Simple Generation of Ester-Stabilized Azomethine Ylides from 2-Amino Esters and Carbonyl Compounds. Stereochemistry of Their Cycloadditions

Tsuge, Otohiko; Kanemasa, Shuji; Oh‐e, Masahito; Yorozu, Kiyotaka; Takenaka, Shigeori; Ueno, Keiji

doi:10.1246/bcsj.60.4067

Cited by 53 publications

(12 citation statements)

References 18 publications

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“…Reaction of 45 with dimethylfumarate, an activated dipolarophile, gave 3,4-di(methoxycarbonyl)-2-ethoxycarbonyl-Nphenylpyrrolidine in 87% yield as a mixture of 2 diastereoisomers on C 2 in a ratio of 2 : 1. 28 Reaction of 45 with racemic 5-methoxy-2(5H)-furanone 2 yielded N-phenyl-1-oxa-2-oxo-3-methoxycarbonyl-4-aza-6-methoxy-[3.3.0]bicyclooctane and N-phenyl-1-oxa-2-oxo-5-methoxycarbonyl-4-aza-6-methoxy-[3.3.0]bicyclooctane in 55% yield as a mixture of 8 isomers.…”

Section: Scheme 12mentioning

confidence: 99%

Asymmetric 1,3-dipolar cycloadditions to 5-(R)-menthyloxy-2(5H)-furanone

Rispens¹,

Keller

Lange

et al. 1994

Tetrahedron: Asymmetry

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Abstract:Various diazo compounds, nitrile oxides, nitrones and azomethine ylides were examined in 1,3-dipolar cycloadditions to enantiomerically pure 5-(R)-menthyloxy-2(5H)-furanone 1a. Pyrazoline 9 was obtained in 100% c.y. as a mixture of 2 diastereoisomers in ratios up to 72 : 28, whereas pyrazoline 16 was obtained in 100 % c.y. as a single enantiomer. Photochemically pyrazolines 9 and 10 have been converted to cyclopropanes 11 and 13. Under thermal conditions pyrazoline 9 is converted to 4-methyl-5-menthyloxy-2(5H)-furanone. Isoxazoles 21a-24a were obtained enantiomerically pure via nitrile oxide addition to 1a in 64-67% yield. Nitrone addition afforded isoxazolidines 27, 28 and 34 with complete anti-facial-and regiochemistry, but with endo-exo selectivities up to 76%. Enantiomerically pure isoxazolidines were obtained in 25-75% yield. Pyrrolidine 36 was obtained diastereomerically pure in 81% c.y. Pyrrolidines 42 and 45, however, were obtained as diastereomeric mixtures in 37% resp. 6% yield. IntroductionCycloadditions are undoubtedly a cornerstone in synthetic methodology. In order to control the absolute stereochemistry of the ring systems which are formed, regio-, facial-, and endo/exo-selectivity are decisive factors. Therefore it is not surprising that a variety of asymmetric Diels-Alder reactions and 1,3-dipolar cycloadditions have been developed in the last decade.1,2 The 1,3-dipolar cycloaddition reactions of nitrones and nitrile oxides to alkenes have been extensively used for the preparation of isoxazolidines and isoxazoles.3 Further transformations offer access to a variety of functional intermediates for synthesis, in many cases with multiple stereogenic centers introduced during the cycloaddition

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Section: Scheme 12mentioning

confidence: 99%

Asymmetric 1,3-dipolar cycloadditions to 5-(R)-menthyloxy-2(5H)-furanone

Rispens¹,

Keller

Lange

et al. 1994

Tetrahedron: Asymmetry

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Section: Short Communicationsmentioning

confidence: 88%

“…The products structure was confirmed by their IR, 1 H and 13 C NMR, and mass spectra. The formation of only one possible regioisomer followed from the 1 H and 13 C NMR data, as well as from comparison of the spectral data with those reported in [6,7]. The 1 H and 13 C NMR spectra were recorded on a Bruker DRX 500 spectrometer at 500.13 and 126 MHz, respectively, using DMSO-d 6 as solvent and tetramethylsilane as internal reference; the 13 C NMR spectra were obtained with complete decoupling from protons.…”

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confidence: 99%

L-proline-catalyzed 1,3-dipolar cycloaddition of some Schiff bases to methyl 4-[1-oxo-2-(2-oxo-2,3-dihydro-1H-indol-3-ylidene)ethyl]phenylcarbamate

et al. 2011

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SHORT COMMUNICATIONS[3 + 2]-Cycloaddition is an efficient method of synthesis of five-membered nitrogen-containing heterocycles, including proline derivatives which exhibit a broad spectrum of biological activity [1,2]. Synthetic precursors of proline derivatives may be Schiff bases that are readily available from aldehydes and α-amino acid esters. The use of Brønsted acids as catalysts in 1,3-dipolar cycloaddition of azomethine ylides to unsymmetrical electron-deficient alkenes was studied to a lesser extent [3] than catalysis by Lewis acids. In these transformations, N-methylmaleimide [4], N-phenylmaleimide, dimethyl maleate, and dimethyl fumarate [3] were used as dipolarophiles.The present communication reports on 1,3-dipolar cycloaddition of Schiff bases derived from ethyl (benzylideneamino)acetate (IIa) and methyl 2-(benzylideneamino)propanoate (IIb) to methyl 4-[1-oxo-2-(2-oxo-2,3-dihydro-1H-indol-3-ylidene)ethyl]phenylcarbamate (I) in the presence of L-proline (20 mol %). It is well known that L-proline (a cyclic α-amino acid) effectively catalyzes reactions involving iminium and enamine intermediates and that it is an efficient organocatalyst in various processes [5]. In our case, the acidity of amino acid and its association with 1,3-dipole are important factors. Reaction of α-amino acid with Schiff base generates azomethine ylide as a result of protonation of the imino nitrogen atom and deprotonation of the α-carbon atom. Electrostatic and other interactions of the conjugate base of enantiomerically pure Brønsted acid with azomethine ylide could give rise to asymmetric induction in the subsequent 1,3-dipolar cycloaddition.We found that azomethine ylides generated from Schiff bases IIa and IIb did not react with methyl 4-[1-oxo-2-(2-oxo-2,3-dihydro-1H-indol-3-ylidene)-ethyl]phenylcarbamate (I) in methylene chloride at room temperature over a period of 5 days. On the other hand, heating of the reactants in boiling toluene (reaction time 8 h) gave the corresponding racemic spiro compounds IIIa and IIIb possessing a pyrrolidine ring. The products structure was confirmed by their IR, 1 H and 13 C NMR, and mass spectra. The formation of only one possible regioisomer followed from the 1 H and 13 C NMR data, as well as from comparison of the spectral data with those reported in [6,7]. Ethyl 4′-[4-(methoxycarbonylamino)benzoyl]-2′phenyl-2-oxo-1,2-dihydrospiro[indole-3,3′-pyrroli-R = H, R′ = Et (a); R = R′ = Me (b).

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“…iminium salts 2 are stereospecifically converted into both unsaturated aldehydes/ketones 6 with a (Z)-CϪC double Scheme 1 Typical methods used for the preparation of the synthetically very useful unsaturated carbonyl compounds include the base-induced fragmentation of monotosylated 1,3-diols [1] [2] [3] [4] [5] [6] , flash thermolysis of γ-hydroxyammonium compounds [7] and the selective CϪC bond cleavage of quaternized β-amino aldehydes and β-amino ketones [8] . In most cases, the generated CϪC double bond is an exomethylene group.…”

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confidence: 99%

“…In the course of our previous research on bond cleavage reactions of 1-azaadamantane derivatives, quaternized β-The reduction of 3 was carried out with NaBH 4 and yielded the amino alcohols 4 (R ϭ H) [18] [19] . The addition amino ketones and β-amino aldehydes, NaH in THF was found to be very effective for inducing fragmentation reacof Grignard reagents gave 4 (R ϭ Me, Et, Bzl, Ph and naphthyl) [20] [21] [22] .…”

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confidence: 99%