Catalytic Enantioselective Reaction of α‐Aminoacetonitriles Using Chiral Bis(imidazoline) Palladium Catalysts

The catalytic enantioselective reaction of diphenylmethylidene‐protected α‐aminoacetonitriles with imines has been developed. Good yields and diastereo‐ and enantioselectivities were observed for the reaction of various imines using chiral bis(imidazoline)/Pd catalysts. The reaction of α‐aminonitriles with di‐tert‐butyl azodicarboxylate afforded chiral α,α‐diaminonitriles in high yields with high enantioselectivities.     

Synthesis and structure of N-alkyl(aryl)aminocarbonyl-1,4-benzoquinone imines

New N-alkyl(aryl)aminocarbonyl-1,4-benzoquinone imines were synthesized by reaction of isocyanates with the corresponding substituted 4-aminophenols, and their structure was determined on the basis of ¹H and ¹³C NMR spectra and X-ray diffraction data.     

Metal-free catalytic hydrogenation of imines with tris(perfluorophenyl)borane

Metal-free homogeneous catalysed hydrogenation of various imines was accomplished with tris(perfluorophenyl)borane under moderate reaction conditions.     

Thioether-based copper(I) Schiff base complex as a catalyst for a direct and asymmetric A3-coupling reaction

A novel thiosalen ligand based on a thioether has been prepared and readily coordinated with copper(I) salts (CuCl, CuBr, CuI, and CuCN). The new organometallic catalyst was used for the direct and enantioselective alkynylations of imines in an A³-coupling reaction. In this reaction, the corresponding propargylamines were obtained as single products in excellent yields and with good enantioselectivities.     

Catalytic Enantioselective Reaction of α‐Phenylthioacetonitriles with Imines Using Chiral Bis(imidazoline)–Palladium Catalysts

The catalytic enantioselective reaction of α‐phenylthioacetonitriles with imines has been developed. The reaction of various imines proceeds in good yields and diastereo‐ and enantioselectivities in the presence of chiral bis(imidazoline)–palladium catalysts. The obtained products can be converted into β‐aminonitrile or β‐aminoamide compounds without loss of enantiopurity.     

Generation and metathesis of azomethine imines in reaction of 6-aryl-1,5-diazabicyclo[3.1.0]hexanes with het(aryl)methylidenemalononitriles

A new metathesis reaction of azomethine imines is found. Catalytic or thermal diaziridine ring opening of 6-aryl-1,5-diazabicyclo[3.1.0]hexanes leads to azomethine imines reacting further with het(aryl)methylidenemalononitriles to give in situ new azomethine imines inaccessible by common synthetic methods. New azomethine imines are detected as pyrazolines formed via a 1,4-H shift and trapped by the [3+2] cycloaddition with various dipolarophiles to yield 1,5-diazabicyclo[3.3.0]octane derivatives bearing pharmacophoric heterocycles, e.g. furan, nitrofuran, thiophene, and indole. The best results are achieved in the Et₂O·BF₃-catalyzed reactions in ionic liquids.     

Nickel(0)‐Catalyzed Hydroalkenylation of Imines with Styrene and Its Derivatives

A nickel(0)‐catalyzed hydroalkenylation of imines with styrene and its derivatives is described. A wide range of aromatic and aliphatic imines directly coupled with styrene and its derivatives, thus providing various synthetically useful allylic amines with up to 95 % yield. The reaction offers a new atom‐ and step‐economical approach to allylic amines by using alkenes instead of alkenyl‐metallic reagents. Experiments and DFT calculations showed that TsNH₂ promotes the proton transfer from the coordinated olefin to the imine, accompanied by a new C?C bond formation.     

Synthesis and Characterization of O,O-Dimethyl-N-(2,2,2-trichloro-1-arylaminoethyl) Phosphoramidothioates

Several novel trichloromethyl-containing O,O-dimethyl phosphoramidothioate derivatives have been synthesized by the reaction of O,O-dimethyl phosphoramidothioate with chloral imines. The latter were prepared in good yields by refluxing the dichloroethane solution of chloral and substituted anilines using 3 Å molecular sieves as dehydrating agent. Structures of title compounds were confirmed by IR, ¹H NMR, ³¹P NMR, and FT-MS studies.     

Highly Stereoselective Cobalt(III)‐Catalyzed Three‐Component C−H Bond Addition Cascade

A highly stereoselective three‐component C(sp²)?H bond addition across alkene and polarized π‐bonds is reported for which Co^III catalysis was shown to be much more effective than Rh^III. The reaction proceeds at ambient temperature with both aryl and alkyl enones employed as efficient coupling partners. Moreover, the reaction exhibits extremely broad scope with respect to the aldehyde input; electron rich and poor aromatic, alkenyl, and branched and unbranched alkyl aldehydes all couple in good yield and with high diastereoselectivity. Multiple directing groups participate in this transformation, including pyrazole, pyridine, and imine functional groups. Both aromatic and alkenyl C(sp²)?H bonds undergo the three‐component addition cascade, and the alkenyl addition product can readily be converted into diastereomerically pure five‐membered lactones. Additionally, the first asymmetric reactions with Co^III‐catalyzed C?H functionalization are demonstrated with three‐component C?H bond addition cascades employing N‐tert‐butanesulfinyl imines. These examples represent the first transition metal catalyzed C?H bond additions to N‐tert‐butanesulfinyl imines, which are versatile and extensively used intermediates for the asymmetric synthesis of amines.     

Rhodium(II) catalyzed multi-component reactions of aryldiazoacetates with titanium(IV) isopropoxide and imines

Rh₂(OAc)₄ catalyzed diazo decomposition of aryldiazoacetates in the presence of titanium(IV) isopropoxide generated oxonium ylide intermediates. Trapping of the oxonium ylide intermediates with imines occurred subsequently via a nucleophilic addition. The three-component reaction of aryldiazoacetates, titanium(IV) isopropoxide, and imines gave α-alkoxyl-β-amino acid derivatives with C-N/C-C bond formation in a single step. Extension of the study to a four-component reaction with in situ generated imine was also investigated.     

N-(Alkylsulfamoyl)aldimines: easily deprotected precursors for diarylmethylamine synthesis

The sequential reaction of chlorosulfonyl isocyanate with t-BuOH, t-BuNH₂ and TFA allows formation of H₂NSO₂NHBu^t. Condensation of the latter with Ar¹CHO in the presence of Ti(OEt)₄ provides the activated imines Ar¹CHNSO₂NHBu^t (59–89%). Commercially available boronic acids add to these imines with good stereoselectivity (76–98% ee) using readily available diene ligands. Simple deprotection with 5% w/w water in pyridine affords free Ar¹CHNH₂Ar².     

Synthesis,Characterization, and Structure of Quinoline‐based Benzimidazole Derivatives

Quinoline‐based benzimidazole compounds have been successfully synthesized and characterized by various spectroscopic techniques like FT‐IR, ¹H NMR, ¹³C NMR, and mass spectral analysis, and the structures have been authenticated by single crystal X‐ray diffraction method. Here, we report an economical, mild, and efficient procedure that involves condensation of 8‐hydroxyquinoline‐2‐carbaldehyde with various diamines as substrates to give bis‐imines. A systematic study towards both aliphatic and aromatic bis‐imines has been conducted to investigate the ring‐closure reaction that generates the benzimidazole moiety in the heterocyclic compounds discussed in this study. Aliphatic bis‐imines does not undergo cyclization; however, the bis‐imines derived from o‐phenylenediamine and derivatives generates heterocyclic compounds with benzimidazole moiety. In contrast to synthetic procedures reported earlier for benzimidazoles, the reaction conditions herein reported are simpler. Path for reactions holds initial condensation with one equivalent of 8‐hydroxyquinoline‐2‐carbaldehyde to form mono‐imine followed by immediate intramolecular ring closure. The subsequent nupleophilic attack to another equivalent of 8‐hydroxyquinoline‐2‐carbaldehyde and migration of hydride generates the benzimidazole moiety and the active methylene group. The ─CH₂ group was confirmed from ¹H and ¹³C NMR, wherein the two hydrogens appeared at around 6.40–6.52 ppm and the carbon center appeared at 51.54–51.77 ppm. The single crystal X‐ray diffraction also confirmed the formation of benzimidazole moiety and the active methylene group in the heterocyclic compounds discussed in this study.     

Microwave-assisted synthesis of rhodamine derivatives

The microwave synthesis of 12 rhodamine-derived imines is described. The present work involves condensation of rhodamine hydrazide with various aromatic aldehydes in ethanol under microwave irradiation. The results obtained indicate that, unlike classical heating, microwave irradiation results in higher yields, shorter reaction time, mild reaction condition and simple work-up procedure. The structures of synthesized compounds were confirmed by ¹H-NMR, ¹³C-NMR, FT-IR and high-resolution mass spectra data.     

Catalytic,asymmetric Strecker reactions catalysed by titaniumIV and vanadiumV(salen) complexes

Vanadium^V(salen) complex 3 has been found to be an effective catalyst for the asymmetric addition of hydrogen cyanide (generated in situ from trimethylsilyl cyanide) to imines. The best results (up to 81% enantiomeric excess) were obtained for aromatic imines in which the nitrogen atom is protected with a benzyl group and in which the imine bond is not sterically encumbered.     

Gas-phase reactions of the bis(η-cyclopentadienyl)methylzirconium cation with imines

The reactions of the bis(η⁵-cyclopentadienyl)methylzirconium cation (1) with four imines have been studied in the gas phase by Fourier transform ion cyclotron resonance mass spectrometry. Reactivity of the bis(η⁵-cyclopentadienyl)methylzirconium cation is governed by the availability of a labile hydrogen in the corresponding imine. The products observed differ from those that might be expected in analogy with earlier work on ketones, aldehydes and alkenes (e.g., zirconocene η³-enolate and η³-allyl complexes): azomethyne/benzylidene species are found instead of enamines; however, the general reaction mechanism resembles that proposed for ketones and alkenes. An elimination reaction leading to final products was shown to be preceded by a fast migratory insertion/deinsertion equilibrium for alkyl-substituted imines. Such an equilibrium is not possible for aryl-substituted imines due to lack of lability of the aryl groups and thus only methane elimination was observed for these imines.     

Novel β-hydroxy-β-bis(trifluoromethyl) imines

Selected imines reacted with hexafluoroacetone non-catalyzed at ambient temperature to give β-hydroxy-β-bis(trifluoromethyl) imines in good to excellent yields. For the imines of acetone, pentan-3-one, and of cyclohexanone a 1:2 reaction was observed giving iminodiols; for N,N′-bis(propylidene)ethylene diamine an iminotetrol was formed. The diol derivative of N-isopropyl-propylidene amine could be deprotonated and O-methylated furnishing the respective ethers. Hexafluoropropylidene amine reacted with N-isopropyl-propylidene amine, unlike hexafluoroacetone, in a 1:1 manner to form an amino-imino alcohol which in its turn is able to add hexafluoroacetone. The imines of acetophenone, trifluoroacetone, 2,4-dimethyl-pentan-3-one, 2,6-dimethyl-cyclohexanone and of acetaldehyde added hexafluoroacetone to furnish β-iminoalcohols. A multifunctional β-hydroxy enaminone was obtained from 4-isopropylamino-pent-3-en-2-one. The molecular structures of the novel β-hydroxy-β-bis(trifluoromethyl) imines exhibit strong (R)N?HO hydrogen bonds.     

A new route towards N-(α-methoxybenzyl)aziridines

A new synthesis of N-(α-methoxyarylmethyl)-2,2-dimethylaziridines is presented. Different benzaldehydes were converted into the corresponding imines upon reaction with 2-bromo-2-methylpropylamine. Treatment of the latter imines with sodium methoxide afforded N-(α-methoxyarylmethyl)-2,2-dimethylaziridines in good yields.     

Umsetzung von N-Trimethylmetall(IVb)-trialkylphosphiniminen mit Halogenwasserstoffen

Reaction of N-Trimethylmetal(IVb) Trialkylphosphine Imines with Hydrogen Halides Investigations of the reaction of N-trimethylmetal(IVb)-substituted phosphine imines with hydrogen have been carried out. With one mole of HX phosphonium halides of the general formula [R₃P? NH? MMe₃]^⊕X^? (R = CH₃, C₂H₅; M = Si, Ge, Sn; X = Cl, Br, J) are obtained. A second mole of HX causes M? N bond cleavage, yielding aminophosphonium halides, [R₃P? NH₂]^⊕X^?.     

Insertion reactions of trans-Mo(dmpe)2(H)(NO) with imines

The insertion chemistry of the hydride complex trans-Mo(dmpe)(2)(H)(NO) (1) (dmpe = bis(dimethylphosphino)ethane) with imines has been investigated. It was found that disubstituted aromatic imines RCH[double bond]NR' (R, R' = Ar) insert into the Mo-H bond of 1, while a series of various mono- and other disubstituted imines do not react. The insertion products trans-Mo(dmpe)(2)(NO)[NR'(CH(2)R)] (R = R' = Ph (2); R = Cp(2)Fe, R' = Ph (3); R = Ph, R' = Cp(2)Fe (4); R = 1-naphthyl, R' = Ph (5)) have been isolated and fully characterized by elemental analysis, IR and NMR spectroscopy, and mass spectrometry. The imine PhCH[double bond]NC(10)H(7) (C(10)H(7) = 1-naphthyl) reacted with 1 establishing an equilibrium to produce the nonisolable complex trans-Mo(dmpe)(2)(NO)[NC(10)H(7)(CH(2)Ph)] (6). The equilibrium constant for this reaction has been derived from VT-NMR measurements, and the Delta H and Delta S values of this reaction were calculated to be -48.8 +/- 0.4 kJ.mol(-1) and -33 +/- 1 J.K(-1).mol(-1) reflecting a mild exothermic process and its associative nature. Single-crystal X-ray diffraction analyses were carried out on 2-5.     

Diastereoselective synthesis of cyclic 1,3-aminoalcohols bearing CF3(CCl3)-groups

An aldol-type reaction of cyclic imines and cyclic lactims with carbonyl compounds activated by electron withdrawing trifluoromethyl or trichloromethyl groups proceeded without any catalyst under mild condition. β-Hydroxymethyl substituted cyclic imines or imidates are formed as a result of the reaction. The reduction of the prepared imines leads stereoselectively to the cyclic 1,3-aminoalcohols. Application of methyl trifluoropyruvate in this transformation opens an opportunity for the synthesis of γ-aminoacids derivatives which contain pyrrolidine moiety.