Reported is a modular one-step three-component synthesis of tetrahydroisoquinolines using a Catellani strategy. This process exploits aziridines as the alkylating reagents, through palladium/norbornene cooperative catalysis, to enable a Catellani/Heck/aza-Michael addition cascade. This mild, chemoselective, and scalable protocol has broad substrate scope (43 examples, up to 90 % yield). The most striking feature of this protocol is the excellent regioselectivity and diastereoselectivity observed for 2-alkyl- and 2-aryl-substituted aziridines to access 1,3-cis-substituted and 1,4-cis-substituted tetrahydroisoquinolines, respectively. Moreover, this is a versatile process with high step and atom economy.
By using commercially available 1,4-pentadiene
as a pronucleophile,
a copper(I)-catalyzed regioselective asymmetric allylation of ketones
is achieved. A variety of chiral tertiary alcohols bearing a terminal
(Z)-1,3-diene unit are generated in high (Z)/(E) ratio and high enantioselectivity.
Both aromatic ketones and aliphatic ketones serve as suitable substrates.
Furthermore, the reactions with (E)-C1(alkyl)-1,4-dienes proceed in moderate yields with acceptable enantioselectivity
but with low (Z,E)/others ratio,
which demonstrates the partial isomerization of (E)-allylcopper(I) species to (Z)-allylcopper(I) species
through 1,3-migration. Subsequent Heck reaction and olefin metathesis
compensate for the low efficiency with C1-1,4-dienes. The
synthetic utility of the product is further demonstrated by a copper(I)-catalyzed
regioselective borylation of the 1,3-diene group.
By using copper(I) homoenolates as nucleophiles, which are generated through the ring‐opening of 1‐substituted cyclopropane‐1‐ols, a catalytic asymmetric allylic substitution with allyl phosphates is achieved in high to excellent yields with high enantioselectivity. Both 1‐substituted cyclopropane‐1‐ols and allylic phosphates enjoy broad substrate scopes. Remarkably, various functional groups, such as ether, ester, tosylate, imide, alcohol, nitro, and carbamate are well tolerated. Moreover, the present method is nicely extended to the asymmetric construction of quaternary carbon centers. Some control experiments argue against a radical‐based reaction mechanism and a catalytic cycle based on a two‐electron process is proposed. Finally, the synthetic utilities of the product are showcased by means of the transformations of the terminal olefin group and the ketone group.
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