Rh(I)-Catalyzed Direct ortho-Alkenylation of Aromatic Ketimines with Alkynes and Its Application to the Synthesis of Isoquinoline Derivatives

Abstract

[reaction: see text] Novel synthetic methods of both ortho-alkenylated aromatic ketones and isoquinoline derivatives have been developed through the Rh(I)-catalyzed direct ortho-alkenylation of common aromatic ketimines with alkynes. Furthermore, a highly efficient one-pot synthesis of isoquinoline derivatives was achieved by simply mixing aromatic ketone, benzylamine, and alkyne under a Rh(I) catalyst.

C–H Bond Alkenylation

“…Benzene and furans react with diphenylacetylene in the presence of Rh 4 (CO) 12 catalyst at 220 • C under CO (25 kg cm −2 ) to produce trisubstituted ethenes (Scheme 18.74). By using RhCl(PPh 3 ) 3 as a catalyst, 2-phenylpyridines and aromatic imines also react with alkynes to afford the corresponding alkenylated products, as were shown by Lim and Kang [76] and by Jun [77], respectively (Scheme 18.76 and Scheme 18.77). The latter products can be converted to isoquinoline derivatives on treatment with an amine.…”

Rh‐Catalyzed Synthesis of Nitrogen‐Containing Heterocycles

“…Jun et al demonstrated a Rh(I)-catalyzed cyclization of an N-benzyl aromatic ketimine with diphenylacetylene to provide isoquinoline 44 [27]. The chelationassisted C-H activation strategy was employed for the first time for isoquinoline synthesis.…”

Catalytic Addition of C – H Bonds to C – C Multiple Bonds

“…29) [73]. Rhodium(I) complexes also functioned as a catalyst for the alkenylation of C -H bonds in arylpyridines and aromatic imines [84,85]. The corresponding ortho alkenylation products were obtained in high yields (Eq.…”

“…Terminal acetylenes are applicable in the case of the RhCl(PPh 3 ) 3 -catalyzed alkenylation of ketimines (Eq. 31) [85].…”

“…32). The reaction pathway is not clarified, but two molecules of the alkenylation product participated in the unusual tandem coupling reaction involving C -H bond cleavage and electrophilic reactions [85].…”