Reaction Of Aldimines Research Articles

Divergent Synthesis of Multi-Substituted Aminotetralins via [4+2] Annulation of Aldimines with Alkenes by Rare-Earth-Catalyzed Benzylic C(sp3 )-H Activation.

The search for efficient and selective methods for the divergent synthesis of multi-substituted aminotetralins is of much interest and importance. We report herein for the first time the diastereoselective [4+2] annulation of 2-methyl aromatic aldimines with alkenes via benzylic C(sp3 )-H activation by half-sandwich rare-earth catalysts, which constitutes an efficient route for the divergent synthesis of both trans and cis diastereoisomers of multi-substituted 1-aminotetralin derivatives from readily accessible aldimines and alkenes. The use of a scandium catalyst bearing a sterically demanding cyclopentadienyl ligand such as C5 Me4 SiMe3 or C5 Me5 exclusively afforded the trans-selective annulation products in the reaction of aldimines with styrenes and aliphatic alkenes. In contrast, the analogous yttrium catalyst, whose metal ion size is larger than that of scandium, yielded the cis-selective annulation products. This protocol features 100 % atom-efficiency, excellent diastereoselectivity, broad substrate scope, and good functional group compatibility. The reaction mechanisms have been elucidated by kinetic isotope effect (KIE) experiments and the isolation and transformations of some key reaction intermediates.

Divergent Synthesis of Multi‐Substituted Aminotetralins via [4+2] Annulation of Aldimines with Alkenes by Rare‐Earth‐Catalyzed Benzylic C(sp3)−H Activation

AbstractThe search for efficient and selective methods for the divergent synthesis of multi‐substituted aminotetralins is of much interest and importance. We report herein for the first time the diastereoselective [4+2] annulation of 2‐methyl aromatic aldimines with alkenes via benzylic C(sp3)−H activation by half‐sandwich rare‐earth catalysts, which constitutes an efficient route for the divergent synthesis of both trans and cis diastereoisomers of multi‐substituted 1‐aminotetralin derivatives from readily accessible aldimines and alkenes. The use of a scandium catalyst bearing a sterically demanding cyclopentadienyl ligand such as C5Me4SiMe3 or C5Me5 exclusively afforded the trans‐selective annulation products in the reaction of aldimines with styrenes and aliphatic alkenes. In contrast, the analogous yttrium catalyst, whose metal ion size is larger than that of scandium, yielded the cis‐selective annulation products. This protocol features 100 % atom‐efficiency, excellent diastereoselectivity, broad substrate scope, and good functional group compatibility. The reaction mechanisms have been elucidated by kinetic isotope effect (KIE) experiments and the isolation and transformations of some key reaction intermediates.

Light-controlled pKa value of chiral Brønsted acid catalysts in enantioselective aza-Friedel-Crafts reaction.

Bis(dithienylethene)-based BINOL-derived phosphoric acid (DTE-BPA) has been developed as a light-controlled chiral organocatalyst for the first time. The photoinduced modulation of the reactivity and selectivity via the open/close isomerization of the DTE scaffold led to superior light-controlled ability in the enantioselective aza-Friedel-Crafts reaction of aldimines with indoles. DFT studies showed that photoisomerization is accompanied by a shift of 1.1 pKa units between the open and closed isomers.

Crystallization Does It All: An Alternative Strategy for Stereoselective Aza-Henry Reaction.

An efficient and experimentally straightforward method for the stereoselective synthesis of a variety of β-nitro-α-amino carboxylic acids via aza-Henry (nitro-Mannich) reaction of aldimines is disclosed, yielding either anti- or a rarely reported syn-configuration. The reaction operates directly on free glyoxylic acid and generates imine species in situ. Crystallization-controlled diastereoselectivity enables isolation of the target compounds in high enantio- and diastereomeric purities by a simple filtration.

Chiral VAPOL Imidodiphosphoric Acid-Catalyzed Asymmetric Vinylogous Mannich Reaction for the Synthesis of Butenolides

Chiral butenolides were synthesized by the enantioselective vinylogous Mannich reaction. Chiral (VAPOL)-type imidodiphosphoric acids are efficient catalysts for the asymmetric vinylogous Mannich (AVM) reaction of aldimines and trimethylsiloxyfuran in toluene. Under the optimized conditions, a series of butenolides were obtained with high yields (up to 98%) and enantioselectivities (up to 97% ee) as well as excellent diastereoselectivities (up to 99:1 dr).

Planar chiral [2.2]paracyclophane-based phosphine-phenol catalysts: application to the aza-Morita-Baylis-Hillman reaction of N-sulfonated imines with various vinyl ketones

Several planar chiral [2.2]paracyclophane-based phosphine-phenol catalysts were prepared and applied to the aza-Morita-Baylis-Hillman reaction of aldimines with vinyl ketones. The pseudo-ortho-substituted aryl[2.2]paracyclophanol, in which the phosphino group was located at the meta-position of the aryl group, showed an exceptionally high reactivity and good enantioselectivity for the reaction of N-tosylated aldimines with various alkyl or aryl vinyl ketones.

2-Halogenoimidazolium salt catalyzed aza-Diels-Alder reaction through halogen-bond formation.

2-Halogenoimidazolium salts are found to catalyze aza-Diels-Alder reaction of aldimines with Danishefsky diene in an efficient manner. Comparative studies and titration experiments support the formation of halogen bonding between imines and catalysts.

Reactivity of the Chiral Metallic Brønsted Acid [(η6-p-MeC6H4iPr)Ru(κ3P,O,O′-POH)][SbF6]2(POH= (SC1,RC2)-Ph2PC(Ph)HC(OH)HCH2OMe) toward Aldimines

Dichloromethane solutions of complex 1 catalyze both the aza-Diels–Alder (ADA) reaction of aldimines with cyclopentadiene and the aza-Friedel–Crafts (AFC) reaction between aldimines and indoles. Racemic adducts were obtained in both cases. NMR measurements of mixtures of the aldimine N-(4-methylbenzylidene)aniline (I) and 1, in a 20/1 molar ratio, reveal the formation of the deprotonated compound 2 and the corresponding iminium cation HI+ (H–N+). This cation is responsible for the achiral catalysis. Below 273 K, in 1/1 molar ratio mixtures of 1 and I, the chiral species 1·I (O–H···N) and 2·HI+ (O–···H–N+) were formed by intermolecular hydrogen bonding and proton transfer, respectively. The latter solutions catalyze stoichiometrically the ADA reaction between aldimine I and HCp with 16% ee. With 5 mol % of catalyst loading, a 6% ee can be obtained if the aldimine is slowly added to the solution (20 equiv in 60 h). Above 273 K, solutions containing 1 and aldimine I irreversibly evolve to the aniline complex...

Novel Diastereoselective Synthesis of trans-Fused Pyrrolo[3,4-b]quinolines Through Intramolecular Imino Diels–Alder Reaction

Synthesis of a series of 1aR,2S,4aS-hexahydropyrrolo[3,4-b]quinolines has been achieved by the intramolecular cyclization reaction of aldimines derived from aromatic amines and (S)-2-(N-(3-methylbut-2-enyl)-N-tosyamino)-3-methylpropanal/(S)-2-(N-(3-methylbut-2-enyl)-N-tosyamino)-3-phenylpropanal in acetonitrile with InCl3 as a catalyst, in excellent yields and in short duration of time, under mild conditions.

Mannich-Type Reactions of Aldimines and Hetero Diels-Alder Reactions of Aldehydes Catalyzed by Anion-Type Lewis Bases Derived from a Single Molecule

Mannich-type reactions of aldimines with silyl enolates and hetero Diels-Alder reactions of aldehydes with Danishef-sky’s diene in the presence of anion catalysts derived from proline were performed to afford the corresponding products in high yields.

Catalytic Asymmetric Vinylogous Mannich-type (AVM) Reaction of Nonactivated α-Angelica Lactone

A direct highly diastereo- and enantioselective asymmetric vinylogous Mannich-type (AVM) reaction of aldimines with nonactivated natural α-angelica lactone has been successfully developed. It was demonstrated that the nonactivated natural α-angelica lactone is a useful vinylogous nucleophile to give the chiral δ-amino γ,γ-disubstituted butenolide carbonyl derivatives. The N,N'-dioxide L2-Sc(III) complex is efficient toward the obtention of a range of corresponding products with adjacent quaternary and tertiary stereocenters in excellent dr and ee values.

ChemInform Abstract: Which Is the Actual Catalyst: Chiral Phosphoric Acid or Chiral Calcium Phosphate?

AbstractA highly enantioselective direct Mannich‐type reaction of aldimines with a broad range of 1,3‐dicarbonyl compounds with the use of a chiral phosphoric acid in the presence or absence of Ca(II) is demonstrated.

ChemInform Abstract: Catalytic, Enantioselective Synthesis of α-Aminonitriles with a Novel Zirconium Catalyst.

Strecker reactions of aldimines with Bu3 SnCN in the presence of the novel chiral zirconium binuclear catalyst 1 provide α-aminonitriles in good yields and with high enantioselectivities. The reaction can be applied to a wide range of substrates. Since both enantiomers of the chiral sources are readily avaibable, both enantiomers of the α-aminonitriles are easily prepared according to this method. L=N-methylimidazole.

ChemInform Abstract: Chiral Catalyst Optimization Using Both Solid-Phase and Liquid-Phase Methods in Asymmetric Aza Diels-Alder Reactions.

[formula: see text] In the presence of 1-5 mol % of a chiral zirconium catalyst, aza Diels-Alder reactions of aldimines with Danishefsky's dienes proceeded smoothly to afford the corresponding piperidine derivatives in high yields with high enantioselectivities. For the catalyst optimization, solid-phase and liquid-phase methods were successfully used. In the solid-phase approach, polymer-supported (R)-1,1'-binaphthols (BINOLs) have been synthesized and rapid optimization using the solid-phase reactions has been achieved. On the other hand, novel chiral zirconium cyanides were developed as excellent catalysts using the liquid-phase approach.

Preparation of Unsaturated Aminonitriles from the Aza-Morita-Baylis-Hillman Reactions of Aldimines with Penta-2,4-dienenitrile

N-(Phenylsulfonyl)aldimines undergo facile aza-Morita-Baylis-Hillman reactions with penta-2,4-dienenitrile in anhydrous DMF in the presence of catalytic 3-hydroxyquinuclidine and methanol to afford the corresponding unsaturated aminonitriles.

Synthesis of New Bis‐imidazole Derivatives

AbstractThe reaction of aldimines with α‐(hydroxyimino) ketones of type 10 (1,2‐diketone monooximes) was used to prepare 2‐unsubstituted imidazole 3‐oxides 11 bearing an alkanol chain at N(1) (Scheme 2, Table 1). These products were transformed into the corresponding 2H‐imidazol‐2‐ones 13 and 2H‐imidazole‐2‐thiones 14 by treatment with Ac2O and 2,2,4,4‐tetramethylcyclobutane‐1,3‐dithione, respectively (Scheme 3). The three‐component reaction of 10, formaldehyde, and an alkane‐1,ω‐diamine 15 gave the bis[1H‐imidazole 3‐oxides] 16 (Scheme 4, Table 2). With Ac2O, 2,2,4,4‐tetramethylcyclobutane‐1,3‐dithione or Raney‐Ni, the latter reacted to give the corresponding bis[2H‐imidazol‐2‐ones] 19 and 20, bis[2H‐imidazol‐2‐thione] 21, and bis[imidazole] 22, respectively (Schemes 5 and 6). The structures of 11a and 16b were established by X‐ray crystallography.

Indium Trichloride Catalyzed One‐Pot Synthesis of Indolo[2,1‐a]pyrrolo[4′,3′:2,3]‐7a,8,13,13b‐tetrahydroquinolines Through Intramolecular Imino Diels—Alder Reactions.

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Aza‐Morita—Baylis—Hillman Reactions and Cyclizations of Conjugated Dienes Activated by Sulfone, Ester, and Keto Groups.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF.

Rhenium‐Catalyzed Addition of Trimethylsilylacetylene to Aldimines.

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Synthesis of 3,3‐Difluoroazetidines.

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