Palladium/Copper Co‐Catalyzed Cascade Metallo‐ene/Sonogashira Coupling Reaction of Allenamides

Abstract

A mild and efficient type of Pd/Cu-catalyzed allenamide allyl acetate reaction with terminal alkynes affording polyfunctionalized 2,3-dihydropyrrole derivatives is reported. Allenamide substrates went through two π-allyl palladium complex processes, and then it was trapped by terminal alkynes on the distal position via a Sonogashira reaction. Two new Csp 3 À Csp 2 and Csp 3 À Csp bonds were efficiently constructed in one pot.

Palladium‐Catalyzed Cascade Cyclization/Alkynylation Reactions

“…The group of Dong and Liu discovered a palladium/copper co‐catalyzed cascade metallo‐ene/Sonogashira coupling reaction of allenamides ( 50 ) with terminal alkynes, furnishing a series of structurally diverse 2,3‐dihydropyrroles 51 in moderate to good yields (Scheme ) . During this reaction process, two new C(sp 3 )−C(sp 2 ) and C(sp 3 )−C(sp) bonds were efficiently constructed.…”

“…The p complex Int-27 undergoes the nucleophilic attack of the allene moiety on the palladium centert og enerate ad ienylpalladium species Int-28.T hen, cis-insertion of the alkyne to inter- The group of Dong and Liu discovered ap alladium/copper co-catalyzed cascade metallo-ene/Sonogashira coupling reaction of allenamides (50)w ith terminal alkynes,f urnishing a series of structurally diverse 2,3-dihydropyrroles 51 in moderate to good yields (Scheme 27). [59] During this reactionp rocess, two new C(sp 3 )ÀC(sp 2 )a nd C(sp 3 )ÀC(sp) bonds were efficiently constructed. The reactionm echanism may involve the following steps:o xidative addition of allyl acetate (50)w ith Pd 0 generates palladium complex Int-31.M eanwhile, palladium intermediate Int-31 quickly transforms into p-allyl palladium species Int-32.T he following insertion into the allenamide form the C(sp 3 )ÀC(sp 2 )b ond gives the other p-allyl palladium inter-Scheme24.…”

Palladium and Copper Catalyzed Sonogashira cross Coupling an Excellent Methodology for C-C Bond Formation over 17 Years: A Review

“…The different ligands were used with palladium and copper catalysts. Both the electron donating and electron withdrawing substrates gave good yield [142]. It was also noted that isocoumarins are naturally occurring lactones and are biologically active.…”

“…The different ligands were used with palladium and copper catalysts. Both the electron donating and electron withdrawing substrates gave good yield [142].…”

Pd‐Catalyzed Cascade Metallo‐Ene Cyclization/Metallo‐Carbene Coupling of Allenamides

“…As shown in Scheme 1, in the presence of palladium(0) species, the allenamides A could generate two π‐allyl palladium intermediates B and B’ with C sp 3 −C sp 2 bond formation via Metallo‐ene transformation. Based on intermediates B and B’ , we have applied Suzuki coupling and Sonogashira coupling to capture the intermediates to construct 2,3‐2H‐pyrrole derivates ( I ) and ( II ) bearing aromatic or alkynyl groups [13b–c] . To further explore, novel methodologies to construct functionalized pyrroles, we continued to consider the transformation of intermediate B and B’ .…”