Optimization of enantiocontrol in cis-selective cyclopropanation reactions catalyzed by dirhodium(ii) tetrakis[alkyl 2-oxaazetidine-4(S)-carboxylates]

Doyle, Michael P.; Davies, Simon B.; Hu, Wenhao

doi:10.1039/b001464h

Cited by 48 publications

(39 citation statements)

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“…In general, chiral dirhodium(II) catalysts do not provide high enantioselectivities; there is a remarkable exception in chiral azetidine-4-carboxylate-ligated dirhodium(II) catalysts. 10 They produce enantioselectivities up to 76 and 52% ee, respectively, for 2a and 3a (Scheme 1). † Dirhodium(II) catalysts of general formula Rh 2 (O 2 CR) 2 (PC) 2 , containing two ortho-metalated aryl phosphines (PC) in a head to tail arrangement, 11 (Fig.…”

Section: Received (In Liverpoolmentioning

confidence: 99%

Enantiocontrol in the intermolecular cyclopropanation reaction catalyzed by dirhodium(ii) complexes with ortho-metalated aryl phosphine ligands

et al. 2001

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Section: Received (In Liverpoolmentioning

confidence: 99%

Enantiocontrol in the intermolecular cyclopropanation reaction catalyzed by dirhodium(ii) complexes with ortho-metalated aryl phosphine ligands

et al. 2001

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“…Dirhodium(II) Tetrakis[2-methyl-l-propyl 2-oxa-3,3-difluoroazetidine-4(R)-carboxylate] (6 a) Prepared and purified in 65% overall yield by standard methods; [11,13,14] [a] D 25 = +250.8 (c 0.43, MeCN); anal. found: C, 38.3; H, 4.1; N, 6.9, calcd.…”

Section: Methodsmentioning

confidence: 99%

“…1) 6 was less selective diastereoselectively and enantioselectively than its non-fluorinated counterparts (8). [14] 1 However, in ylide formation and [2,3]-sigmatropic rearrangement with allyl iodide and ethyl diazoacetate (Eq. 2), [15] a transformation that was only moderately successful (12±15% yield of 11, up to 39% ee) with other chiral dirhodium(II) carboxamidates, moderate yields and significantly higher % ee values were achieved for 11 with fluorinated catalysts 6 ( Table 1), and these results suggest that there may be further advantages for these catalysts in ylide transformations.…”

Section: Full Papermentioning

confidence: 99%

Reactivity Enhancement for Chiral Dirhodium(II) Tetrakis(Carboxamidates)

Doyle

Phillips

et al. 2001

Adv. Synth. Catal.

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Difluorinated ligands from azetidinone‐4‐carboxylates and pyrrolidinone‐5‐carboxylate have been prepared, substituted onto dirhodium(II), and the reactivities and selectivities of the resulting catalysts have been examined. The fluorinated catalysts exhibit enhanced reactivity towards diazo decomposition but diminished enantioselectivities for cyclopropanation. Selectivity for ylide formation and rearrangement or Si‐H insertion is enhanced or similar to that with unfluorinated analogues.

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“…Diastereoselectivity is modest; however, the chiral catalysts with carboxamidate ligands show a propensity to form the cis-isomer in preference to the thermodynamically favored trans-isomer (for example, Eq. 8) [43]. Using an azetidinone with a menthyl-carboxylate attachment 22, diastereoselectivities as high as 92:8 (cis/trans) were achieved in the synthesis of 23 [44].…”

Section: Intermolecular Reactionsmentioning

confidence: 97%

Chiral Dirhodium(II) Carboxamidates for Asymmetric Cyclopropanation and Carbon–Hydrogen Insertion Reactions

Doyle

2005

Modern Rhodium‐Catalyzed Organic Reactions

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In 1989-1990 three groups published initial results relating to the development of dirhodium(II) catalysts for asymmetric transformations of diazo compounds [1][2][3]. Two focused on amino acid carboxylate ligands [1,2], and one of them fortuitously found that prolinate ligands had unusual selectivity in reactions of diazoacetates and related substrates [2], even though the ligand's chiral centers lie far from the axial sites of dirhodium(II), which is where the carbene intermediate is formed. This discovery has led to very significant undertakings by Davies, particularly with aryl-and vinyldiazoacetates [4-8], but they have already been described in Chapter 14.On the basis of reports by Bear and co-workers [10-12] and the discovery that carboxamidate ligands could be introduced onto dirhodium(II) by semi-automated methods [13], Doyle and co-workers began their development of carboxamidate ligands for dirhodium with oxazolidinones (for example, 1 and 2), but with limited success in achieving high enantiocontrol [3]. Only when a carboxylate attachment, as in pyrrolidinone 3, rather than an isopropyl or benzyl group, as in 1 or 2, was placed in proximity to the reaction center, could high enantiocontrol be achieved [14]. The key developments here were: 1) the methodology for the semi-automated synthesis of dirhodium(II) carboxamidates by trapping acetic acid with sodium carbonate in a Soxhlet extraction apparatus (Eq. 1) [15]; and 2) the discovery of the high selectivity enhancement afforded by the carboxylate attachment [16]. Scheme 15.6 (cont.) Scheme 15.7 Synthesis of 2-deoxyxylolactone. 93 : 7

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Optimization of enantiocontrol in cis-selective cyclopropanation reactions catalyzed by dirhodium(ii) tetrakis[alkyl 2-oxaazetidine-4(S)-carboxylates]

Cited by 48 publications

References 12 publications

Enantiocontrol in the intermolecular cyclopropanation reaction catalyzed by dirhodium(ii) complexes with ortho-metalated aryl phosphine ligands

Enantiocontrol in the intermolecular cyclopropanation reaction catalyzed by dirhodium(ii) complexes with ortho-metalated aryl phosphine ligands

Reactivity Enhancement for Chiral Dirhodium(II) Tetrakis(Carboxamidates)

Chiral Dirhodium(II) Carboxamidates for Asymmetric Cyclopropanation and Carbon–Hydrogen Insertion Reactions

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