Domino Palladium-Catalyzed Double Norbornene Insertion/Annulation Reaction: Expeditious Synthesis of Overcrowded Tetrasubstituted Olefins

Abstract

A Pd-catalyzed domino process involving a double norbornene insertion/annulation reaction was developed for the expeditious synthesis of overcrowded olefins. In this one-pot reaction, four new C–C bond formations were achieved by three consecutive Heck carbopalladations and C–H activation across the CC triple bond of 2-alkynyl bromobenzenes with two norbornene rings via a reactive vinylic-Pd­(II) species. This protocol provides a step-economical synthetic system to access the structurally identical molecular machine motifs of overcrowded olefins with high yields.

Innovative Synthetic Procedures for Luminogens Showing Aggregation‐Induced Emission

“…Recently,N aveen, Perumal, and Cho extended this method to adouble norbornene insertion/annulation reaction for the rapid construction of congested tetrasubstituted olefins 4 (Scheme 1B). [32] Ther eaction showed broad substrate scope and aw ide range of substituent tolerance,w ith various twisted olefin frameworks consisting of two norbornene fragments being produced in moderate to good yields. Thef ormation of the vinylic-Pd II intermediate plays ak ey role,after which the second insertion of norbornene happens sequentially.Notably,all of the obtained olefins demonstrate pronounced AIE effects.…”

Domino Palladium-Catalyzed Double Norbornene Insertion/Annulation Reaction: Expeditious Synthesis of Overcrowded Tetrasubstituted Olefins

“…Subsequently, C would Notably, all of the synthesized overcrowded olefins displayed interesting photoluminescence (PL) properties. 15 For instance, the PL spectrum of 3k/3′k in a thin-film state showed absorption and emission maxima at 357 and 466 nm, respectively (Figure 1a). This result indicates the aggregation-induced emission (AIE) phenomenon of 3k/3′k attributed to the restriction of intramolecular motions.…”

Innovative Verfahren zur Synthese von Luminogenen mit aggregationsinduzierter Emission

“…Kürzlich erweiterten Perumal und Cho diese Methode auf den Einbau von zwei Norbornen‐Einheiten unter Anellierung zum schnellen Aufbau von tetrasubstituierten Olefinen ( 4 ; Schema 1 B). [32] Es wurden verschiedene verdrillte Olefingerüste mit zwei Norbornen‐Fragmenten hergestellt, die sich durch einen breiten Substratbereich, moderate bis gute Ausbeuten und eine hohe Toleranz gegenüber Substituenten auszeichneten. Dabei spielt die Bildung des Pd II ‐Vinyl‐Zwischenprodukts eine entscheidende Rolle; danach erfolgt der Einbau der zweiten Norbornen‐Einheit.…”