Synthese homochiraler 3‐Oxa‐2,7‐diazabicyclo[3.3.0]octane aus Aminosäuren durch intramolekulare 1,3‐dipolare Cycloaddition von Nitronen

Aurich, Hans Günter; Frenzen, G.; Gentes, Christian

doi:10.1002/cber.19931260333

Cited by 36 publications

(13 citation statements)

References 23 publications

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“…11, 35,36 Olefin bearing O-tert-butyldimethylsilyl oximes, under the influence of BF 3 $OEt 2 , also react efficiently to generate N-unsubstituted bicycles. 37,38 Stirring a solution of 2-bromoacetophenone 9 and N-methyl allylamine in DCM for 10 min furnished the desired tertiary amine 5(III) a in quantitative yield, the already known 5(III)b required longer to reach the same extent of conversion (30 h).…”

Section: Resultsmentioning

confidence: 99%

An investigation of structure-reactivity relationships of δ-alkenyl oximes; competitive thermal reactions leading to cyclic nitrones and/or N-unsubstituted bicyclic isoxazolidines

Doyle

Heaney

2010

Tetrahedron

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a b s t r a c tThermal reactions of C-aryl d-alkenyl oximes give N-unsubstituted bicylic lactone, lactam and pyrrolidine fused isoxazolidines by an intramolecular oxime olefin cycloaddition pathway (IOOC) and/or cyclic nitrones by an azaprotio cyclotransfer (APT) route; a number of factors, including the nature of the aryl group, the oxime geometry and the structure of the linker between the oxime and the terminal alkene, contribute to the competition.

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Section: Resultsmentioning

confidence: 99%

An investigation of structure-reactivity relationships of δ-alkenyl oximes; competitive thermal reactions leading to cyclic nitrones and/or N-unsubstituted bicyclic isoxazolidines

Doyle

Heaney

2010

Tetrahedron

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“…[3][4][5]12 However, while diastereoselectively pure cycloadducts exo-2 could be obtained when the R substituent was sufficiently bulky (Scheme 1), 3,4 on the other hand the acetoxy group at the carbon C 3 of the N-methylnitrone 10a appeared unsuited to induce any diastereoselectivity. In fact, calculations of the transition-state energies by semiempirical methods 13 The diastereomeric isoxazolidines exo-11a 14 and endo12a 15 were readily separable by flash chromatography on silica gel.…”

Section: Methodsmentioning

confidence: 99%

Spirocyclopropane Isoxazolidines, Octahydropyrindin-4-ones and β-Lactams with Biomimetic Ethylene Release from the Electrophilic Substitution of a 1,1-Ethyleneallylzinc Complex

Paschetta¹,

Cordero²,

Paugam³

et al. 2001

Synlett

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Electrophilic substitution of 1-ethenylcyclopropyl mesylate by 3,3-diethoxypropanal in the presence of palladium(0) (5%) and diethylzinc (2 equivalents) provided 5-cyclopropylidene-1,1-diethoxy-3-hydroxypentane; its nitrone derivatives underwent intramolecular cycloaddition to provide spirocyclopropane isoxazolidines, which then were transformed under thermal or acidic conditions, into octahydropyrindin-4-ones or bicyclic b-lactams with the ethylene phytohormone extrusion, respectively. Use of chiral auxiliaries, i.e, (L)-2-acetoxylactate can lead to enantiomerically enriched heterocycles.It is a matter of common knowledge now, that the cyclopropane ring, which can selectively undergo either ring opening, or ring enlargement or cycloaddition reactions, provides building blocks of unprecedented synthetic potential. 1 It is also known that, when substituted by simple functionalities, natural or synthetic three-membered rings are endowed with a large spectrum of biological activities, allowing consequently the design of new drugs. 2 We have recently reported the ready asymmetric synthesis of cis-fused tricyclic isoxazolidines exo-2 involving regioselective nucleophilic substitution of p-1,1-ethyleneallylpalladium complex 1 by optically active a-amino acids, followed by diastereoselective 1,3-dipolar cycloaddition of the derived nitrones. Subsequently, the spirocyclopropane isoxazolidines exo-2 have been shown to undergo either thermally induced ring expansion into the pyrrolo[3,4-b]pyridin-4-ones 3, 3-5 or acid induced ring contraction into the b-lactams 4 with concomitant extrusion of ethylene (Scheme 1). 6In order to widen the scope of this new approach towards these biologically important compounds, we have now investigated an alternative access to spirocyclopropane isoxazolidines such as 2 based on the electrophilic substitution of 1,1-ethyleneallylzinc complexes.We have observed that, in the presence of diethylzinc in THF, the p-1,1-ethyleneallylpalladium complex 1, arising from the readily available 1-ethenylcyclopropylsulfonates 5a,b and palladium(0), 7,8,10 underwent through the formation of s-or p-1,1-dimethyleneallylzinc complexes 6, chemo-and regioselective electrophilic addition of aldehydes and ketones. 9 Effectively, substitution of mesylate 5a by 3,3-diethoxypropionaldehyde 7 11 performed in the presence of 5% of palladium(0) [from Pd(OAc) 2 and 2 PPh 3 ] and two equivalents of diethylzinc in THF at room temperature for 3 h, provided 5-cyclopropylidene-1,1-diethoxy-3-hydroxypentane 8, in 63% yield after chromatography (Scheme 2). Scheme 2O-protection (Ac 2 O, DMAP) of the secondary allylic alcohol 8 and subsequent deacetalisation under acidic conditions (0.2 M H 2 SO 4 , THF) led to the 3-acetoxy-5-cyclopropylidenepentanal 9a (R = Ac) in 72% overall yield. This aldehyde reacted at room temperature with N-methylhydroxylamine hydrochloride in the presence of one equivalent of pyridine in diethyl ether at 0°C to give the corresponding N-methylnitrone 10a which, spontaneously, evolved to a 1:1 mixture of ...

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“…[8] Then, the hydroxy group of ester 1c was protected as the TBS ether 1d (98%). [9] The prolinol derivatives 2a [10] and 2b were obtained from ester 1a after DIBALH reduction [11] and the consecutive protection of the newly formed OH group under standard conditions (98 -99% yield). The substitution pattern is detailed in Table 1 (Scheme 2).…”

Section: Auxiliary Controlled Aza-claisen Rearrangementsmentioning

confidence: 99%

“….08 mmol; prepared and characterized as reported [10] ), imidazole (1 g, 14.7 mmol) and DMAP (10 mg) in anhydrous THF (50 mL) were treated with TPSCl (2.9 g, 10.5 mmol) at 0 8C. After 3 hours of stirring at 20 8C (TLC control), the mixture was quenched with H 2 O (20 mL).…”

Section: Full Papersmentioning

confidence: 99%

Synthesis and Derivatization of Substituted (R)‐ and (S)‐ C‐Allylglycines

Zhang¹,

Münch²,

Nubbemeyer³

2004

Adv Synth Catal

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Various (R)-and (S)-C-allylglycine derivatives were synthesized by means of an auxiliary controlled diastereoselective aza-Claisen rearrangement. Starting from (S)-configured auxiliaries derived from optically active proline, an aza-Claisen rearrangement enabled us to synthesize a(R)-configured g,d-unsaturated amides. Since (R)-allylglycine derivatives could be directly generated by reacting N-allylproline derivatives and various protected glycine fluorides, the corresponding (S)-enantiomers were built-up via an initial a-chloroacetyl chloride rearrangement and a subsequent chloride azide substitution with complete inversion of the configuration.High diastereoselectivities were obtained ( > 15 : 1). The auxiliary could be efficiently removed by organolithium reactions of the amides furnishing a-amino ketones. Another allyllithium addition allowed us to introduce a second allyl chain with high diastereoselectivity. Final ring closures by means of metatheses using Grubbs (I) catalyst gave raise to the formation of enantiopure phenanthridines and cyclohexenes displaying defined substitution patterns ready for alkaloid total syntheses.

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Synthese homochiraler 3‐Oxa‐2,7‐diazabicyclo[3.3.0]octane aus Aminosäuren durch intramolekulare 1,3‐dipolare Cycloaddition von Nitronen

Cited by 36 publications

References 23 publications

An investigation of structure-reactivity relationships of δ-alkenyl oximes; competitive thermal reactions leading to cyclic nitrones and/or N-unsubstituted bicyclic isoxazolidines

An investigation of structure-reactivity relationships of δ-alkenyl oximes; competitive thermal reactions leading to cyclic nitrones and/or N-unsubstituted bicyclic isoxazolidines

Spirocyclopropane Isoxazolidines, Octahydropyrindin-4-ones and β-Lactams with Biomimetic Ethylene Release from the Electrophilic Substitution of a 1,1-Ethyleneallylzinc Complex

Synthesis and Derivatization of Substituted (R)‐ and (S)‐ C‐Allylglycines

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