Allylic C–H Alkynylation via Copper-Photocatalyzed Cross-Dehydrogenative Coupling

Abstract

An efficient, novel photocatalyzed allylic-alkynylation methodology via copper-based cross-dehydrogenative coupling (CDC) is described. Different types of 1,4-enyne compounds were synthesized in one step at room temperature using copper(I) terpyridyl complex as photocatalyst/initiator. This procedure is an improvement and to some extent complementary to previously reported thermal CDC methods. Preliminary investigations on the reaction mechanism are also presented.

Regioselective and Redox‐Neutral Cp*IrIII‐Catalyzed Allylic C−H Alkynylation

“…However, the majority of reports focuses on the Tsuji–Trost type alkynylation of prefunctionalized olefins under Pd [10c] or Ir [10d] catalysis. Alternative strategies include Cu, [10f] Ni, [10a,b] Fe, [10e,g] or photoredox catalysis [10h] . However, most of these important reports are either again confined to the use of prefunctionalized allylic substrates, or only allow the alkynylation of cyclic or activated olefins.…”

Cross‐Dehydrogenative Alkynylation: A Powerful Tool for the Synthesis of Internal Alkynes

“…This reaction is the first example of the alkynylation of benzylic C−H bonds that are not adjacent to a nitrogen atom. Through a radical strategy, the α‐C−H alkynylation of ethers, allylic compounds and 4‐thiazolidinone with aromatic terminal alkynes was also realized with a copper catalyst recently.…”

Regioselektive und redox‐neutrale Cp*IrIII‐katalysierte allylische C‐H‐Alkinylierung

“…Die Mehrzahl der Berichte konzentriert sich jedoch auf die Tsuji‐Trost‐artige Alkinylierung von präfunktionalisierten Olefinen unter Pd‐ [10c] oder Ir‐ [10d] Katalyse. Alternative Strategien beinhalten Cu‐, [10f] Ni‐, [10a,b] Fe‐ [10e,g] oder Photoredox‐Katalyse [10h] . Die meisten dieser wichtigen Berichte sind jedoch entweder erneut auf die Verwendung vorfunktionalisierter allylischer Substrate beschränkt oder erlauben nur die Alkinylierung von zyklischen oder aktivierten Olefinen.…”