Nano-tube TiO_2 as a new catalyst for eco-friendly synthesis of imines in sunlight

Nanomaterials are considered as suitable heterogeneous catalysts for many organic reactions.Herein nano-tube TiO₂ has been reported as a heterogeneous catalyst,for synthesis of imines in sunlight at room temperature under solvent-free conditions.The condensation of less electrophilic carbonyl compounds with poorly nucleophilic amines was afforded imines in excellent yields.     

Novel 2-pyridone synthesis via nucleophilic addition of malonic esters to alkynyl imines

[reaction: see text] A novel 2-pyridone synthesis via nucleophilic addition of malonic esters to alkynyl imines has been developed. The reaction of dialkylalkyl sodiomalonates with alkynyl imines provided 2-pyridones in good to excellent yields.     

Understanding the Origins of Nucleophilic Hydride Reactivity of a Sodium Hydride–Iodide Composite

Sodium hydride (NaH) has been commonly used as a Brønsted base in chemical syntheses, while it has rarely been employed to add hydride (H^?) to unsaturated electrophiles. We previously developed a procedure to activate NaH through the addition of a soluble iodide source and found that the new NaH–NaI composite can effect even stereoselective nucleophilic hydride reductions of nitriles, imines, and carbonyl compounds. In this work, we report that mixing NaH with NaI or LiI in tetrahydrofuran (THF) as a solvent provides a new inorganic composite, which consists of NaI interspersed with activated NaH, as revealed by powder X‐ray diffraction, and both solid‐state NMR and X‐ray photoelectron spectroscopies. DFT calculations imply that this remarkably simple inorganic composite, which is comprised of NaH and NaI, gains nucleophilic hydridic character similar to covalent hydrides, resulting in unprecedented and unique hydride donor chemical reactivity.     

Stereoselective synthesis of N-heterocycles: application of the asymmetric Cu-catalyzed addition of Et2Zn to functionalized alkyl and aryl imines

The preparation of N-heterocycles from alkyl- and aryl-substituted imines is described. The key step involves a copper-catalyzed addition of diethylzinc to functionalized alkyl-substituted imines that were generated in situ from the sulfinic acid adducts. The nucleophilic addition products were then converted to 2-substituted pyrrolidines and piperidines. Aryl-substituted imines were transformed into enantioenriched 1- and 1,4-substituted tetrahydroisoquinolines.     

Magnesium perchlorate as an efficient catalyst for the synthesis of imines and phenylhydrazones

Magnesium perchlorate has been found to be an efficient catalyst for the synthesis of imines and phenylhydrazones by the reaction of carbonyl compounds with amines and phenylhydrazine in high yields at room temperatures and in short times. The condensation of less electrophilic carbonyl compounds with poorly nucleophilic amines affords the imines in excellent yields.     

Nucleophilic perfluoroalkylation of aldehydes, ketones, imines, disulfides, and diselenides

Using a procedure analogous to that developed for nucleophilic trifluoromethylation, the perfluoroalkyl anion reagents created by mixing C2F5I and n-C4F9I with tetrakis(dimethylamino)ethylene (TDAE) were effective in their nucleophilic reactions with aldehydes, ketones, imines, disulfides, and diselenides. Irradiation proved beneficial in the aldehyde and ketone reactions.     

Unprecedented Nucleophilic Additions of Highly Polar Organometallic Compounds to Imines and Nitriles Using Water as a Non‐Innocent Reaction Medium

In contrast to classic methods carried out under inert atmospheres with dry volatile organic solvents and often low temperatures, the addition of highly polar organometallic compounds to non‐activated imines and nitriles proceeds quickly, efficiently, and chemoselectively with a broad range of substrates at room temperature and under air with water as the only reaction medium. Secondary amines and tertiary carbinamines are furnished in yields of up to and over 99 %. The significant solvent D/H isotope effect observed for the on‐water nucleophilic additions of organolithium compounds to imines suggests that the on‐water catalysis arises from proton transfer across the organic–water interface. The strong intermolecular hydrogen bonds between water molecules may play a key role in disfavoring protonolysis, which occurs extensively in other protic media such as methanol. This work lays the foundation for reshaping many fundamental s‐block metal‐mediated organic transformations in water.     

Stereoselective tribromomethylation of N-(tert-butanesulfinyl)imines with bromoform: practical synthesis of α-tribromomethyl amines

The unprecedented nucleophilic tribromomethylation of N-(tert-butanesulfinyl)imines with bromoform has been shown to be a highly stereoselective and practical method for the synthesis of enantiomerically pure α-tribromomethyl amines. THF has proven to be the best solvent in this addition reaction. By changing the reaction solvent from THF to DMF, 2,2-dibromoaziridines can also be synthesized directly from bromoform and N-(tert-butanesulfinyl)imines under similar reaction conditions.     

Reaction of N-arylcarbamoyl-1,4-benzoquinone imines with sodium azide

N-Arylcarbamoyl-1,4-benzoquinone imines reacted with sodium azide in completely regioselective fashion according to the 1,4-addition pattern with formation of 1-(3-azido-4-hydroxyphenyl)-3-arylureas. The reaction of N-arylcarbamoyl-2,6-dichloro-3,5-dimethyl-1,4-benzoquinone imines with sodium azide afforded N-arylcarbamoyl-2,6-diazido-3,5-dimethyl-1,4-benzoquinone imines as a result of nucleophilic substitution of the chlorine atoms.     

Stereoselective nucleophilic monofluoromethylation of N-(tert-butanesulfinyl)imines with fluoromethyl phenyl sulfone

[reaction: see text] Highly stereoselective nucleophilic monofluoromethylation of (R)-(tert-butanesulfinyl)imines with fluoromethyl phenyl sulfone was achieved to afford alpha-monofluoromethylamines with a nonchelation-controlled stereoselectivity mode. By using the same chemistry, (R)-(tert-butanesulfinyl)imines bearing a terminal tosylate (OTs) group can be converted to alpha-monofluoromethylated cyclic secondary amines with high stereoselectivity.     

A general organic catalyst for asymmetric addition of stabilized nucleophiles to acyl imines

Cinchona alkaloid-derived thiourea catalysts promote nucleophilic additions to acyl imines for the asymmetric synthesis of secondary amine adducts. The hydroquinine-derived thiourea catalyst efficiently promotes the aza-Henry reaction of nitroalkane with acyl imines, affording β-nitroamines in good yields with enantioselectivities of 90-98% ee and diastereoselectivities up to 97%. The scope of the reaction also includes dimethyl malonate as a nucleophile to access β-amino esters in high enantiopurity. Under the optimized reaction conditions, secondary amine adducts of high enantiopurity are generated based on various aromatic and α,β-unsaturated acyl imines.     

Reaction of <Emphasis Type="Italic">N</Emphasis>-chloro-1,4-benzoquinone imines with thiols

N-Chloro-1,4-benzoquinone imines reacted with arenethiols to give different products, depending on the conditions and initial quinone imine structure. N-(Arylsulfanyl)-1,4-benzoquinone imines were obtained as a result of nucleophilic substitution of the chlorine atom, and 1,4-benzoquinone imines containing an aryl-sulfanyl substituent in the quinoid ring were formed according to the radical mechanism. The reactions of N-chloro-1,4-benzoquinone imines with heterocyclic thiols afforded only the corresponding chlorine substitution products.     

Sequential catalytic process: synthesis of quinoline derivatives by AuCl3/CuBr-catalyzed three-component reaction of aldehydes, amines, and alkynes

A sequential catalytic process has been developed based on gold-catalyzed nucleophilic addition of terminal alkynes to imines, and gold-catalyzed intramolecular reaction of aromatic ring to alkynes. This one-pot reaction of aldehydes, amines, and alkynes gives quinoline derivatives in good yields.     

Phosphine-catalyzed annulations of azomethine imines: allene-dependent [3 + 2], [3 + 3], [4 + 3], and [3 + 2 + 3] pathways

In this paper we describe the phosphine-catalyzed [3 + 2], [3 + 3], [4 + 3], and [3 + 2 + 3] annulations of azomethine imines and allenoates. These processes mark the first use of azomethine imines in nucleophilic phosphine catalysis, producing dinitrogen-fused heterocycles, including tetrahydropyrazolo-pyrazolones, -pyridazinones, -diazepinones, and -diazocinones. Counting the two different reaction modes in the [3 + 3] cyclizations, there are five distinct reaction pathways-the choice of which depends on the structure and chemical properties of the allenoate. All reactions are operationally simple and proceed smoothly under mild reaction conditions, affording a broad range of 1,2-dinitrogen-containing heterocycles in moderate to excellent yields. A zwitterionic intermediate formed from a phosphine and two molecules of ethyl 2,3-butadienoate acted as a 1,5-dipole in the annulations of azomethine imines, leading to the [3 + 2 + 3] tetrahydropyrazolo-diazocinone products. The incorporation of two molecules of an allenoate into an eight-membered-ring product represents a new application of this versatile class of molecules in nucleophilic phosphine catalysis. The salient features of this protocol--the facile access to a diverse range of nitrogen-containing heterocycles and the simple preparation of azomethine imine substrates--suggest that it might find extensive applications in heterocycle synthesis.     

Supramolecular catalysis of Strecker reaction in water under neutral conditions in the presence of beta-cyclodextrin

An environmentally benign and highly efficient procedure for the nucleophilic addition of trimethylsilyl cyanide to imines (Strecker reaction) has been developed under biomimetic conditions in water in the presence of beta-cyclodextrin to afford alpha-aminonitriles in quantitative yields. The use of cyclodextrin precludes the use of either acid or base, and the catalyst can be recycled a number of times without loss in activity.     

Electrochemical synthesis and mechanestic study of quinone imines exploiting the dual character of N,N-dialkyl-p-phenylenediamines

Two one-pot electrochemical approaches for the synthesis of similar quinone imines via either the nucleophilic character of N,N-dialkyl-p-phenylenediamines or electrophilic reactivity of their oxidized forms through Michael-type addition reactions are reported.     

Palladium‐Catalyzed Carbonylative Difunctionalization of C=N Bond of Azaarenes or Imines to Quinazolinones

Supporting information for this article is given via a link at the end of the document. By intercepting the acylpalladium species with C=N bond of azaarenes or imines other than free amines or alcohols, the difunctionalization of C=N bond was established via palladium‐catalyzed carbonylation/nucleophilic addition sequence. This method is compatible with a diverse range of azaarenes and imines and allows for the efficient synthesis of a wide range of quinazolinones and derivatives. The synthetic utility has been demonstrated by one‐step synthesis of evodiamine and its analogue with inexpensive starting materials.     

Relay catalysis by a metal-complex/Brønsted acid binary system in a tandem isomerization/carbon-carbon bond forming sequence

A one-pot tandem isomerization/carbon-carbon bond forming sequence catalyzed by a ruthenium complex/Br?nsted acid binary system is demonstrated. The method enables the use of readily available allylamides to deliver reactive imines under relay catalysis using a binary catalytic system. Subsequent Br?nsted acid catalyzed carbon-carbon bond forming reactions of the generated imines with nucleophilic components afforded Friedel-Crafts and Mannich products in good yields.     

Orthoacylimines: a new class of chiral auxiliaries for nucleophilic addition of organolithium reagents to imines

A new class of orthoacylimine-derived chiral auxiliaries has been synthesized and tested in the nucleophilic addition of organolithium reagents to imines. The precursors can be prepared by an aza-Wittig reaction between the corresponding orthoacyl azide and a variety of aldehydes in the presence of trialkylphosphines. The nucleophilic addition of organolithium reagents led to the addition products in good yields and with good to excellent diastereoselectivities (from 85:15 to 99:1). The chiral, nonracemic secondary amines could be readily obtained under mild hydrolytic condition. Furthermore, the chiral auxiliary can be recovered in quantitative yield and reconverted to the starting orthoacyl azide precursor. This method was applied to the synthesis of (S)-t-leucine.     

Atroposelective Synthesis of 3,3’‐Bisindoles Bearing Axial and Central Chirality: Using Isatin‐Derived Imines as Electrophiles

An atroposelective synthesis of a new class of 3,3’‐bisindoles bearing axial and central chirality has been established via catalytic asymmetric addition reactions using isatin‐derived imines as electrophiles (23 examples, up to 80% yield, > 95 : 5 dr, 98 : 2 er). This approach takes advantage of chiral phosphoric acid‐catalyzed dynamic kinetic resolution of 2‐substituted 3,3’‐bisindoles via nucleophilic addition of such substrates with isatin‐derived imines. In this approach, isatin‐derived imines acted as a class of competent electrophiles due to their high reactivity and bulky size, which provided an easy access to axially chiral 3,3'‐bisindoles incorporated with a biologically important chiral 3‐aminooxindole unit. This approach has greatly expanded the generality and applicability of the strategy of dynamic kinetic resolution for the synthesis of enantioenriched 3,3’‐bisindole derivatives bearing both axial and central chirality.