Enantioselective synthesis of bicyclo[3.n.1]alkanes by chiral phosphoric acid-catalyzed desymmetrizing Michael cyclizations

Organocatalyzed enantio- and diastereoselective isomerization of prochiral 1,3-cyclohexanediones into nonalactones bearing distant stereocenters

The lactonization of 2-(2-nitrophenyl)-1,3-cyclohexanediones containing an alcohol side chain and up to three distant prochiral elements is reported by isomerization under the mediation of simple organocatalysts such as quinidine. Through a process of ring expansion, strained nonalactones and decalactone are produced with up to three stereocenters in high er and dr (up to 99 : 1). Distant groups, including alkyl, aryl, carboxylate and carboxamide moieties, were examined.

Copper-Catalyzed Asymmetric Synthesis of Bicyclo[3.n.1]alkenones

A series of highly strained bicyclo[3.n.1]alkenones have been successfully constructed in good-to-excellent enantioselectivities and moderate-to-good yields via copper-catalyzed formal [3+3] cycloaddition. The versatile chiral cycloadducts could be selectively converted into various valuable bridge systems, which hold considerable potential for the construction of natural and bioactive compounds containing a [3.n.1] moiety.

Constructing chiral bicyclo[3.2.1]octanes via palladium-catalyzed asymmetric tandem Heck/carbonylation desymmetrization of cyclopentenes

Transition-metal-catalyzed tandem Heck/carbonylation reaction has emerged as a powerful tool for the synthesis of structurally diverse carbonyl molecules, as well as natural products and pharmaceuticals. However, the asymmetric version was rarely reported, and remains a challenging topic. Herein, we describe a palladium-catalyzed asymmetric tandem Heck/carbonylation desymmetrization of cyclopentenes. Alcohols, phenols and amines are employed as versatile coupling reagents for the construction of multifunctional chiral bicyclo[3.2.1]octanes with one all-carbon quaternary and two tertiary carbon stereogenic centers in high diastereo- and enantioselectivities. This study represents an important progress in both the asymmetric tandem Heck/carbonylation reactions and enantioselective difunctionalization of internal alkenes.

A sustainable catalytic enantioselective synthesis of norstatine derivatives

Norstatine derivatives are of important value in pharmaceutical science. However, their catalytic asymmetric synthesis is rare. We developed a sustainable method via chiral phosphoric acid (CPA)-[Rh(OAc)₂]₂ co-catalyzed multi-component reactions (MCR) of diazoacetates with alcohol/water and imines. This method allows us to synthesize a library of 45 norstatines with excellent enanotioselectivites and broad substrate scope which includes anti-α-aryl-norstatines 11-1, anti-α-alkyl-norstatines 11-2, syn-α-hydro-norstatines 11-3 and syn-α-aryl-norstatines 11-4. The sustainability of this method lies in the reliable scalability, improved safety, and reusable [Rh(OAc)₂]₂ catalyst. The synthetic value of norstatine derivatives was demonstrated by preparing oxazolinone 14, ezetimibe analogue 15, and Taxol C-13 chain 16. Mechanistic study reveals that the synergetic catalysis of CPA and [Rh(OAc)₂]₂ is essential to maintain chemo- and enantioselectivity. Control experiments support the mechanism where the reactions proceed through the trapping of hyper-reactive oxonium ylides with imines. Shortly, we report herein the sustainable catalytic enantioselective synthesis of both syn- and anti-norstatine derivatives. We believe that this method might shed light on the sustainable synthesis of norstatine derivative-based drug candidates.

Palladium-Catalyzed Asymmetric Intramolecular Reductive Heck Desymmetrization of Cyclopentenes: Access to Chiral Bicyclo[3.2.1]octanes

A palladium-catalyzed asymmetric reductive Heck reaction of unactivated aliphatic alkenes, with eliminable β-hydrogen atoms, has been realized for the first time. A series of optically active bicyclo[3.2.1]octanes bearing chiral quaternary and tertiary carbon stereocenters were obtained in good yields with excellent enantioselectivities, exhibiting good functional-group tolerance and scalability. Moreover, deuterated optically active bicyclo[3.2.1]octanes were also obtained in high efficiency.

Asymmetric addition of α-branched cyclic ketones to allenamides catalyzed by a chiral phosphoric acid

Asymmetric addition of unactivated α-branched cyclic ketones to allenamides catalyzed by a chiral phosphoric acid catalyst, generates an all-carbon quaternary stereocenter with broad substrate scope and high enantioselectivity.

We describe the asymmetric addition of unactivated α-branched cyclic ketones to allenamides catalyzed by a chiral phosphoric acid, generating an all-carbon quaternary stereocenter with broad substrate scope and high enantioselectivity. The products are easily transformed into their corresponding 1,5- and 1,4-ketoaldehyde derivatives, which are both important building blocks in organic synthesis.

Dinuclear zinc-catalyzed desymmetric intramolecular aldolization: an enantioselective construction of spiro[cyclohexanone-oxindole] derivatives

A bis-ProPhenol zinc complex-catalyzed asymmetric desymmetrizing intramolecular aldol or aldol condensation reaction is reported, which furnishes spiro[cyclohexanone-oxindole] derivatives in good yields with moderate to high enantioselectivities.

A switchable dual organocatalytic system and the enantioselective total synthesis of the quadrane sesquiterpene suberosanone

Switch it! The combination of aminocatalysis and N-heterocyclic carbene catalysis has been extended to a switchable dual catalytic system.

Catalytic Asymmetric Reactions of 4-Substituted Indoles with Nitroethene: A Direct Entry to Ergot Alkaloid Structures

A domino Friedel-Crafts/nitro-Michael reaction between 4-substituted indoles and nitroethene is presented. The reaction is catalyzed by BINOL-derived phosphoric acid catalysts, and delivers the corresponding 3,4-ring-fused indoles with very good results in terms of yields and diastereo- and enantioselectivities. The tricyclic benzo[cd]indole products bear a nitro group at the right position to serve as precursors of ergot alkaloids, as demonstrated by the formal synthesis of 6,7-secoagroclavine from one of the adducts. DFT calculations suggest that the outcome of the reaction stems from the preferential evolution of a key nitronic acid intermediate through a nucleophilic addition pathway, rather than to the expected "quenching" through protonation.

Nonenzymatic enantioselective synthesis of all-carbon quaternary centers through desymmetrization

The asymmetric desymmetrization of meso or prochiral compounds containing an all-carbon quaternary center is an attractive alternative to classical synthetic approaches aimed at the asymmetric formation of a new C-C bond. This review focuses on nonenzymatic desymmetrizations that utilize transition metal catalysts or organocatalysts to distinguish between enantiotopic groups to generate enantioenriched compounds containing all-carbon quaternary stereocenters.

Base catalyzed synthesis of bicyclo[3.2.1]octane scaffolds

A base-catalyzed and time controlled reaction of 1,3-cyclopentanediones tethered to activated olefins afforded in high yields either bicyclo[3.2.1]octane-6,8-dione or bicyclo[3.2.1]octane-6-carboxylate derivatives.

Synthesis of highly strained bicyclic[3.n.1]alkenes by a metal-catalyzed Conia-ene reaction

A high yielding metal-catalysed Conia-ene reaction of 2-acetylenic ketones for the synthesis of bicyclo[3.n.1]alkenes has been developed.