Cross‐Coupling Reactions to sp Carbon Atoms

Aus der Sicht des Synthetikers: Palladiumkomplexe N‐heterocyclischer Carbene als Katalysatoren für Kreuzkupplungen

“…[200,201] Das wichtigste Reaktionsprotokoll nutzt Kupfersalze als Cokatalysatoren, meistens in Gegenwart von Aminbasen (Sonogashira-Reaktion). [201] [202] Unerwartet zeigte SIPr·HCl (13, Tabelle 1) nur moderate Aktivität.…”

FRET‐Nachweis geometrisch präzise definierter Expansions‐Kontraktions‐Bewegungen im Multinanometerbereich eines Resorcin[4]aren‐Cavitand‐basierten Schalters

“…70 ) Zustand (Abbildung 1), was die eindeutige Beobachtung unterschiedlichen FRET-Verhaltens in beiden Zuständen ermöglichen sollte. [16a] Die Synthese von 1 erfolgte in hochkonvergenter Weise: Sonogashira-Kreuzkupplung [18] (über 9!10!11) zur Acceptorkomponente 12 (Schema 1).…”

Efficient Synthesis of 2‐Substituted Indoles Based on Palladium(II) Acetate/Tri‐tert‐butylphosphine‐Catalyzed Alkynylation/Amination of 1,2‐Dihalobenzenes

“…This possible route appeared to be very attractive considering: (a) due to the electronic nature of alkynyl groups, o-alkynylhalobenzenes are expected to be more reactive than strong deactivating amino group-containing o-haloanilines, and are thus expected to behave similarly like other o-substituted halobenzenes for the Buchwald-Hartwig aminations [6] and (b) o-alkynylhalobenzenes, especially o-alkynylchlorobenzenes, have been well-established to be readily accessible from the monoalkynylation of 1,2-dihalobenzenes. [7,8] Based on the fact that enormous progress has been achieved in Pd(0)-catalyzed amination reactions in recent years and different types of aryl halides including aryl chlorides have been demonstrated as suitable substrates, [6,9] we believed that the amination of o-alkynylhalobenzenes including o-alkynylchlorobenzenes could be possible and the strategy of alkynylation followed by amination of 1,2-dihalobenzenes would provide us an efficient and general method to access 2-substituted indoles.[10] Herein our results are reported. …”

“…[10] Herein our results are reported. Although the monoalkynylation of 1,2-dihalobenzenes with terminal alkynes to form o-alkynylhalobenzenes has been well-established, [7,8] we were surprised to find that the amination of o-alkynylhalobenzenes for the synthesis of 2-substituted indoles was rarely studied. [10,11] We thus began our study to identify palladium catalyst systems that could efficiently catalyze the amination reaction of o-alkynylhalobenzenes.…”

“…With Pd(0)/P(t-Bu) 3 as the catalyst system, [14] several o-alkynylhaloarenes, which were prepared from 1-bromo-2-iodobenzene, 1-bromo-2-chlorobenzene and 1-chloro-2-iodobenzene by following reported methods, [7,8] were tested for the amination followed by the intramolecular hydroamination and our results are listed in Table 2. We found that 1-bromo-2-(2-phenylethynyl)-benzene and 1-chloro-2-(2-phenylethynyl)benzene reacted smoothly with both alkylamines and anilines to give 2-substitued indoles in excellent isolated yields (Table 2, entries 1 -6).…”