Palladiumkatalysierte C‐H‐Alkinylierung unaktivierter Alkene

Abstract

Es wird über eine palladiumkatalysierte regio-und diastereoselektive C-H-Funktionalisierung mit Bromalkinen und elektronisch nicht aktivierten Olefinen berichtet. Die Picolinamid-Gruppe ermçglicht die Bildung von 5-und 6-exo-Metallazyklen als Intermediate, die stereospezifisch monoalkinylierte Produkte in bis zu 91 % Ausbeute liefern. Die systematische Studie zeigt, dass Substrate mit einem breiten Spektrum von Substituenten an den Olefin-und Bromalkin-Kupplungspartnern kompatibel sind. Chemoselektive Transformationen wurden für die erhaltenen Amide, Olefine und Alkine gezeigt.

1‐Phospha‐Butadienes and 1H‐Phospholes via Alkynylation of Acetylenic Phosphaalkenes

“…Despite a lack of a mechanistic proposal, similarities of reaction conditions and the observed stereo‐ and regio‐selectivity suggest an analogous mechanism in the formation of these carbon diene‐yne derivatives. Similarly, Pd‐mediated C−H activation in ethene fragments using directing groups has been achieved illustrating the necessity of heteroelement donor sites (Figure 3 iii) [20] …”

Picolinamides and Iodoalkynes Enable Palladium‐Catalyzed syn‐Aminoalkynylation of Di‐ and Trisubstituted Alkenes to Give Pyrrolidines

“…To demonstrate this, picolinamidedirected CÀ H functionalization was used for the preparation of di-and trisubstituted olefins (Scheme 4). Through the use of our method developed for CÀ H alkynylation of olefins, [6] alkene 12 was accessed from 1 g in 76 % yield. Enyne 12 then undergoes aminoalkynylation to yield highly functionalized pyrrolidine 13 as a single diastereomer (72 %).…”

“…[9] Following the pioneering research of Engle's group on the use of bidentate directing groups in the hydroamination of unactivated alkenes, [10] a multitude of related olefin functionalizations have been reported. [11] Bishomoallylic picolinamides were demonstrated to be suitable substrates for alkene CÀ H activation, [6,12] directed Heck reactions, [6] 1,2difunctionalization, [13] and hydrofunctionalization reactions (Scheme 1D). [14] However, to the best of our knowledge no systematic study utilizing the picolinamide as both an auxiliary and a coupling partner for alkene 1,2-difunctionalization has been reported to date (Wu's group reports a single example using the picolinamide group during reaction-optimization of an aminocarbonylation reaction, affording the target compound in 26 % yield [11h] ).…”

“…During our previous studies on Pd-catalyzed picolinamide-directed CÀ H alkynylation of olefins [6] we observed that the use of bromoalkynes as coupling partners was essential for formation of products resulting from CÀ H activation (see Supporting Information). Over the course of our investigations, we observed that the use of the corresponding iodoalkyne provided a different set of products, namely the pyrrolidines resulting from an aminoalkynylation reaction.…”