Alkine als alternativer Einstieg in elektrophile und nukleophile Übergangsmetall‐katalysierte Allylierungen

Abstract

Eine Reihe von Übergangsmetall‐Katalysatoren ist in der Lage, terminale und interne Alkine intermediär in entsprechende Allylmetall‐Verbindungen zu überführen, die ihrerseits elektrophile oder nukleophile Reaktivitäten aufweisen können. Während klassische Methoden zur Herstellung von Allylmetall‐Spezies oftmals von der Bildung stöchiometrischer Mengen an Nebenprodukten begleitet sind, ermöglicht der Einsatz von Alkinen als Allylmetall‐Vorstufen vollständig atomökonomische katalytische Prozesse, die außerdem mit hohen Enantioselektivitäten ablaufen.

Regiodivergent Hydroaminoalkylation of Alkynes and Allenes by a Combined Rhodium and Photoredox Catalytic System

“…[1] From the perspective of atom economy and synthetic efficiency, [2] our group developed af acile and efficient access to branched allylic products thrugh rhodium catalyzed regio-and stereoselective coupling reactions of alkynes and allenes with diverse N, O, S, and Cp ronucleophiles. [3] In contrast to the traditional transition-metal-catalyzed allylic substitution reaction and allylic C À Ho xidation, this protocol does not require preinstalled leaving groups or stoichiometric amounts of oxidants, which greatly enhance their attractiveness in modern chemical synthesis. [4] Although in recent years great efforts have been devoted to explore the breadth of nucleophilic partners by our group and others,c arbon prenucleophiles have primarily been limited to enolizable carbonyl compounds or electron-rich arenes.…”

Asymmetric hydroalkylation of alkynes and allenes with imidazolidinone derivatives: α-alkenylation of α-amino acids

“… 8 Recently, an intramolecular method for the α-alkenylation of α-AA was reported using diastereoselective rearrangement of an N ′-alkenyl urea substrate 9 according to the Seebach's “self-regeneration of stereocenters” method ( Scheme 1a ). 10 Thus, considering our extended knowledge on the regioselective addition of different pronucleophiles to allenes and alkynes, 11 we envisioned that the direct intermolecular hydroalkylation of alkynes and allenes with imidazolidinone derivatives may provide a new way to obtain quaternary α-alkenyl substituted amino acids ( Scheme 1b ). This new transformation is highlighted by an increase in the structural complexity of amino acids through the formation of a new C–C bond which generates a new quaternary stereocenter in high diastereoselectivity.…”