Hydroboration d'amines insaturees—II: Régio et stéréosélectivité de l'hydroboration-alkylation d'amines acétyléniques

The hydroboration reaction of acetylenic amines R¹R²NCH(R³)CCR⁴ was studied. We report the first results of a study of the reactivity of dialkylborane R₂BH towards these amines which allow us to propose a new method for the synthesis of differently substituted β-ethylenic amines. The regioselectivity and the stereoselectivity of this reaction are examined and allow us to set out the possibility of a trans hydroboration.     

Deep eutectic solvent promoted highly efficient synthesis of N,N’-diarylamidines and formamides

A deep eutectic solvent was used as a dual catalyst and reaction medium for the efficient N-formylation of aromatic amines without hazardous organic solvent and catalyst. Treatment of aromatic amines with trimethyl orthoformate and formic acid in deep eutectic solvent at 70 °C gives the corresponding N-formyl derivatives in good to excellent yields. This simple ammonium deep eutectic solvent, easily synthesized from choline chloride and SnCl₂, with 100% atom economy and making it applicable to industry and laboratory. Furthermore, heating the trimethyl orthoformate and aromatic primary amines in the deep eutectic solvent results in formation of the corresponding N,N’-diarylamidines in high yields.     

N-Benzyloxycarbonylation of amines in the ionic liquid [TPA][l-Pro] as an efficient reaction medium

An efficient method for the N-benzyloxycarbonylation of amines is described. The reaction of amines with Cbz-Cl in the ionic liquid [TPA][l-Pro] afforded the corresponding N-Cbz derivatives in excellent yields. The method is versatile for the preparation of a wide variety of N-Cbz derivatives of aliphatic and aromatic amines.     

Convenient method for the synthesis of C-phosphorylated N-arylformamidines

C-Phosphorylated (P^V) arylformamidines have been prepared by the reaction of N-arylamidotrichloromethyl derivatives of phosphorus, thiophosphorus, and selenophosphorus acids with secondary amines. Dependence of the reaction on the nature of chalcogene, electronic and steric factors has been studied. By reduction of N-arylformamidinophosphonoselenides the corresponding C-phosphorylated (P^III) arylformamidines have been synthesized.     

High-performance liquid chromatography of 5,7-dinitrobenzofurazan and nitrobenzodifurazan derivatives of aromatic amines

The retention times of 5,7-dinitrobenzofurazan and nitrobenzodifurazan derivatives of aromatic amines in reversed-phase high-performance liquid chromatography on a column filled with Hypersil ODS correlate with the acidity constants of these derivatives in dimethyl sulfoxide (DMSO) and dimethylformamide (DMF) and with the σ constants of substituents in the aromatic nucleus. Procedures were developed for the determination of aniline, N-methylaniline, N,N-dimethylaniline, and N-ethylaniline as their 5,7-dinitrobenzofurazan and nitrobenzodifurazan derivatives with detection limits of 70 μg/mL. The procedures can be used for the analysis of reaction mixtures in the synthesis of these substituted amines.     

High regioselectivity in electrochemical α-methoxylation of N-protected cyclic amines

N-Protecting groups of α-substituted cyclic amines strongly affected the regioselectivity in electrochemical methoxylation of these compounds. Namely, N-acyl derivatives were transformed into α′-methoxylated compounds, while N-cyano derivatives changed into α-methoxylated derivatives. Furthermore, Lewis acid catalyzed nucleophilic substitution of the α-methoxylated compounds protected with cyano group afforded α,α-disubstituted cyclic amines.     

Amberlyst-15: a mild, efficient and reusable heterogeneous catalyst for N-tert-butoxycarbonylation of amines

A mild and versatile method has been developed for the chemoselective N-tert-butoxycarbonylation of amines in the presence of Amberlyst-15 under solvent-free condition. The method is general for the preparation of N-Boc derivatives of aliphatic (acyclic and cyclic) and aromatic amines.     

Arylation of adamantanamines: VI. Palladium-catalyzed arylation of amines and diamines of the adamantane series with 3-bromopyridine

Palladium-catalyzed amination of 3-bromopyridine with amines of the adamantane series in the presence of Pd(dba)₂/L [L = 2,2′-bis(diphenylphosphino)-1,1′-binaphthyl or 2-dimethylamino-2′-dicyclohexylphosphinobiphenyl] gave the desired N-(pyridin-3-yl)-substituted amines in 74–97% yields. Diamines of the adamantane series reacted with 2 equiv of 3-bromopyridine in a complicated fashion to produce mono- and triaryl-substituted derivatives as by-products, while the yields of N,N′-diarylation products were 18–56%.     

A mild and efficient chemoselective protection of amines as N-benzyloxycarbonyl derivatives in the presence of La(NO3)3·6H2O under solvent-free conditions

A facile and versatile method for the chemoselective N-benzyloxycarbonylation of amines has been developed by treatment with benzyloxycarbonyl chloride (Cbz-Cl) in the presence of lanthanum(III) nitrate hexahydrate under solvent-free conditions. The method is general for the preparation of N-Cbz derivatives of aliphatic (acyclic and cyclic) and aromatic amines.     

Mössbauer studies on ferrocene complexes: XVI. Structure of triorganostannyl derivatives of dimethylaminomethylferrocene and N,N-dimethylbenzylamine

A series of new stannylated derivatives of dimethylaminomethylferrocene (DMAMF) and N,N-dimethylbenzylamine have been synthesised and their structures investigated by ¹H, ¹³C and ¹¹⁹Sn NMR together with ⁵⁷Fe and ¹¹⁹Sn Mössbauer spectroscopy. Polystannylated derivatives were synthesised from DMAMF and BuLi in the presence of TMED. The methylene protons of the CH₂NMe₂ group were diastereotopic for all the DMAMF derivatives synthesised. The chemical shift differences of these protons is discussed in terms of conformational changes. ¹³C and 119Sn shifts were used to establish the substitution patterns in the polystannylated derivatives. ¹³C shifts for the 2-substituted derivatives of both DMBA and DMAMF were reasonably additive, for both the free amines and the quaternary ammonium salts. The Mössbauer data show no evidence of pentacoordination in any of the derivatives.     

N,N-1,2-Benzenedisulfonylimide,a new cyclic leaving group for the stereoselective nucleophilic substitution of amines

We hereby report the preparation and nucleophilic substitutions of the N,N-1,2-benzenedisulfonylimide derivatives 1a and 2a of the chiral amines 1 and 2. The nucleophilic attack of KNO₂ afforded the respective alcohols 3 and 4 with 84–90% inversion of configuration. Nucleophilic attack by the azide ion afforded the azide products 5 and 6 which were reduced to the corresponding inverted amines 1 and 2 (94–98.5% inversion). The improved leaving group ability of the N,N-1,2-benzenedisulfonylimides compared with previously reported N,N-disulfonylimides is discussed. Chiral GLC analysis of all products is summarized and the alternative chiral analysis of product 3 by ¹³C NMR using heptakis(2,3,6-tri-O-methyl)-β-cyclodextrin as a chiral solvating agent (CSA) is discussed.     

An umpolung approach to the hydroboration of pyridines: a novel and efficient synthesis of N-H 1,4-dihydropyridines

The first inverse hydroboration of pyridine with a diboron(4) compound and a proton source has been realized under simple basic and catalyst-free conditions. This process consists of a formal boryl anion addition to pyridine, which produces an N-boryl pyridyl anion complex, and the subsequent protonation of the anion complex. This process enables a simple and efficient method for the synthesis of multi-substituted N-H 1,4-dihydropyridine (1,4-DHP) derivatives that are difficult to prepare using established methods. Furthermore, this method allows for facile preparation of 4-deuterated 1,4-DHPs from an easily accessible deuterium ion source. This inverse hydroboration reaction represents a new mode for pyridine functionalization.

Umpolung of pyridine hydroboration was achieved by the reaction between pyridine and diboron(4) with a base and a proton source.     

Mechanistic Insight into Hydroboration of Imines from Combined Computational and Experimental Studies

Boron Lewis acid-catalyzed and catalyst-free hydroboration reactions of imines are attractive due to the mild reaction conditions. In this work, the mechanistic details of the hydroboration reactions of two different kinds of imines with pinacolborane (HBpin) are investigated by combining density functional theory calculations and some experimental studies. For the hydroboration reaction of N-(α-methylbenzylidene)aniline catalyzed by tris[3,5-bis(trifluoromethyl)phenyl]borane (BAr^F₃), our calculations show that the reaction proceeds through a boron Lewis acid-promoted hydride transfer mechanism rather than the classical Lewis acid activation mechanism. For the catalyst- and solvent-free hydroboration reaction of imine, N-benzylideneaniline, our calculations and experimental studies indicate that this reaction is difficult to occur under the reaction conditions reported previously. With a combination of computational and experimental studies, we have established that the commercially available BH₃ ⋅ SMe₂ can serve as an efficient catalyst for the hydroboration reactions of N-benzylideneaniline and similar imines. The hydroboration reactions catalyzed by BH₃ ⋅ SMe₂ are most likely to proceed through a hydroboration/B−H/B−N σ-bond metathesis pathway, which is very different from that of the reaction catalyzed by BAr^F₃.     

A green,isocyanide-based three-component reaction approach for the synthesis of multisubstituted ureas and thioureas

A one-pot, isocyanide based multicomponent protocol was presented starting from secondary amines towards (thio)urea derivatives and utilized for the construction of a diverse 27-membered chemical library. Following a green compatible microwave assisted condition, the formed N,N′-multisubstituted (thio)ureas were obtained in up to 85% yield.     

Synthesis of tetrahydrophthalazine and phthalamide (phthalimide) derivatives via palladium-catalysed carbonylation of iodoarenes

1,2,3,4-Tetrahydrophthalazin-1-one and 1,2,3,4-tetrahydrophthalazin-1,4-dione derivatives were synthesised in high (up to 85%) and low yields using 2-iodobenzyl bromide and 1,2-diiodobenzene as bifunctional substrates, respectively. Iodoarenes, carbon monoxide and various hydrazine derivatives as N-nucleophiles were used in a three-component palladium-catalysed cascade hydrazinocarbonylation. A similar palladium-catalysed reaction, the aminocarbonylation of 1,2-diiodobenzene, resulted mainly in the formation of two types of major products depending on the amine N-nucleophiles: the use of primary amines yielded N-substituted phthalimides in double carbonylation, while secondary amines react with one of the iodoarene functionalities affording the corresponding 2-iodobenzamides. Due to double carbon monoxide insertion at one or both iodoarene functionalities, ketocarboxamide-carboxamide or bis-ketocarboxamide derivatives could be isolated by the modification of the reaction conditions. Some mechanistic details of the ring-closure reactions and the conditions leading to side-products are also discussed.     

N-(Benzoyloxy)amines: an investigation of their thermal stability, synthesis, and incorporation into novel peptide constructs

A series of N-benzoyloxyamines were pyrolyzed and their decomposition temperatures correlated well with the amine architecture's ability to stabilize a N-centered radical. A variety of amine substrates were treated with a biphasic mixture of benzoyl peroxide (BPO), CH₂Cl₂ and an aqueous carbonate buffer (at pH 10.5). Primary and secondary amines were successfully N-benzoyloxylated in good yield. Tertiary amines and BPO gave low yields of the corresponding N-oxide and complex product mixtures, presumably via radical decomposition. Electron deficient amines (such as fluorinated aliphatic amines, α-aminoacids, α-aminoesters, and α-aminoamides) were not N-benzoyloxylated under these conditions. Instead, N-benzoylation was observed with the fluorinated amines and the reaction was sensitive to temperature and the pH of the aqueous medium. A one-pot-two-step synthesis of N^α-FMOC-l-Leu-N^β-(benzoyloxy)-β-alanine ethyl ester, a peptide containing both an α- and a novel β-amino acid framework, was also developed.     

Synthesis of enantiomerically-enriched N-aryl amino-amides via a Jocic-type reaction

Enantiomerically-enriched secondary trichloromethyl-alcohols react with aryl amines to give enantiomerically-enriched α-N-arylamino-acid derivatives. The intermediate acid chlorides can react in situ with aryl or, regioselectively, with alkyl amines to give aryl or alkyl α-N-arylamino amides.     

Estimation of absorption band contribution for overtones and combined frequencies in the fingerprint region for alkanes, nitriles, amines, and nitroalkanes

In the anharmonic approximation the intensities of fundamental, overtone, and combined absorption bands are calculated in the range from 100 cm^-1 to 4000 cm^-1 for a series of alkanes, nitriles, amines, and nitroalkanes. The first and second derivatives of the molecular dipole moment are calculated by quantum chemical methods in the ab initio approximation using the MP2/6-31G(1d) basis set. Overtones and combined frequencies are found to make a significant contribution (5–20%) to the total absorption. The spectral distribution of this contribution depends on the molecular structure. For nitriles and amines significant absorption of the overtones and combined frequencies is observed in the same regions where fundamental absorption bands characteristic of these compounds are located.     

Aminomethylation of N-methylmorpholinium 6-amino-4-aryl-3,5-dicyano-1,4-dihydropyridine-2-selenolates as an approach to the preparation of 3,5,7,11-tetraazatricyclo[7.3.1.02,7]tridec-2-ene-8-selenone derivatives

A reaction of N-methylmorpholinium 6-amino-4-aryl-3,5-dicyano-1,4-dihydropyridine-2-selenolates with primary amines and excess of formaldehyde leads to 3,5,7,11-tetraazatricyclo[7.3.1.0^2,7]tridec-2-ene-8-selenone derivatives. The same compounds were obtained by a multicomponent cascade cyclocondensation of benzaldehyde, cyanoselenoacetamide, primary amine, and excess of formaldehyde.     

New organic activators for the enantioselective reduction of aromatic imines with trichlorosilane

N-Picolinoyl-(2S)-(diphenylhydroxymethyl)pyrrolidine was found to work as an organic activator in the reduction of aromatic imines to the corresponding amines by Cl₃SiH. The highest selectivity was 80% ee. These are the first data showing that N-formyl group is not always essential as N-protecting group of pyrrolidine derivatives for the reduction of imines by Cl₃SiH.