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Search for "imines" in Full Text gives 250 result(s) in Beilstein Journal of Organic Chemistry. Showing first 200.
Organobase-catalyzed three-component reactions for the synthesis of 4H-2-aminopyrans, condensed pyrans and polysubstituted benzenes
Beilstein J. Org. Chem. 2014, 10, 141–149, doi:10.3762/bjoc.10.11
- subsequently cyclizes to produce 18. It is of value to note that, when the reaction of 14 and 15 is conducted in the absence of malononitrile, dihydroquinolinone 21 is generated through a pathway involving the intermediate imines 19 and 20 (Scheme 5). The structure of 21 was determined by X-ray
Studies on the interaction of isocyanides with imines: reaction scope and mechanistic variations
Beilstein J. Org. Chem. 2014, 10, 12–17, doi:10.3762/bjoc.10.3
- Barcelona, Spain 10.3762/bjoc.10.3 Abstract The interaction of imines with isocyanides has been studied. The main product results from a sequential process involving the attack of two units of isocyanide, under Lewis acid catalysis, upon the carbon–nitrogen double bond of the imine to form the 4-membered
- ring system. The scope of the reaction regarding the imine and isocyanide ranges has been determined, and also some mechanistic variations and structural features have been described. Keywords: azetidines; heterocycles; imines; isocyanides; multicomponent reactions; Introduction The interaction of
- imines with isocyanides is mainly focused on to the well-known Ugi multicomponent reaction (MCR) [1]. This fundamental process features the participation of a carboxylic acid group which attacks the intermediate nitrilium ion thus leading, after the Mumm rearrangement, to α-amidoamides. However, the
Diastereoselectivity in the Staudinger reaction of pentafluorosulfanylaldimines and ketimines
Beilstein J. Org. Chem. 2013, 9, 2675–2680, doi:10.3762/bjoc.9.303
- control of the C–N ketimine geometry was reflected in the stereochemistry of the product β-lactam. Cyclization of imines with a stereogenic center bearing SF5 was reflected in the 1,2-lk,lk selectivity of the β-lactam. Keywords: aldimine; Cornforth transition state; diastereoselectivity; β-lactam; organo
- familiar Staudinger reaction of imines to transform readily accessible aldehydes to β-lactams has been well reviewed [30][31][32][33], yet in spite of this familiarity, the mechanism of this process remains a topic of interest [34][35][36]. Previously, it has been shown that fluorinated imines can undergo
- attributed to the equatorial fluorines of the imine 5a (δ 68.8 ppm) appearing upfield of those assigned to the aldehyde 1a (δ 72.4 ppm). In the case of imines 5b–d, the solution also contained between 15–20% of the putative enamine 6b–d, where, for example, the equatorial fluorine resonances of 6b appeared
Direct electrophilic N-trifluoromethylthiolation of amines with trifluoromethanesulfenamide
Beilstein J. Org. Chem. 2013, 9, 2354–2357, doi:10.3762/bjoc.9.270
- volatility, some compounds (3h and 3i) have not been isolated. Imines can be also trifluoromethylthiolated in good yields (3m). Even if our first developed method is compatible with primary amines [37], they can also react under these new conditions, as illustrated with the aniline (3n). Amino alcohols and
Micro-flow synthesis and structural analysis of sterically crowded diimine ligands with five aryl rings
Beilstein J. Org. Chem. 2013, 9, 2336–2343, doi:10.3762/bjoc.9.268
- this plane and was nearly perpendicular. The bond lengths for imines C(1)–N(1) and C(2)–N(3) were 1.273(4) and 1.278(4) Å, respectively, while the bond lengths for amines C(1)–N(2) and C(2)–N(2) were 1.420(4) and 1.421(4) Å, respectively. Reportedly, the two amine bond lengths were different in the
- this plane and was almost perpendicular. The bond lengths for imines C(1)–N(1) and C(2)–N(3) were 1.269(3) and 1.274(3) Å, respectively, while the bond lengths for amines C(1)–N(2) and C(2)–N(2) were 1.413(3) and 1.411(3) Å, respectively. The bond lengths for amines C(1)–N(2) and C(2)–N(2) were nearly
- character around the imines and amine nitrogen, respectively. A series of olefin polymerizations were briefly tested as shown in Table 2. Both catalysts 12 and 13 exerted high activity for the ethylene homopolymerization (Table 2, entries 1 and 2). As far as we could ascertain, neither propene
Bis(benzylamine) monomers: One-pot preparation and application in dendrimer scaffolds for removing pyrene from aqueous environments
Beilstein J. Org. Chem. 2013, 9, 2320–2327, doi:10.3762/bjoc.9.266
- composition. Keywords: amines; dendrimer; fluorescence studies; imines; pyrene; Introduction Highly-branched polymeric systems provide an attractive route for removing pollutants from water due to their interior cavities and their ease of formation [1]. While several promising approaches have been reported
- benzaldehydes that resulted in unstable imines. An unprecedented first-generation bisamine-based dendrimer 6 was prepared but was found to degrade readily in organic solvents. More stable second-generation dendrimers composed of hybrid dendrons 8 and one of the three tri-phenol cores 5, 9, and 10 were
Gold(I)-catalyzed enantioselective cycloaddition reactions
Beilstein J. Org. Chem. 2013, 9, 2250–2264, doi:10.3762/bjoc.9.264
- methods that affords optically active cyclooctanes by means of a catalytic enantioselective process. Also recently, Chen and co-workers demonstrated that gold-activated allenamide species can participate in [3 + 2] cycloadditions with azomethine imines or nitrones under catalysis with Ph3PAuCl/AgOTf or
An investigation of the observed, but counter-intuitive, stereoselectivity noted during chiral amine synthesis via N-chiral-ketimines
Beilstein J. Org. Chem. 2013, 9, 2103–2112, doi:10.3762/bjoc.9.247
- -2343, USA 10.3762/bjoc.9.247 Abstract The default explanation for good to high diastereomeric excess when reducing N-chiral imines possessing only mediocre cis/trans-imine ratios (>15% cis-imine) has invariably been in situ cis-to-trans isomerization before reduction; but until now no study
- unequivocally supported this conclusion. The present study co-examines an alternative hypothesis, namely that some classes of cis-imines may hold conformations that erode the inherent facial bias of the chiral auxiliary, providing more of the trans-imine reduction product than would otherwise be expected. The
- addition to imines [31][32] continue to be refined and relied on. Furthermore, enzymatic methods can offer competitive advantages that cannot be overlooked [33][34][35]. With this perspective, it is perhaps unsurprising that methods utilizing imines with chiral amine auxiliaries, i.e. N-chiral imines, can
The chemistry of amine radical cations produced by visible light photoredox catalysis
Beilstein J. Org. Chem. 2013, 9, 1977–2001, doi:10.3762/bjoc.9.234
- ] and Rueping [83] independently reported that N-arylglycine derivatives 65 are viable substrates (Scheme 16). They are presumably converted to imines 65a that are intercepted by indoles to give the Mannich-like adducts 67. The conditions used by Li were 10 mol % Ru(bpy)3Cl2 and 1 atm O2 at 40 °C with a
Synthesis of the reported structure of piperazirum using a nitro-Mannich reaction as the key stereochemical determining step
Beilstein J. Org. Chem. 2013, 9, 1737–1744, doi:10.3762/bjoc.9.200
- using (CF3CO)2O gave only β-nitroamine 16 as a single diastereoisomer in a low 15% yield. These results are consistent with the poor conversions and dr, as well as resistance to trifluoroacetamide protection, we have observed before from imines derived from α-branched aldehydes such as
An organocatalytic route to 2-heteroarylmethylene decorated N-arylpyrroles
Beilstein J. Org. Chem. 2013, 9, 1480–1486, doi:10.3762/bjoc.9.168
- high yield (91%). The Mannich coupling was next attempted with different imines 2b–e in order to modulate the nature of the aryl moiety (Scheme 4). The electronic nature of the aniline being crucial for the stability of the imine and the hydroamination step, electronically rich anilines were selected
- to form imines 2b,c. Hence, when imines 2b,c were exposed to aldehyde 1a in the presence of catalyst 6 (available in racemic form), the Mannich adducts 7i,j were obtained and directly reacted with phosphonium salt 3. In line with our procedure, the resulting acyclic anilines 8i,j were then exposed to
- limitation being the formation of the corresponding imines. Similarly, imine 2d prepared from para-bromoaniline was found to be unstable and only degradation was observed during the Mannich reaction. When imine 2e, derived from the para-iodoaniline, was engaged in the process, the hydroamination step turned
Dipolar addition to cyclic vinyl sulfones leading to dual conformation tricycles
Beilstein J. Org. Chem. 2013, 9, 1419–1425, doi:10.3762/bjoc.9.159
- Science Hall, Notre Dame, IN, 46556, USA 10.3762/bjoc.9.159 Abstract Dipolar addition of cyclic azomethine imines with cyclic vinyl sulfones gave rise to functionalized tricycles that exhibited fluxional behavior in solution at room temperature. The scope of the synthetic methodology was explored, and
- pathways are open to the reactants. The additional aromatic substituent in 7 (relative to 4) once again contributed to significant broadening in both the 1H and 13C NMR spectra. Conclusion Our results comprise the first syntheses of tricyclic sulfones by 1,3-dipolar cycloadditions of azomethine imines with
α-Bromodiazoacetamides – a new class of diazo compounds for catalyst-free, ambient temperature intramolecular C–H insertion reactions
Beilstein J. Org. Chem. 2013, 9, 1407–1413, doi:10.3762/bjoc.9.157
- ][27][28][29][30], as well as carbon, e.g., in aldol reactions with aldehydes [31][32], ketones [33][34] and imines [35][36]. The first syntheses of α-halodiazoacetic esters, reported in the late 1960s, employed electrophilic diazoalkane substitution; the mercury or silver salts of ethyl diazoacetate
A construction of 4,4-spirocyclic γ-lactams by tandem radical cyclization with carbon monoxide
Beilstein J. Org. Chem. 2013, 9, 1340–1345, doi:10.3762/bjoc.9.151
- -spirocyclic oxindole γ-lactams by the cycloaddition of imines and succinic anhydrides [5]. Tandem radical cyclization can also provide a powerful tool for the construction of heterocycles [6][7][8][9][10][11][12]. One of us previously reported on the construction of spirocyclic pyrrolidinyl oxindoles by the
Establishing the concept of aza-[3 + 3] annulations using enones as a key expansion of this unified strategy in alkaloid synthesis
Beilstein J. Org. Chem. 2013, 9, 1170–1178, doi:10.3762/bjoc.9.131
- handled vinylogous amides and vinyl iminium salts. It provides a significant complementary, if not superior, approach to aza-[4 + 2] cycloadditions in constructing piperidines, because the aza-dienes and imines required are not always the most accessible and/or easily handled substrates given the problems
Interplay of ortho- with spiro-cyclisation during iminyl radical closures onto arenes and heteroarenes
Beilstein J. Org. Chem. 2013, 9, 1083–1092, doi:10.3762/bjoc.9.120
- terminate rapidly at diffusion-controlled rates by N–N coupling to give azines [32]. β-Scission reactions yielding nitriles do occur, but are not important at T < ~420 K for aryliminyls or for iminyls with primary alkyl substituents [32]. The rate constants for H-abstraction by iminyls yielding imines are
- communicated previously, 3-substituted phenanthridines 10a–f were isolated in good to quantitative yields (52–99%, Scheme 1) irrespective of the nature of the 4-substituent [26]. No spiro-products were detected even by GC–MS analyses of reaction mixtures. Byproducts included traces of imines ArC(R2)=NH (ImH
3D-printed devices for continuous-flow organic chemistry
Beilstein J. Org. Chem. 2013, 9, 951–959, doi:10.3762/bjoc.9.109
- ]. Further, the use of such techniques may also be used to obtain quantitative information about reaction progress and to rapidly optimize the reaction conditions “on the fly”. First, an in-house designed and 3D-printed reactionware device was employed for the synthesis of imines from the reaction of a range
- imines under flow conditions. We monitored the reaction progress with the help of an in-line ATR-IR flow cell, which is a very useful technique for the monitoring of organic reactions under flow conditions [10][21][22][23][24][25][26]. The flow setup used for these syntheses consists of two syringe pumps
- connected with a length of tubing with a volume 0.1 mL to the IR flow cell. Hence, the total flow reactor volume (VR) was 0.5 mL. The syntheses of the imines were monitored by an in-line ATR-IR flow cell and were conducted at a total flow rate of 0.25 mL min−1, where two equimolar methanolic solutions of 1
Preparation and ring-opening reactions of N-diphenylphosphinyl vinyl aziridines
Beilstein J. Org. Chem. 2013, 9, 852–859, doi:10.3762/bjoc.9.98
- -diphenylphosphinyl vinyl aziridines are prepared by a reaction of N-diphenylphosphinyl imines with α-bromoallyllithium in the presence of freshly fused ZnCl2. These aziridines undergo a ring-opening reaction with a variety of carbon and heteronucleophiles, in good yield, and generally with good regioselectivity
- reported direct synthesis of a vinyl aziridine bearing a phosphorus group on nitrogen [40]. Encouraged by this promising result, we next examined the scope of the reaction by using the same anion and N-Dpp imines derived from 4-bromo- and 4-fluorobenzaldehyde, furfural and 2,2-dimethylpropionaldehyde
- . Disappointingly, the yields of aziridines 2–5 obtained from these reactions were poor (21–32%), though the diastereoselectivity of the transformation remained good (Table 1). All of the N-Dpp imines derived from aromatic aldehydes favoured the formation of (E)-vinyl aziridines, with diastereomeric ratios very
3-Pyridylnitrene, 2- and 4-pyrimidinylcarbenes, 3-quinolylnitrenes, and 4-quinazolinylcarbenes. Interconversion, ring expansion to diazacycloheptatetraenes, ring opening to nitrile ylides, and ring contraction to cyanopyrroles and cyanoindoles
Beilstein J. Org. Chem. 2013, 9, 743–753, doi:10.3762/bjoc.9.84
- to the formation of glutacononitriles in low yields [12]. In contrast, 3-pyridylnitrene (10) undergoes a different type of ring opening to the observable nitrile ylide 11 and subsequently the ketenimine 12 (Scheme 3) [13]. Nitrile imines [14] and nitrile ylides [15][16] may have either allenic or
Enantioselective reduction of ketoimines promoted by easily available (S)-proline derivatives
Beilstein J. Org. Chem. 2013, 9, 633–640, doi:10.3762/bjoc.9.71
- testing the commercially available N-Boc-L-proline (1) as catalyst in the reduction of ketimines with trichlorosilane. The imines were typically prepared with a microwave-promoted reaction between acetophenone and the aromatic amine in toluene in the presence of K10 clay as activator. The first screening
- substituted imines (Table 3). Catalyst 5 showed a good chemical activity, promoting the enantioselective reduction in yields up to 88%, except when a very bulky protecting group was used (Table 3, entry 4). In the reaction of both N-Ph and N-PMP imines derived from acetophenone a discrete level of
Carbolithiation of N-alkenyl ureas and N-alkenyl carbamates
Beilstein J. Org. Chem. 2013, 9, 628–632, doi:10.3762/bjoc.9.70
- imines 7 and 8 with di-tert-butyl dicarbonate or with (−)-menthylchloroformate (Scheme 4). The N-alkenylcarbamates 10 and 11 were formed exclusively as their E isomers, and the X-ray crystal structure of E-10 is shown in Figure 2. Vinyl carbamate 9 was treated with primary, secondary or tertiary
Titanium-mediated reductive cross-coupling reactions of imines with terminal alkynes: An efficient route for the synthesis of stereodefined allylic amines
Beilstein J. Org. Chem. 2013, 9, 621–627, doi:10.3762/bjoc.9.69
- Chemical Technology, Shenyang 110142, People’s Republic of China 10.3762/bjoc.9.69 Abstract Low-valency titanium species, generated in situ by using Ti(OiPr)4/2 c-C5H9MgCl reagent, react with imines to give a titanium-imine complex that can couple with terminal alkynes to provide azatitanacyclopentenes
- with excellent regioselectivity. Stereodefined allylic amines are obtained in good yields after hydrolysis or iodonolysis of the corresponding azatitanacyclopentenes. When ethynylcyclopropane is used as the coupling partner to react with imines in this reaction, the initially generated allylic amine
- ], iodocyclocarbamates [19] and isoxazolines [20]. Although it has been reported that allylic amines can be synthesized by methods such as amination of allylic alcohols [21][22][23][24], direct allylic amination of simple alkenes [25][26][27], Morita–Baylis–Hillman reaction [28], alkenylation of imines [29][30][31][32
Efficient synthesis of β’-amino-α,β-unsaturated ketones
Beilstein J. Org. Chem. 2013, 9, 486–495, doi:10.3762/bjoc.9.52
- reaction of chiral imines with enolates derived from Weinreb amides [13][14]. In previous work on the asymmetric synthesis of 2,6-disubstituted piperidines by C–N bond formation, we demonstrated that intramolecular aza-Michael ”type” cyclisation [15] using a β'-carbamate-α,β-unsaturated ketone
Metal-mediated aminocatalysis provides mild conditions: Enantioselective Michael addition mediated by primary amino catalysts and alkali-metal ions
Beilstein J. Org. Chem. 2013, 9, 155–165, doi:10.3762/bjoc.9.18
- -metal salts of these betaine-like amides are able to form imines with enones, which are activated by Lewis acid interaction for nucleophilic attack by 4-hydroxycoumarin. The addition of 4-hydroxycoumarin to enones gives ee’s up to 83% and almost quantitative yields in many cases. This novel type of
- seems to be clear that the zwitterionic chelate shown in Figure 1 is too inert to form imines with carbonylic compounds. The choice of alkali metal does not affect the ee very markedly and the ee’s obtained in Table 1 are in the moderate range (up to 47%). In order to elucidate if Lewis acid free imines
A new family of four-ring bent-core nematic liquid crystals with highly polar transverse and end groups
Beilstein J. Org. Chem. 2013, 9, 26–35, doi:10.3762/bjoc.9.4
- unsubstituted benzylidene linkage was preferred due to the presence of the ortho-hydroxy group, which enhances the transverse dipole moment as well as the stability of the imines through intramolecular H-bonding to overcome the hydrolytic instability of the molecules towards moisture. The bent-core platform was
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