Xufeng Lin

The enantioselective catalytic construction of structurally sophisticated helicenes integrating both helical and central chirality remains a formidable challenge, and organocatalytic strategies for helicene synthesis are still severely underexplored compared with transition-metal catalysis. Benefiting from the inherent stereocontrolling ability of chiral phosphoric acid (CPA), we herein report a facile, metal-free asymmetric [3+3] annulation strategy for efficient synthesis of chromene-based helicenes with dual central and helical chirality. The reaction employs readily available benzo[c]carbazol-2-ols (easily prepared via one-step Bucherer-type synthesis) and propargylic alcohols as substrates. A dual hydrogen-bonding activation mode between the substrate and CPA catalyst guarantees good diastereo- and enantioselectivities, delivering complex chiral azachromenohelicenes in high yields. The obtained enantioenriched helicenes possess high configurational stability and strong circular dichroism responses. This work provides a scalable organocatalytic platform for constructing multifunctional chiral helicene scaffolds, offering promising candidates for advanced chiroptical functional materials.

A hexacationic cage incorporating three urea units can encapsulate two mutually repulsive anions in close proximity through a combination of hydrogen bonding and electrostatic interactions. This leads to exceptionally high binding affinities, with a K ₁ × K ₂ value of approximately 10 ²⁰ M ^‒2 in MeCN‐ d ₃ , for pairs of Cl ^‒ or F ^‒ anions. In its unbound state, the cage adopts a collapsed conformation stabilized by intramolecular interactions. These interactions are disrupted upon binding of the first anion guest, inducing an unfolded conformation that facilitates the binding of the second guest. Consequently, despite repulsion, the second Cl ^‒ anion binds more strongly than the first by three orders of magnitude. This work presents a straightforward strategy for mimicking biological allosteric regulation and offers insights into the underlying physicochemical principles. The strong halide binding enables several applications. The cage can extract F ^‒ from CaF ₂ , suggesting a route to utilize fluorine from fluorspar for fluorochemical synthesis that bypasses the generation of hazardous HF. Furthermore, the cage can extract Cl ^‒ or Br ^‒ anions from organic halides, thereby stabilizing the corresponding carbocations and accelerating reactions involving these intermediates. In addition, the high affinity of the cage for halide anions released from fire suppressants provides for corrosion resistance.

A hexacationic cage incorporating three urea units can encapsulate two mutually repulsive anions in close proximity through a combination of hydrogen bonding and electrostatic interactions. This leads to exceptionally high binding affinities, with a K ₁ × K ₂ value of approximately 10 ²⁰ M ^‒2 in MeCN‐ d ₃ , for pairs of Cl ^‒ or F ^‒ anions. In its unbound state, the cage adopts a collapsed conformation stabilized by intramolecular interactions. These interactions are disrupted upon binding of the first anion guest, inducing an unfolded conformation that facilitates the binding of the second guest. Consequently, despite repulsion, the second Cl ^‒ anion binds more strongly than the first by three orders of magnitude. This work presents a straightforward strategy for mimicking biological allosteric regulation and offers insights into the underlying physicochemical principles. The strong halide binding enables several applications. The cage can extract F ^‒ from CaF ₂ , suggesting a route to utilize fluorine from fluorspar for fluorochemical synthesis that bypasses the generation of hazardous HF. Furthermore, the cage can extract Cl ^‒ or Br ^‒ anions from organic halides, thereby stabilizing the corresponding carbocations and accelerating reactions involving these intermediates. In addition, the high affinity of the cage for halide anions released from fire suppressants provides for corrosion resistance.

A chiral carboxylic acid‐assisted, rhodium‐catalyzed asymmetric CH activation of sulfoximines with iodonium ylides has been developed. A broad range of sulfur‐stereogenic sulfoximines were obtained in yields of up to 95% and with enantioselectivities of up to 97:3 er. Notably, iodonium ylides generated in situ from 1,3‐diketones and hypervalent iodine reagents were also compatible with this asymmetric reaction. The synthetic utility and practicality of this method were further demonstrated by oxidation of one product with m ‐CPBA providing the ten‐membered cyclic chiral sulfoximine. Mechanistic investigations were conducted by H/D exchange, kinetic isotope effect, intermolecular competition, and control experiments.

A novel organophotoredox‐catalyzed [3 + 2] cycloaddition strategy for the synthesis of spirocyclopentane oxindoles is reported, employing N ‐aryl cyclopropylamines and isatin‐derived alkenes as readily available coupling partners. This protocol affords diverse spirocyclopentane oxindole derivatives in excellent yields (up to 94%) and good diastereoselectivities (up to 96:4 dr) under mild conditions. The transformation is facilitated by a dual catalytic system consisting of Eosin Y as photoredox catalyst and diphenyl phosphate (PA) as organocatalyst, with N , N ‐diisopropylethylamine (DIPEA) as a crucial additive.

Planar chiral bisphosphine ligands based on diphenyl [2.2]paracyclophane (PhPhanePHOS) were successfully synthesized in a practical manner in four steps from commercially available 4,12-bisbromo-[2.2]paracyclophane as a new family of bisphosphine ligands. The novel PhPhanePHOS ligands provide high catalytic activity in Pd-catalyzed asymmetric allylic alkylation reactions in preliminary experiments.

The development of privileged chiral carboxylic acids is crucial for enabling asymmetric C-H activation catalyzed by achiral high-valent d6 transition metals. We report the synthesis of a new chiral carboxylic acid that enables Ir(III)-catalyzed asymmetric C-H activation/desymmetrization of sulfoximines with α-bromo ketones. A diverse range of sulfur-stereogenic sulfoximines were synthesized with high yields (up to 90%) and excellent enantioselectivity (up to 97:3 er). The reaction maintained its efficiency upon scale-up, and one of the products 6aa could be readily transformed into the five-membered chiral cyclic sulfoximine derivative. Detailed mechanistic studies establish C-H bond cleavage as the rate-determining step. Furthermore, the alkylated reaction intermediate was successfully isolated and demonstrated complete retention of enantioselectivity upon conversion to the corresponding product.

Unnatural α-amino acids (α-UAAs) are essential components in the development of biologically active compounds, pharmaceuticals, ligands, and catalysts.

A highly enantioselective Friedel–Crafts reaction between C2-unsubstituted naphthyl-indoles and racemic 3-methylated-3H-pyrrolides catalyzed by chiral phosphoric acids has been developed. This reaction provides an efficient and facile route to a series of heterotricyclic triarylmethanes containing axially chiral naphthyl-indole and centrally chiral pyrrole moieties under mild conditions. Moreover, biological evaluation discovered one of these products with promising antitumor activity, and demonstrates its potential application in medicinal chemistry.