A novel asymmetric [4+2] annulation of vinyl ketones with oxindole‐derived α,β‐unsaturated imines has been developed in the presence of a multifunctional thiourea‐phosphine catalyst derived from a natural amino acid, providing the first phosphine‐catalyzed enantioselective synthesis of 2′,3′‐dihydro‐1′H‐spiro[indoline‐3,4′‐pyridin]‐2‐ones in good yields with excellent stereoselectivities under mild conditions.
A synthetic strategy has been developed for the synthesis of 2‐dialkylaminoquinolines from easily available quinoline N‐oxides, tertiary amines, diisopropyl H‐phosphonate and carbon tetrachloride (CCl4) in one pot under metal‐free conditions at room temperature.
A concise synthesis of 1‐naphthols via cyclization of o‐iodoacetophenones and methyl ketones has been realized under very mild conditions. The cyclization process is initiated by a rare copper‐catalyzed arylation of simple methyl ketones with ortho‐iodoacetophenones.
An asymmetric tandem Michael addition–lactonization between ortho‐nitrovinylphenols and azalactones was investigated for constructing 3,4‐dihydrocoumarin backbones with a quaternary amino acid moiety. Under the catalysis of the chiral squaramide derived from L ‐tert‐leucine, a wide range of substituted (E)‐2‐(2‐nitrovinyl)phenols and azalactones were well tolerated in this tandem reaction to provide the corresponding biologically significant 3,4‐dihydrocoumarin derivatives in excellent yields with high levels of diastereo‐ and enantioselectivity.
A copper(I)‐catalysed domino transformation for the synthesis of tricyclic imidazobenzimidazole derivatives was developed. Using readily available primary propargylic amines and o‐haloarylcarbodiimides as the starting materials, a variety of substituted benzo[d]imidazo[1,2‐a]imidazoles was efficiently and selectively assembled. Further investigations indicated that the domino reaction was likely the result of a novel addition/cycloisomerisation/coupling process.
A novel and efficient domino process has been developed for the synthesis of 1,4‐benzoxazepine derivatives from a range of readily accessible N‐tosylaziridines, 2‐iodophenols and isocyanides. This process involves the aziridine ring‐opening reaction with 2‐iodophenol, followed by a palladium‐catalyzed isocyanide‐insertion reaction. This regioselective and high‐yielding transformation could be extended to its application for the synthesis of natural products and biologically interesting heterocycles.
By using N,N‐dimethylformamide (DMF) as a methylenating reagent, the copper‐catalyzed C H activation of indole was demonstrated as an efficient and facile protocol for synthesizing 3,3′‐diindolylmethane (DIM) and its derivatives. The results indicate that copper chloride was the best catalyst among the investigated transition metal salts, which affords an excellent regioselectivity and good yield when tert‐butyl hydroperoxide (TBHP) was used as an oxidant.
A catalytic enantioselective synthesis of α‐arylaminocyclobutanones from racemic α‐hydroxycyclobutanone and a selection of N‐alkylanilines has been established, via a tandem condensation/keto‐enol tautomerization process reminiscent of the Amadori and Heyns rearrangements.
A metal‐free C C bond formation method via the oxidative cross‐coupling reaction of isochroman and indole derivatives was established. Various α‐fuctionalized cyclic ethers were achieved in satisfactory yields using di‐tert‐butyl peroxide (DTBP) as the oxidant. This method is also a potentially efficient strategy for the construction of cyclic ether‐containing targets.
A new copper‐mediated synthesis of α‐sulfonylethanone oximes from styrenes, sodium arylsulfinates and tert‐butyl nitrite (t‐BuONO; TBN) is presented. This intermolecular three‐component method enables the one‐step formation of C N and C S bonds under mild conditions, and represents a new, straightforward approach to α‐sulfonylethanone oximes.
A highly efficient and enantioselective inverse electron‐demand hetero‐Diels–Alder reaction of in situ generated 1,2‐diaza‐1,3‐dienes with enol ethers has been developed with the use of a chiral copper/bisoxazoline complex as the catalyst. The reaction exhibits high enantioselectivity (up to 90% ee) and provides a robust and powerful method to synthesize a variety of structurally diverse and densely substituted chiral pyridazine derivatives in good to excellent yields.
The 8‐aminoquinoline‐directed, nickel(II)‐mediated ortho‐iodination of benzamides using molecular iodine has been developed. The process is highly regioselective and furnishes only monoiodinated products. A broad range of arenes and heteroarenes with diverse functional groups provided monoiodinated products in good to excellent yields.
A sequential one‐pot synthesis of Michael adducts of aroylmethylidenemalonates with activated aromatics is described. The method involves treatment of trans‐2‐aryl‐3‐nitro‐cyclopropane‐1,1‐dicarboxylates with boron trifluoride etherate to form aroylmethylidenemalonates in situ and then addition of activated aromatics such as indoles, carbazole, pyrrole, thiophenes, methoxybenzenes and benzodioxole followed by a catalytic amount of indium(III) triflate to the same reaction vessel. To prove the synthetic potential of the resulting Michael adducts, one of the adducts was transformed into a pharmaceutically interesting dihydropyridazinone derivative.
A highly enantioselective conjugate addition of arylboronic acids to cyclic as well as acyclic aromatic and aliphatic nitroalkenes is presented. The rhodium complexes obtained from deoxycholic acid‐derived binaphthyl and flexible biphenyl phosphites showed good activity as well as very high enantioselectivity (ee up to 99%) in the conjugated addition even in the presence of challenging substrates such as 1‐nitrocyclohexene or aliphatic acyclic nitroalkenes.
An N‐phthalimide‐protected (ortho‐aminophenyl)propiolate was prepared by the carboxylation of the corresponding silylalkyne precursor with carbon dioxide. The obtained propiolate was further transformed to various 3,4‐fused 2‐quinolones via cycloadditions and subsequent deprotection/lactam formation.
A sequential benzoin/Michael/acetalization tandem reaction catalyzed by NHC and amine together has been developed to assemble aromatic aldehydes and enals into chiral tetrahydrofuran derivatives bearing multiple functional groups and stereogenic centers with high stereoselectivity of up to 95:5 dr and 96% ee. The high yield and stereocontrol of this process may be due to both acid‐promoted symmetrization of racemic acyloins and iminium ion activation of enals.
