A Homo [3+2] Dipolar Cycloaddition: The Reaction of Nitrones with Cyclopropanes

Young, Ian S.; Kerr, Michael A.

doi:10.1002/ange.200351573

Cited by 109 publications

(43 citation statements)

References 28 publications

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“…This novel [3+3] cyclization of nitrones and allenes has no literature precedence, though a very recently described reaction between nitrones and electron-deficient cyclopropanes to provide tetrahydro-1,2-oxazines should be mentioned in this context. [24] Gratifyingly, additions of lithiated alkoxyallenes with nitrones are highly stereoselective, mostly giving synconfigured 1,2-oxazines under standard conditions, whereas anti compounds are produced in excess through precomplexation of the nitrones with diethylaluminium chloride. Since the received 1,2-oxazines can be transformed into a variety of cyclic and acyclic enantiopure compounds, the stereodivergent method described here is an excellent tool for efficient chain-elongations of carbohydrates.…”

Section: Discussionmentioning

confidence: 99%

Stereodivergent Syntheses of Highly Substituted Enantiopure 4‐Alkoxy‐3,6‐dihydro‐2H‐1,2‐oxazines by Addition of Lithiated Alkoxyallenes to Carbohydrate‐Derived Aldonitrones

et al. 2005

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Additions of lithiated alkoxyallenes to D-glyceraldehydebased nitrones 1 and 2 did not provide the expected hydroxylamine derivatives. Instead, a novel [3+3] cyclization process furnished 4-alkoxy-3,6-dihydro-2H-1,2-oxazines 9-14 with excellent syn selectivities and in moderate to good yields. Through precomplexation of the nitrones the corresponding anti-configured 1,2-oxazines 9, 10 and 13 could be obtained with high stereoselectivity. The reactions of nitrones 3-6, derived from D-erythrose or D-threose, generally proceeded less diastereoselectively, but reasonable yields of anti-configured 1,2-oxazines such as anti-17 and anti-19 could be obtained under Lewis acid promotion conditions. This was also the case for reactions of the D-arabinose-derived nitrone 7, which provided the anti-1,2-oxazines 23 and

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Section: Discussionmentioning

confidence: 99%

Stereodivergent Syntheses of Highly Substituted Enantiopure 4‐Alkoxy‐3,6‐dihydro‐2H‐1,2‐oxazines by Addition of Lithiated Alkoxyallenes to Carbohydrate‐Derived Aldonitrones

et al. 2005

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“…Lewis acid catalysis was demonstrated previously for the reaction of 1 a with nitrones [13] and imines, [14] as well as in related [3+2]…”

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confidence: 95%

Donor–Acceptor Cyclopropanes as Three‐Carbon Components in a [4+3] Cycloaddition Reaction with 1,3‐Diphenylisobenzofuran

et al. 2008

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“…[9] Among the methods developed for the preparation of such compounds, [10] the [3+3] cycloaddition of donor-acceptor cyclopropanes with nitrones, pioneered by Kerr and co-workers, [11] is a particularly elegant approach. They found that nitrones 3 react smoothly with cyclopropanes 2 in the presence of Yb(OTf) 3 ·x H 2 O to give the cis isomers 4 diastereospecifically (see Table 1).…”

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confidence: 99%

Highly Enantioselective and Diastereoselective Cycloaddition of Cyclopropanes with Nitrones and Its Application in the Kinetic Resolution of 2‐Substituted Cyclopropane‐1,1‐dicarboxylates

2007

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Trisoxazolines [1] have been applied widely in asymmetric catalysis [2] and molecular recognition. [3] In our efforts to develop superior catalysts that are cheap, readily accessible, air stable, and water tolerant, we designed and synthesized the pseudo-C 3 -symmetric trisoxazoline 1 b (Scheme 1) by the sidearm approach, and found that 1 b/Cu II promoted smoothly the highly enantioselective Friedel-Crafts reaction of indoles with arylidene malonates [4] and the Kinugasa reaction.[5] We also described tox/Co II -catalyzed [3+2] cycloaddition reactions between nitrones and alkylidene malonates in which the endo/exo selectivity could be controlled well by the reaction temperature. Thus, both cis and trans isoxazolidines could be prepared enantioselectively.[6] Herein, we report that the system tox/Ni II catalyzes the [3+3] cycloaddition of racemic 2-substituted cyclopropane-1,1-dicarboxylates with nitrones to provide ready access to optically active tetrahydro-1,2-oxazine derivatives with high diastereoselectivity and enantioselectivity. Furthermore, this reaction can be employed for the kinetic resolution [7] of 2-substituted cyclopropane-1,1-dicarboxylates to furnish these compounds in optically active form with excellent ee values.Tetrahydro-1,2-oxazine derivatives occur frequently in biologically active compounds [8] and are valuable synthetic intermediates.[9] Among the methods developed for the preparation of such compounds, [10] the [3+3] cycloaddition of donor-acceptor cyclopropanes with nitrones, pioneered by Kerr and co-workers, [11] is a particularly elegant approach. They found that nitrones 3 react smoothly with cyclopropanes 2 in the presence of Yb(OTf) 3 ·x H 2 O to give the cis isomers 4 diastereospecifically (see Table 1). Recently, Sibi et al. developed a highly efficient asymmetric version of this reaction. [12] They reported that nitrones react with cyclopropane-1,1-dicarboxylates to afford tetrahydro-1,2-oxazine derivatives with high enantioselectivity in the presence of dbfox/Ni II (10 mol %; dbfox = 4,6-dibenzofurandiyl-2,2-bisoxazoline). When 2-substituted cyclopropane-1,1-dicarboxylates were used as substrates, and the quantity of the catalyst was increased to 30 mol %, the reactions proceeded smoothly to give the products with high ee values but with low diastereoselectivities (the cis/trans ratio ranged from 1.0:1.4 to 1.0:0.8).Gratifyingly, we found that diethyl 2-phenylcyclopropane-1,1-dicarboxylate (2 a) reacted smoothly with nitrone 3 a to furnish the cycloaddition adduct in 99 % yield with excellent diastereoselectivity (d.r. > 99:1) in the presence of a catalytic amount of 1 b/Ni(ClO 4 ) 2 ·6 H 2 O. Further studies showed that ligands derived from iPr-box (box = bisoxazoline) influenced strongly both the enantioselectivity and diastereoselectivity of the reaction. The bisoxazoline 1 a without a pendant group gave the desired product with good diastereoselectivity (d.r. 97:3) but only 20 % ee (Table 1, entry 1). However, when a pyrid-2-yl or oxazolinyl group was introduced as a pend...

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A Homo [3+2] Dipolar Cycloaddition: The Reaction of Nitrones with Cyclopropanes

Cited by 109 publications

References 28 publications

Stereodivergent Syntheses of Highly Substituted Enantiopure 4‐Alkoxy‐3,6‐dihydro‐2H‐1,2‐oxazines by Addition of Lithiated Alkoxyallenes to Carbohydrate‐Derived Aldonitrones

Stereodivergent Syntheses of Highly Substituted Enantiopure 4‐Alkoxy‐3,6‐dihydro‐2H‐1,2‐oxazines by Addition of Lithiated Alkoxyallenes to Carbohydrate‐Derived Aldonitrones

Donor–Acceptor Cyclopropanes as Three‐Carbon Components in a [4+3] Cycloaddition Reaction with 1,3‐Diphenylisobenzofuran

Highly Enantioselective and Diastereoselective Cycloaddition of Cyclopropanes with Nitrones and Its Application in the Kinetic Resolution of 2‐Substituted Cyclopropane‐1,1‐dicarboxylates

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