Catalytic asymmetric induction in enantioselective conjugate addition of dialkylzincs to enones

Soai, Kenso; Yokoyama, S.; Hayasaka, Tomoiki; Ebihara, Katsumi

doi:10.1021/jo00252a063

Cited by 78 publications

(11 citation statements)

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“…Additionally, alkyl-substituted phosphine ligands MePPh 2 (40 % yield, 66 % ee; Table 1, entry 11) and PCy 3 (60 % yield, 50 % ee; Table 1, entry 12) only gave 2 a with modest yields and selectivity. Moreover, conjugate additions require the stoichiometric use of metal organic reagents (that is, Grignard, [25] as well as organotin, [26] zinc, [27] aluminium, [28] lithium, [29] and copper [30] species), or metalloid reagents (that is, organoboron, [31] and organosilicon [32] ), the preparation of which may be cumbersome and produce waste. As a control, the use of (S)-L3, which lacks the olefin donor, had a negative impact on the reaction performance (33 % yield, 64 % ee; Table 1, entry 17) in combination with (S)-L3 failed to improve the process.…”

Section: Thomas J Hoffman and Erick M Carreira*mentioning

confidence: 99%

“…However, alkyl-substituted cyclopentanones, other than those incorporating the most rudimentary of substituents, are not always easily accessed. Moreover, conjugate additions require the stoichiometric use of metal organic reagents (that is, Grignard, [25] as well as organotin, [26] zinc, [27] aluminium, [28] lithium, [29] and copper [30] species), or metalloid reagents (that is, organoboron, [31] and organosilicon [32] ), the preparation of which may be cumbersome and produce waste. By contrast, hydroacylations may be considered ideal [33] in so far as all of the atoms of the starting material are found in the product.…”

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confidence: 99%

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Catalytic Asymmetric Intramolecular Hydroacylation with Rhodium/Phosphoramidite–Alkene Ligand Complexes

Hoffman

Carreira

2011

Angewandte Chemie

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The rational design and development of novel transitionmetal catalysts bearing diolefin [1,2] and phosphine-olefin ligands [3] has recently gained attention for the promotion of catalytic enantioselective reactions such as conjugate and imine additions, as well as the cyclization of ynals. [4] The heteroleptic complexes generated from phosphine-alkene ligands can be particularly useful as they include at least two donors with distinct steric and electronic properties. Phosphine-alkene ligands featuring dibenzo[b,f]azepine [5] motifs have previously been reported in enantioselective allylic displacement [3j, 6] and conjugate addition [7] reactions. As the exploration of these and related ligand types continues to evolve, their use in novel processes will increase. Herein, we report an asymmetric intramolecular Rh-catalyzed hydroacylation [8] reaction of pent-4-enals for the preparation of cyclopentanones [Eq. (1)]. Two key features of the catalytic system are noteworthy: this is the first time phosphoramiditealkene ligands have been used for this reaction type and the incorporation of an achiral phosphine coligand is necessary to promote enantioselective catalysis.After the seminal report in 1972 [9] by Sakai et al., in which stoichiometric Rh I was used, Miller and co-workers [10] and Larock et al. [11] showed that substituted g-pentenals undergo hydroacylative cycloisomerization using [Rh(PPh 3 ) 3 Cl]. Their protocol featured solvent saturated with ethylene and necessitated high catalyst loading (up to 50 mol %); additionally, they noted the formation of considerable amounts of side products from competitive decarbonylation pathways. Bosnich and co-workers [12] and Sakai et al. [13] independently reported catalytic enantioselective intramolecular hydroacylation with cationic rhodium perchlorate catalysts prepared from binap or Me-DuPhos. [14] These studies showed that to obtain good product selectivity the matching of the diphosphine ligand to the pentenal substrates was of the utmost importance. Subsequent investigations with isotopic labelling have also been undertaken to shed light on the mechanistic details. [10,15] It has been suggested that the benefits of ethylene in the reaction mixture, mentioned in the early reports, arise from the formation of a coordinatively saturated cationic rhodium species stabilized against decomposition. [10,11] This aspect of using ethylene piqued our interest and led us to examine the use of donor ligands incorporating an olefin. Additionally, we envisioned the implementation of combinatorial catalysis [16] involving heteroleptic complexes generated in situ, an approach that is highly rewarding as illustrated by the observations of Reetz et al., [17] Shibasaki and co-workers, [18] and Ding and co-workers. [19] In prospecting experiments we examined pentenal 1 a, as the prototypical substrate, under various reaction conditions with complexes generated in situ from [{RhCl(C 2 H 4 ) 2 } 2 ] and phosphoramidite ligands (S)-L1 [6] and (R,R,R)-L2 [20] in the presence of Ag I (T...

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Section: Thomas J Hoffman and Erick M Carreira*mentioning

confidence: 99%

mentioning

confidence: 99%

Catalytic Asymmetric Intramolecular Hydroacylation with Rhodium/Phosphoramidite–Alkene Ligand Complexes

Hoffman

Carreira

2011

Angewandte Chemie

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“…The catalysts (S)-(+)-diphenyl-(1-methylpyrrolidin-2-yl) methanol (DPMPM) 4 8 and N,N-dibutylaminonorephedrine (DBNE) 6 10 were prepared following literature procedures. (-)-3-Exo dimethylaminoisoborneol (DAIB) 5 9 was synthetized from (+)-camphor following a slightly modified procedure as reported 9 using KOtBu as a base in the first step and MeI as the methylating agent in the final step.…”

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confidence: 99%

Enantioselective synthesis of furylalcohols by catalytic asymmetric addition of diethylzinc to furanaldehydes

vanOeveren

Menge

Feringa

et al. 1989

Tetrahedron Letters

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“…The reaction conditions of the asymmetric 1,4-additions to chalcones were optimized with the use of 5 mol % Cu-(acac) 2 are summarized in Table 1. In ligand 2a, having R 1 and R 2 as both H atoms, the asymmetric 1,4-addition of ZnEt 2 to the chalcone in toluene gave the product in 100% yield but with a low enantioselectivity of 14% ee (entry 1).…”

Section: Resultsmentioning

confidence: 99%

“…Recently, catalytic conjugate additions have attracted much attention. 1 The first breakthrough in using substoichiometric nickel complexes of ephedrine was demonstrated by Soai et al 2 In recent studies of metal-catalyzed 1,4-additions using Grignard or dialkylzinc reagents, chiral copper and nickel complexes are the most widely investigated catalytic systems for inducing high enantioselectivities. For chiral ligands, phosphorus amidites, 3 TADDOL-derived phosphates, 4 and biphenol-based phosphoramidites 5 had been established to have remarkable stereocontrol in the ZnEt 2 addition to cyclic enones.…”

Section: Introductionmentioning

confidence: 99%

Highly enantioselective conjugate addition of diethylzinc to substituted chalcones catalyzed by Cu(II) complexes of a tridentate P,N,O ligand

Biradar

Gau

2008

Tetrahedron: Asymmetry

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Catalytic asymmetric induction in enantioselective conjugate addition of dialkylzincs to enones

Cited by 78 publications

References 1 publication

Catalytic Asymmetric Intramolecular Hydroacylation with Rhodium/Phosphoramidite–Alkene Ligand Complexes

Catalytic Asymmetric Intramolecular Hydroacylation with Rhodium/Phosphoramidite–Alkene Ligand Complexes

Enantioselective synthesis of furylalcohols by catalytic asymmetric addition of diethylzinc to furanaldehydes

Highly enantioselective conjugate addition of diethylzinc to substituted chalcones catalyzed by Cu(II) complexes of a tridentate P,N,O ligand

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