An Easy Synthesis of Aliphatic and Aromatic N-Sulfonyl Aldimines

Chemla, Fabrice; Hebbe, Virginie; Normant, Jean F.

doi:10.1055/s-2000-6232

Cited by 163 publications

(128 citation statements)

References 8 publications

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“…To a solution of imine 3a [14] (0.1 mmol, 26.0 mg) and catalyst 1 [6] (0.02 mmol, 6.2 mg) in THF (1.0 mL) was added malonic acid half thioester 2a [15] (0.2 mmol, 39.2 mg). The reaction mixture was stirred at the temperature and the time stated, without any precaution of excluding moisture or air, after which 4a was obtained through purification of the reaction mixture by chromatography on silica gel (EtOAc/n-hexane, 1:8) as a white solid; yield: 33.0 mg (83 %); mp 117 8C; …”

Section: Experimental Section (S)-s-phenyl 3-phenyl-3-(tosylamino)promentioning

confidence: 99%

Organocatalytic Enantioselective Decarboxylative Addition of Malonic Half Thioesters to Imines

Ricci,

Pettersen,

Bernardi

et al. 2007

Adv Synth Catal

121

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We describe a biomimetic organocatalytic enantioselective decarboxylative addition of malonic acid half thioesters to imines. This simple protocol makes use of readily available Cinchona-derived organocatalysts and nucleophiles at the carboxylate oxidation state. The resulting b-amino thioesters, being attractive precursors for the preparation of optically active b-amino acids, are formed in good yields and in up to 79 % ee. As suggested by several mechanistic insights the desired products are formed via initial formation of a thioester acetate enolate via decarboxylation of the malonic acid half thioester, followed by addition to the imine.Keywords: b-amino acids; asymmetric catalysis; imines; Mannich reaction; organic catalysis Recently, the metal-assisted direct aldol reaction, that is, the in situ formation of enolates and their involvement into a catalytic process, has gained sustained interest.[1a] The majority of this research focuses on the use of specific reactive ketone-or aldehyde-based nucleophiles. As a consequence, subsequent oxidation of the a-functionalized carbonyl compounds is required in order to obtain a-functionalized carboxylate compounds. Therefore it is desirable to develop processes using nucleophiles at the carboxylate oxidation state and as a result of this demand a few examples employing metal-based catalysts or promoters based on such system have been reported.[1b-g] However, the catalytic generation of an ester enolate is not a trivial task, due to the high pK a value of the a-protons in the parent compound.[2] Inspired by naturally occurring enzymatic polyketide biosynthesis, proceeding through the decarboxylative generation of thioester enolates, Shair and co-workers used malonic acid half thioesters as thioester enolate intermediates in a copper-catalyzed decarboxylative aldol reaction. [3] Indeed, these thioesters are very attractive candidates for the generation of an ester enolate equivalent under very mild reaction conditions, due to the intrinsic driving force connected with the loss of CO 2 , and the stabilizing effect of the sulfur moiety on the resulting enolate. [3] In order to avoid the use of metal salts as catalysts in this biomimetic process, an organocatalytic approach would be highly attractive. To the best of our knowledge there are no reports describing the use of chiral organocatalysts in such systems. Herein we would like to present a straightforward organocatalytic enantioselective decarboxylative addition of malonic acid half thioesters to imines (Mannich reaction) resulting in optically active bamino thioesters which are obvious precursors of important b-amino acids. [4] At the outset of this study initial attempts were performed using simple achiral organic bases as catalysts and we were pleased to find that the reaction could be catalyzed by simple organic bases such as DABCO, imidazole and DBU. For example, the reaction of malonic acid half thioester 2a with N-Ts imine 3a in toluene in the presence of 20 mol % DABCO led to good conversion (80 %) ...

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Section: Experimental Section (S)-s-phenyl 3-phenyl-3-(tosylamino)promentioning

confidence: 99%

Organocatalytic Enantioselective Decarboxylative Addition of Malonic Half Thioesters to Imines

Ricci,

Pettersen,

Bernardi

et al. 2007

Adv Synth Catal

121

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“…This chemistry was applied unsuccessfully toward the synthesis of enolizable N-sulfonyl aldimines and unfortunately this method shares a common limitation with several other methods of N-tosylaldimine synthesis 18,33,34,36,37 in that it does not appear to be applicable to the synthesis of N-sulfonyl aldimines derived from aldol condensations being obtained instead. We have also studied the reaction of sulfonamide with ketones.…”

Section: Resultsmentioning

confidence: 99%

A novel method for the synthesis of N-sulfonyl aldimines using AlCl3 under solvent-free conditions (SFC)

Sharghi¹,

Hosseini‐Sarvari²,

Ebrahimpourmoghaddam³

2007

Arkivoc

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“…[7][8][9][10][11][12][13][14][15][16][17] Various practical and simple synthesis of N-tosyl imines are known. [18][19][20][21][22][23][24][25][26] The toluenesulfonyl activating group of imine can be removed easily by treatment with Mg/MeOH, 27,28 treatment with phenol in refluxing HBr/HOAc solution with addition of H 2 O, 29 or treatment with SmI 2 in THF at room temperature. 30 Our group found that the Ln(O i Pr) 3 was a very effective catalyst for the aza-Henry reaction when the N-tosyl imine was used as the substrate (cat., 5 mol %; yield, 99%).…”

Section: Introductionmentioning

confidence: 99%

Asymmetric aza‐Henry reaction of N‐tosyl imine

et al. 2006

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An Easy Synthesis of Aliphatic and Aromatic N-Sulfonyl Aldimines

Abstract: N-Arenesulfonyl aldimines were prepared from aliphatic and aromatic aldehydes in a two-step transformation.

Cited by 163 publications

References 8 publications

Organocatalytic Enantioselective Decarboxylative Addition of Malonic Half Thioesters to Imines

Organocatalytic Enantioselective Decarboxylative Addition of Malonic Half Thioesters to Imines

A novel method for the synthesis of N-sulfonyl aldimines using AlCl3 under solvent-free conditions (SFC)

Asymmetric aza‐Henry reaction of N‐tosyl imine

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