Cu-Catalyzed 1,2-Dihydroisoquinolines Synthesis from o-Ethynyl Benzacetals and Sulfonyl Azides

Abstract

An efficient synthesis of 1,3-/1,1-dialkoxy 1,2-dihydroisoquinolines from o-ethynylbenzacetals and sulfonyl azides via a cascade process combining copper-catalyzed alkyne-azide cycloaddition (CuAAC), Dimroth rearrangement, 1,5-OR shift/1,5-H shift, and 6π-electrocyclic ring closure (6π-ERC) is described. Extension of the produced 1,3-dialkoxy-1,2-dihydroisoquinolines to isoquinolium salts is also disclosed.

Efficient synthesis of cyclic amidine-based fluorophoresvia6π-electrocyclic ring closure

“…Increasing the reaction time to 4 h could further improve the yield to 91% (entry 8), but further increasing the reaction time to 10 h reduced the yield to 86% (entry 9). Aer screening several solvents, CHCl 3 was found to be the optimum solvent for this reaction (entries [8][9][10][11][12][13].…”

Divergent CH Insertion–Cyclization Cascades of N‐Allyl Ynamides

“…A 1,5‐hydride shift onto ketenimine H occurs in place of the 1,3‐sulfonyl shift shown to be facile with aryl ynesulfonamides 24. A 6 π electrocyclic ring closure would give the isolable heterocycles 11 / 14 25. 26 Neighboring‐group‐assisted elimination and desulfonylation would then afford 4 / 15 .…”

“…[24] A6 p electrocyclicr ing closure would give the isolable heterocycles 11/14. [25,26] Neighboring-groupassisted elimination and desulfonylation would then afford 4/ 15.Ametal catalyst could potentially play arole during each stage of this thermally viable cascade.…”

Synthesis and Photophysical Characterization of 2,3‐Dihydroquinolin‐4‐imines: New Fluorophores with Color‐Tailored Emission

“…In 2005, Chang and co‐workers have reported a highly efficient copper‐catalyzed multicomponent strategy, in which sulfonyl azides react with a wide range of alkynes and amines to form amidines . This reaction forms a highly reactive ketenimine intermediate that can be trapped with various nucleophiles and subsequently used for synthesizing various important heterocyclic structures like 4‐sulfonamidoquinolines, 1,2‐dihydroisoquinolines, 3‐aminopyrazoles, indolines, fused indolines, and 2‐imino‐3‐pyrrolines . Inspired by this ketenimine chemistry, we have reported an easier route to dihydropyrimidin‐4‐ones and β‐ and β 3 ‐amino acid analogues from propargylamides using this reactive ketenimine intermediate by an intramolecular synthetic strategy …”