Palladium-catalyzed enantioselective arylation of trichloro- or tri-/difluoroacetaldimine precursors

A palladium-catalyzed asymmetric α-arylation of N-carbamoyl imine precursors containing CCl3, CF3 and CF2H is presented. This protocol provides facile access to a series of chiral α-aryl trichloroethylamines bearing various functional groups, with moderate to high yields (40-82% yield) and high enantioselectivity (80-99% ee).

Copper-catalyzed trichloromethylative carbonylation of ethylene

Difunctionalization of alkenes is an efficient strategy for the synthesis of complex compounds from readily available starting materials. Herein, we developed a copper-catalyzed visible-light-mediated trichloromethylative carbonylation of ethylene by employing commercially available CCl4 and CO as trichloromethyl and carbonyl sources, respectively. With this protocol, various nucleophiles including amines, phenols, and alcohols can be rapidly transformed into β-trichloromethyl carboxylic acid derivatives with good functional-group tolerance. Bis-vinylated γ-trichloromethyl amides can also be obtained by adjusting the pressure of carbon monoxide and ethylene. In addition, this photocatalytic system can be successfully applied in the late-stage functionalization of bioactive molecules and pharmaceutical derivatives as well.

α-Amino Radical-Mediated Difunctionalization of Alkenes with Polyhaloalkanes and N-Heteroarenes

Herein, we report a mild and practical protocol for the α-perchloroalkyl β-heteroarylation of alkenes using available chloroform as the dichloromethyl source via α-amino radical-mediated halogen-atom transfer. Various substrates are compatible under mild reaction conditions, providing the corresponding products in moderate to good yields. This strategy gives an efficient and convenient method for the introduction of chloroalkyl motifs into N-heteroarenes. The control experiment demonstrates that the α-amino radical generated in situ is a key intermediate in the transformation.

Transient self-assembly of metal-organic complexes

Implementing transient processes in networks of dynamic molecules holds great promise for developing new functional behaviours. Here we report that trichloroacetic acid can be used to temporarily rearrange networks of dynamic imine-based metal complexes towards new equilibrium states, forcing them to express complexes otherwise unfavourable in their initial equilibrium states. Basic design principles were determined for the creation of such networks. Where a complex distribution of products was obtained in the initial equilibrium state of the system, the transient rearrangement temporarily yielded a simplified output, forcing a more structured distribution of products. Where a single complex was obtained in the initial equilibrium state of the system, the transient rearrangement temporarily modified the properties of this complex. By doing so, the mechanical properties of an helical macrocyclic complex could be temporarily altered by rearranging it into a [2]catenane.

The polychloromethylation/acyloxylation of 1,6-enynes with chloroalkanes and diacyl peroxides through dual-role designs

The novel polychloromethylation/acyloxylation of 1,6-enynes with chloroalkanes and diacyl peroxides through dual-role designs has been developed to prepare 2-pyrrolidinone derivatives with polychloromethyl units with the use of an inexpensive copper salt under mild conditions. This strategy includes two dual-role designs, not only improving atomic utilization but also allowing a cleaner process. The wide substrate scope and simple reaction conditions demonstrate the practicability of this protocol.

Synthesis of β-Polychlorinated Alkynes Enabled by Copper-Catalyzed Multicomponent Reaction

Functional molecules bearing polychlorinated moieties usually play versatile roles in organic synthesis and biochemistry. A copper-catalyzed multicomponent polychloro-carboalkynylation of alkenes presents an efficient and operationally simple approach for the synthesis of β-polychlorinated alkynes. Mechanistic experiments were conducted demonstrating that an in situ generated copper acetylide complex was the real catalyst and reactive intermediate during the copper-catalytic cycle. And enantioselective exploration demonstrated potential application for the synthesis of chiral β-polychlorinated alkynes.

Free Radical Cascade Carbochloromethylations of Activated Alkenes

Free radical carbochloromethylations of ortho-cyanoarylacrylamides and N-(arylsulfonyl)acrylamides have been developed by employing simple alkyl chlorides as the chloromethyl source. The transformations are characterized by wide functional group compatibility and utilizing readily available reagents, thus providing efficient methods for constructing polychloromethyl-substituted quinoline-2,4-diones and α-aryl-β-polychloromethylated amides.

Radical Relay Trichloromethylacylation of Alkenes through N-Heterocyclic Carbene Catalysis

N-Heterocyclic carbene catalysis enabling vicinal trichloromethylacylation of alkenes using tetrachloromethane and aldehydes has been developed. The reaction involves single electron transfer from the enolate form of the Breslow intermediate to tetrachloromethane to generate the persistent Breslow intermediate-derived ketyl radical and a transient trichloromethyl radical. After radical addition of the trichloromethyl radical to an alkene, the prolonged alkyl radical is preferentially captured by the ketyl radical over tetrachloromethane leading to the atom transfer radical addition product.

Catalytic Asymmetric Mannich Type Reaction with Tri-/Difluoro- or Trichloroacetaldimine Precursors

A highly efficient catalytic asymmetric Mannich type reaction of CF₃-_, CF₂H-, or CCl₃-acetaldimine precursors by a chiral primary amine is presented. This protocol provides facile access to chiral CF₃-, CF₂H-, or trichloroethyl amines in excellent yields and high enantioselectivity (up to 99% yield, up to >99% ee).

Organocatalyzed Decarboxylative Trichloromethylation of Morita-Baylis-Hillman Adducts in Batch and Continuous Flow

Two protocols for the organocatalyzed decarboxylative trichloromethylation of Morita-Baylis-Hillman (MBH) substrates have been developed. Applying sodium trichloroacetate, as the trichloromethyl anion precursor, in combination with an organocatalyst and acetylated MBH-alcohols, the desired trichloromethylated products were obtained in good yields at room temperature in batch. The method was next extrapolated into a two-step continuous flow protocol, starting directly from the MBH alcohols, in combination with tributylamine acting both as base and catalyst. The flow process proved superior to the batch approach, reducing the reaction time from 16 hours to only 20 minutes, with increased yields for all investigated entries. Two examples were also taken to scale-up in flow producing more than 10 grams of both trichloromethylated targets. Finally, substitution of the organocatalyst to (DHQ)₂ PHAL or (DHQD)₂ PHAL induced chiral transfer to the generated stereocenter in the reaction attaining selectivities with nearly 90 % ee.

Three-component carboarylation of unactivated imines with arynes and carbon nucleophiles

With 2-(trimethylsilyl)aryl triflates as aryne precursors, the title reaction proceeds smoothly to afford functionalized tertiary amines under transition metal-free conditions.

Catalyst free decarboxylative trichloromethylation of aldimines

A catalyst free decarboxylative trichloromethylation of imines to afford different trichloromethyl sulfonyl and sulfinyl amines has been presented.

Diastereoselective Addition of Metal α-Fluoroenolates of Carboxylate Esters to N-tert-Butylsulfinyl Imines: Synthesis of α-Fluoro-β-amino Acids

We report a diastereoselective addition reaction of fluoroacetate and α-alkylated fluoroacetate to N-tert-butylsulfinyl imines. This method provides a concise route to α-fluoro-β-amino acids containing fluorinated quaternary stereogenic carbon centers with very good yields and high diastereoselectivities. This protocol has the benefit of using abundant and readily accessible starting materials and is operationally simple. Additionally, the stereochemical outcome of the present reaction was different from that of the previously known addition of comparable nonfluorinated, brominated, and chlorinated enolates to N-sulfinyl imines, suggesting that an open transition state (rather than a closed one) is involved in the current fluoroalkylation reaction.

Decarboxylative Reissert type trifluoro- and trichloro-methylation of (iso)quinoline derivatives in batch and continuous flow

Copper-free decarboxylative trifluoro- and trichloromethylation of isoquinoline and quinoline derivatives through Reissert type reactions in batch and telescoped continuous flow.

Reaction of cyclopropenes with a trichloromethyl radical: unprecedented ring-opening reaction of cyclopropanes with migration

The triethylborane-mediated direct addition of chloroform to cyclopropenes afforded trichloromethylcyclopropanes. In contrast, the use of dimethylzinc gave the unconjugated diene via ring-opening reactions.

Synthesis of α-tribromomethylamines via Mg-mediated addition of bromoform to imines

Mg-mediated addition of bromoform to electron deficient imines such as N-sulfonylimines affords α-tribromomethylated N-sulfonylamines in good to excellent yields. The procedure could be further simplified by transforming the imine precursors, α-sulfonyl-N-tosyl- and Boc-amines, in one pot to the corresponding α-tribromomethyl derivatives. Facile removal of the Boc protecting group in nearly quantitative yield and a silver carbonate mediated monodebromination have also been demonstrated.

Synthesis of cis-C-iodo-N-tosyl-aziridines using diiodomethyllithium: reaction optimization, product scope and stability, and a protocol for selection of stationary phase for chromatography

The preparation of C-iodo-N-Ts-aziridines with excellent cis-diastereoselectivity has been achieved in high yields by the addition of diiodomethyllithium to N-tosylimines and N-tosylimine-HSO2Tol adducts. This addition-cyclization protocol successfully provided a wide range of cis-iodoaziridines, including the first examples of alkyl-substituted iodoaziridines, with the reaction tolerating both aryl imines and alkyl imines. An ortho-chlorophenyl imine afforded a β-amino gem-diiodide under the optimized reaction conditions due to a postulated coordinated intermediate preventing cyclization. An effective protocol to assess the stability of the sensitive iodoaziridine functional group to chromatography was also developed. As a result of the judicious choice of stationary phase, the iodoaziridines could be purified by column chromatography; the use of deactivated basic alumina (activity IV) afforded high yield and purity. Rearrangements of electron-rich aryl-iodoaziridines have been promoted, selectively affording either novel α-iodo-N-Ts-imines or α-iodo-aldehydes in high yield.