastereoselectivities. Ap roposed mechanism for synthesis of 7a is reported.[a] S.

Photocatalytic Aryl Sulfide Oxidation Using 4-Nitrophenylacetylene-Modified Cu2O Crystals

“…33 The carbonate anion then removes the acidic terminal proton to generate a highly reactive acetylide anion, which directly reacts with a surface Cu(I) atom to give the copper acetylide complex. 34 The successful 4-NA functionalization on Cu 2 O cubes and rhombic dodecahedra can be verified using FT-IR characterization (Figure 2). For 4nitrophenylacetylene, the high-intensity peak at ν̃= 3248 cm −1 is the characteristic signal of terminal alkyne, originated from sp C−H bond stretching.…”

“…First, 4-NA forms a π-alkyne complex with the Cu­(I) cation, which enhances the acidity of the alkyne proton . The carbonate anion then removes the acidic terminal proton to generate a highly reactive acetylide anion, which directly reacts with a surface Cu­(I) atom to give the copper acetylide complex . The successful 4-NA functionalization on Cu 2 O cubes and rhombic dodecahedra can be verified using FT-IR characterization (Figure ).…”

Copper‐Catalysed Multicomponent Syntheses of Heterocycles

“…Afraj and co‐workers developed an efficient copper(II) acetylacetonate catalysed three‐component A 3 coupling reaction of ( S )‐pyrrolidin‐2‐ylmethanol, aldehyde and alkynes to form propargylamines which on intramolecular 1,3‐dipolar cycloaddition yielded a series of new (4S,8aS)‐3,4‐diphenyl‐6,7,8,8a‐tetrahydro‐4 H ‐isoxazolo[3,4‐ a ]pyrrolizines . The initial optimized reaction for A 3 coupling include benzaldehyde (1 equiv.…”