Rigid backbone 1,8-anthracene-linked bis-oxazolines (AnBOXes): design, synthesis, application and characteristics in catalytic asymmetric aziridination

Ma, Lei; Jiao, Peng; Zhang, Qihan; Xu, Jiaxi

doi:10.1016/j.tetasy.2005.09.025

Cited by 53 publications

(31 citation statements)

References 49 publications

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“…1,3-disubstituted propenes are important skeletons found in natural products [40][41][42][43]. These compounds are also useful for a variety of synthetic transformations [44][45][46][47][48][49].…”

Section: Resultsmentioning

confidence: 99%

Palladium-catalyzed cross-couplings of allylic carbonates with triarylbismuths as multi-coupling atom-efficient organometallic nucleophiles

Rao

Banerjee

Giri

2010

Journal of Organometallic Chemistry

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Section: Resultsmentioning

confidence: 99%

Palladium-catalyzed cross-couplings of allylic carbonates with triarylbismuths as multi-coupling atom-efficient organometallic nucleophiles

Rao

Banerjee

Giri

2010

Journal of Organometallic Chemistry

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“…3,4 However, alkene aziridination, particularly asymmetric aziridination, is far less well developed than the closely related epoxidation. [5][6][7][8] We were attracted by the report of Xu in 2002 that enones can be aziridinated by hydrazinium salt 1 in the presence of NaH (Scheme 1). 9 By analogy with an earlier study, 10 this chemistry was assumed to proceed by deprotonation of 1 to give an N-N ylid (aminimine), which then undergoes Michael addition to the enone followed by ring closure to give the aziridine.…”

mentioning

confidence: 99%

N-Amino-N-methylmorpholinium Salts: Highly Active Aziridination Reagents for Chalcones

Armstrong¹,

Carbery²,

Lamont³

et al. 2006

Synlett

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A highly effective aziridination reagent, based on Nmethylmorpholine, is reported which effects rapid conversion of chalcones to N-unfunctionalised aziridines at room temperature.Aziridines are highly attractive synthetic intermediates, 2 largely because they can undergo ring opening with a variety of nucleophiles to give functionalised amine products. 3,4 However, alkene aziridination, particularly asymmetric aziridination, is far less well developed than the closely related epoxidation. 5-8 We were attracted by the report of Xu in 2002 that enones can be aziridinated by hydrazinium salt 1 in the presence of NaH (Scheme 1). 9 By analogy with an earlier study, 10 this chemistry was assumed to proceed by deprotonation of 1 to give an N-N ylid (aminimine), which then undergoes Michael addition to the enone followed by ring closure to give the aziridine. An advantage of the method is that it affords N-unsubstituted aziridines which allows flexibility in further functionalising the nitrogen with a choice of activating group. We reasoned that this process had potential for asymmetric aziridination if chiral hydrazinium salts were employed. However, the strong base and carcinogenic solvent employed in this work were unattractive, as were the relatively long reaction times. Therefore, we undertook a study of alternative reaction conditions and report here the discovery of two new base systems as well as a more reactive hydrazinium salt that is particularly convenient to prepare. Scheme 1We began by testing the Xu nitrate salt 1 (2 equiv) for aziridination of chalcone with alternative bases and solvents. Early studies showed that it was possible to use NaOH in MeCN, but the yield of aziridine was low (17% after 18 h). Therefore we prepared alternative hydrazinium nitrate salts by amination of several cyclic amines. While the hydrazinium salts derived from N-methylpyrrolidine and N-methylpiperidine gave comparable or lower yields of aziridine, we were delighted to find that the N-methylmorpholinium nitrate salt 2a (Scheme 2), prepared by amination of N-methylmorpholine (Scheme 2), effected aziridination of chalcone in 95% yield after only three hours under the NaOH/MeCN conditions (Scheme 3). While this result was encouraging, particularly in identifying the reactivity of the morpholine framework, we felt that the procedure used to prepare the hydrazinium nitrate salt 2a from N-methylmorpholine was inconvenient since it required reaction with hydroxylamine-O-sulfonic acid (HOSA) and Ba(NO 3 ) 2 over extended time periods at raised temperatures. Therefore, we were pleased to find that the corresponding iodide salt could be more readily prepared simply by treatment of commercially available N-aminomorpholine 3 with one equivalent of iodomethane in THF at 0°C. The hydrazinium iodide salt 2b was isolated after filtration as a white solid in 77% yield and can be further purified by recrystallisation from EtOH. Under the same NaOH/MeCN conditions, the iodide 2b afforded a slightly lower yield of aziridine than nitrate 2a (Schem...

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“…These results indicate that the ligand L1-Cu(OAc) 2 ÁH 2 O complexes can catalyze the enantioselective chlorination of 2-carboxylate indanones, and the enantioselectivity is affected by the structure of substrate. After analyzing the results in Table 4, it reveals that there may exist p-p stacking interaction between the C = O of NCS and the benzo ring of substrates, which stabilize the transition state in the asymmetric catalysis [47][48][49].…”

Section: Resultsmentioning

confidence: 99%

Enantioselective chlorination of β-keto esters and amides catalyzed by chiral copper(II) complexes of squaramide-linked bisoxazoline ligand

Jia

2014

Chinese Chemical Letters

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Rigid backbone 1,8-anthracene-linked bis-oxazolines (AnBOXes): design, synthesis, application and characteristics in catalytic asymmetric aziridination

Cited by 53 publications

References 49 publications

Palladium-catalyzed cross-couplings of allylic carbonates with triarylbismuths as multi-coupling atom-efficient organometallic nucleophiles

Palladium-catalyzed cross-couplings of allylic carbonates with triarylbismuths as multi-coupling atom-efficient organometallic nucleophiles

N-Amino-N-methylmorpholinium Salts: Highly Active Aziridination Reagents for Chalcones

Enantioselective chlorination of β-keto esters and amides catalyzed by chiral copper(II) complexes of squaramide-linked bisoxazoline ligand

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