Catalyst-free facile and efficient one-pot synthesis of densely functionalized pyrroles and α-amino ketones

An efficient catalyst-free one-pot three-component synthesis of penta-substituted pyrroles has been successfully developed. A variety of penta-substituted pyrroles were straightforwardly synthesized from good to excellent yields (78%–93%) by using easily accessible starting materials under mild conditions. This protocol also provided α-amino ketones in good yields (87%–98%) without column chromatography.     

Highly efficient one-pot synthesis of fused pyrimidones from 2-heteroaryl amines and Morita–Baylis–Hillman carbonates via intermolecular cyclocondensation

A highly selective and efficient cyclocondensation reaction for construction of various 3-substituted-2H-pyrido[1,2-a]pyrimidin-2-ones and related fused pyrimidones from allylic carbonates and 2-heteroaryl amines has been developed. The transformation involves one-pot sequential aza-Michael addition, intramolecular acyl substitution, and [1,3]-H shift. The method is catalyst free, eco-friendly, scalable, and completes within a short reaction time, with no work-up, no column purification, and demonstrate a broad functional group tolerance.     

New flavonoid–porphyrin conjugates via Buchwald–Hartwig amination: synthesis and photophysical studies

New flavonoid–porphyrin conjugates were synthesized using the cross-coupling Buchwald–Hartwig amination for the coupling of flavonoid and porphyrin moieties. A unique di-substituted flavone–porphyrin conjugate was also synthesized under similar reaction conditions for the first time. All the conjugates were fully characterized by NMR spectroscopy. The photophysical properties namely fluorescence and singlet oxygen production were evaluated considering their use for photodynamic therapy applications.     

A simple and efficient stereoselective synthesis of (−)-cleistenolide

A simple and straightforward stereoselective synthesis of α,β-unsaturated δ-lactone, (?)-cleistenolide has been accomplished in 10 steps in an overall yield of 19%, starting from inexpensive and commercially available starting materials, respectively. This linear synthesis utilizes Sharpless asymmetric dihydroxylation, sulfur ylide mediated epoxide opening followed by ring-closing metathesis (RCM) for the formation of six-membered lactone ring as the key step sequence.     

Stereoselective synthesis of α,α-disubstituted amines by a sequential nucleophilic addition to O-protected cyanohydrins

The first enantioselective double nucleophilic addition reaction to O-protected cyanohydrin was achieved in 71% yield and 82:18 enantiomeric ratio by using a bis(BINOL)titanium Lewis acid complex. New (4S,5S)-2,2-dialkyl-4,5-bis(hydroxymethyl)-1,3-dioxolane titanium complexes were synthesized and they displayed good levels of enantioselection in the nucleophilic addition reaction.     

Selective carbophilic addition of organolithiums to thioamides. A novel synthesis of unsymmetrical ketones and α-alkylated amines

Thioamides, readily available from aldehydes, sulfur and secondary amines, can be converted to unsymmetrical ketones by the carbophilic addition of organolithiums to the thiocarbonyl group. Reduction of the intermediates with lithium aluminum hydride gives α-alkylated or α-arylated amines.     

Facile one-pot synthesis of tetrahydroisoquinolines from amino acids via hypochlorite-mediated decarboxylation and Pictet–Spengler condensation

A convenient method for oxidative decarboxylation of α-amino acids is presented. The aldehyde products may be isolated or converted to tetrahydroisoquinolines by addition of dopamine via Pictet–Spengler reaction. Racemic products are generated by phosphate buffer >300 mM to maximize regioselectivity. (S)-Enantiomer products are generated by norcoclaurine synthase reaction in maleic acid buffer to minimize chemical background reaction.     

A catalytic asymmetric ring-expansion reaction of isatins and α-alkyl-α-diazoesters: highly efficient synthesis of functionalized 2-quinolone derivatives

Asymmetric expansion: A catalytic asymmetric ring-expansion reaction of the title compounds occurs in the presence of a Sc(OTf)(3) catalyst bearing an N,N'-dioxide-based ligand. Highly functionalized 2-quinolone derivatives containing a chiral C4-quaternary stereocenter were obtained in high yields and high levels of selectivity under mild reaction conditions (see scheme; Tf=trifluoromethanesulfonyl).     

Efficient synthesis of α-alkylidene-β-lactams via NaOH-promoted intramolecular aza-Michael addition of α-carbamoyl ketene-S,S-acetals in aqueous media

A facile and efficient synthesis of substituted α-alkylidene-β-lactams have been developed via a NaOH-promoted intramolecular aza-Michael addition of α-carbamoyl, α-(1-chlorovinyl) ketene-S,S-acetals and subsequent nucleophilic vinylic substitution (S_NV) reaction in alcoholic aqueous media.     

A sulfonic acid functionalized ionic liquid as a homogeneous and recyclable catalyst for the one-pot synthesis of α-aminophosphonates

A sulfonic acid functionalized ionic liquid is used as a Brønsted acid catalyst for the one-pot, three-component synthesis of α-aminophosphonates from aldehydes and ketones at room temperature in water. This homogeneous catalytic procedure is simple and efficient and the catalyst can be reused at least six times without any noticeable decrease in catalytic activity.     

An efficient access to N-tert-butanesulfinyl aldimines in water: Application to one-pot synthesis of homoallylic amines, (+)-crispine A and (−)-coniine

An Efficient method for the syntheses of N-tert-butanesulfinyl aldimines in water was developed using Amberlyst-15 as catalyst. Subsequently, chiral homoallylic amines were synthesized in one pot from aldehydes by combining with In-promoted allylation in aqueous media. The total syntheses of (+)-Crispine A and (?)-Coniine were conducted to demonstrate the utility of this one-pot approach.     

A concise synthesis of paucifloral F and related indanone analogues via palladium-catalyzed α-arylation

A concise approach to synthesize paucifloral F was developed via a stereoselective palladium-catalyzed α-arylation reaction. The approach has also been applied in the synthesis of indanone analogues of Paucifloral F.     

Trichloroacetonitrile–hydrogen peroxide: a simple and efficient system for the selective oxidation of tertiary and secondary amines

A variety of tertiary and secondary amines were efficiently oxidized to their corresponding N-oxides and nitrones, respectively, using the trichloroacetonitrile–hydrogen peroxide system. The in situ generated trichloromethylperoxyimidic acid is the active reagent for the oxidation processes.     

A practical and efficient green synthesis of β-aminophosphoryl compounds via the aza-Michael reaction in water

Biphasic systems room temperature imidazolium ionic liquid (RTIL)/water or water as a solvent significantly accelerate the addition of amines to vinylphosphoryl compounds hence opening green and effective synthesis of β-aminophosphoryl compounds in excellent yields over short reaction times. The application of water, being the cheapest and most non-toxic solvent, without any catalyst or co-solvent, is more advantageous as it provides a simple isolation procedure for products having high purity (> 95% according to the NMR data) via simple freeze-drying and does not require extraction with organic solvents. The solubility of the starting phosphorus substrate in water does not play crucial role in the reaction as it was demonstrated using water insoluble diphenylvinylphosphine oxide. In contrast to typical procedures, using a reactant ratio (vinylphosphoryl compound: amine) of 2:1 readily resulted in double phosphorylation of primary amines, including polyamines, in water.     

Facile,efficient and diastereoselective synthesis of α-hydrazine tetrazoles through a novel one-pot four-component reaction

A novel and efficient method for the diastereoselective synthesis of α-hydrazine tetrazoles via an isocyanide-based multicomponent reaction is reported in good yields. The α-hydrazine tetrazoles were obtained by a facile azide Ugi four-component reaction (U-4CR) using cyclic ketones, trimethylsilyl azide, hydrazides, and corresponding isocyanide without any catalyst and with high bond forming efficiency at room temperature.     

A simple protocol for the synthesis of triazole-linked cyclic glycopeptidomimetics: a sequential Ugi-MCR and azide–alkyne cycloaddition approach

Sequential combination of Ugi-MCR and click chemistry has been employed for the synthesis of triazole linked cyclic glycopeptidomimetics. The protocol employs Poc-amino alkyl isonitriles, sugar-1-amines, azido acids, and simple aldehydes as precursors. The dual nature of the propargyloxycarbonyl (Poc) group was explored for amine protection as well as cycloaddition with an azide. All the cyclic glycopeptidomimetics are isolated and characterized.