Enantioselective Carbenoid Insertion into Phenolic O–H Bonds with a Chiral Copper(I) Imidazoindolephosphine Complex

Osako, Takao; Panichakul, Duanghathai; Uozumi, Yasuhiro

doi:10.1021/ol202977j

Cited by 69 publications

(21 citation statements)

References 28 publications

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“…[15][16][17] The Cu-catalyzed O-H insertion of α-diazo esters is useful for the construction of α-alkoxycarbonyl structures, which are found in natural products and biologically active compounds. [18][19][20] A highly enantioselective version of this reaction has recently been accomplished with bisazaferrocene I, 21) Spirobox II, 17,[22][23][24][25][26] or the imidazoindolephosphine ligand III [27][28][29][30][31][32][33][34] (Fig. 2).…”

Section: Highlighted Paper Selected By Editor-in-chiefmentioning

confidence: 99%

“…However, there is still a need to develop other ligands for this type of reaction because the more versatile Box ligands IV and V are unsuitable. [21][22][23][24]26) In this context, we recently used our designed PCP-based Box ligands (S p )-1, in which two achiral oxazoline units are located at the meta positions of the spacer, in Cu-catalyzed O-H insertion reactions. We reported in a short communication that the ligands showed good enantioselectivities in intermolecular ethanolic and phenolic O-H insertions.…”

Section: Highlighted Paper Selected By Editor-in-chiefmentioning

confidence: 99%

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Planar Chiral [2.2]Paracyclophane-Based Bisoxazoline Ligands: Design, Synthesis, and Use in Cu-Catalyzed Inter- and Intramolecular Asymmetric O–H Insertion Reactions

Kitagaki

Murata

Asaoka

et al. 2018

CHEMICAL & PHARMACEUTICAL BULLETIN

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Centrally chiral bisoxazolines connected directly to a planar chiral [2.2]paracyclophane backbone were synthesized and evaluated as asymmetric ligands in Cu-catalyzed intermolecular ethanolic O-H insertion reactions of α-diazo esters. The reactivities and enantioselectivities of Cu complexes of the synthesized bisoxazoline ligands were lower than those of ligands without central chirality. However, planar chiral [2.2] paracyclophane-based bisoxazoline ligands with an inserted benzene spacer that had a sterically demanding isopropyl substituent showed good enantioselectivities in inter-and intramolecular aromatic O-H insertion reactions, without the aid of central chirality.

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Section: Highlighted Paper Selected By Editor-in-chiefmentioning

confidence: 99%

Section: Highlighted Paper Selected By Editor-in-chiefmentioning

confidence: 99%

Planar Chiral [2.2]Paracyclophane-Based Bisoxazoline Ligands: Design, Synthesis, and Use in Cu-Catalyzed Inter- and Intramolecular Asymmetric O–H Insertion Reactions

Kitagaki

Murata

Asaoka

et al. 2018

CHEMICAL & PHARMACEUTICAL BULLETIN

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“…The method affords high yields (86-99 %) and excellent enantioselectivities (94-99 % ee), proceeds under mild and neutral conditions, and affords cyclic ethers with 5-to 7-membered rings. [8] We began our study with intramolecular insertion into the phenolic O À H bond of methyl 2-diazo-3-(2-hydroxyphenyl)propanoate (2 a) catalyzed by a chiral copper catalyst prepared in situ from copper chloride, ligand (S a ,S,S)-1 a, and sodium tetrakis [3,5-bis(trifluoromethyl)phenyl]borate (NaBAr F ) ( Table 1, entry 1). The reaction was complete within 5 min and afforded 2-methoxycarbonyl 2,3-dihydrobenzofuran (3 a) in 69 % yield with 70 % ee.…”

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confidence: 99%

Enantioselective Copper‐Catalyzed Intramolecular Phenolic OH Bond Insertion: Synthesis of Chiral 2‐Carboxy Dihydrobenzofurans, Dihydrobenzopyrans, and Tetrahydrobenzooxepines

et al. 2013

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“…However, the desired OH insertion product (α‐phenoxy‐α‐phenylacetate) was obtained in 56 % yield with only 11 % ee . We6d and Uozumi and co‐workers6g used chiral copper spiro bisoxazoline complexes and a chiral copper imidazoindolephosphine complex, respectively, for the same reaction and also obtained extremely low ee values (10 % ee and 7 % ee , respectively).…”

Section: Methodsmentioning

confidence: 84%

Enantioselective Palladium‐Catalyzed Insertion of α‐Aryl‐α‐diazoacetates into the OH Bonds of Phenols

et al. 2014

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A palladium-catalyzed asymmetric O À H insertion reaction was developed. Palladium complexes with chiral spiro bisoxazoline ligands promoted the insertion of a-aryl-adiazoacetates into the OÀH bond of phenols with high yield and excellent enantioselectivity under mild reaction conditions. This palladium-catalyzed asymmetric O À H insertion reaction provided an efficient and highly enantioselective method for the preparation of synthetically useful optically active a-aryl-aaryloxyacetates.Palladium is an indispensable and versatile catalyst in modern organic synthesis.[1] Palladium efficiently catalyzes the cyclopropanation of olefins with diazomethane, a widely used carbene-transfer reaction, [2] and various new palladiumcatalyzed carbene-transfer reactions based on migratory insertion have recently been developed.[3] However, asymmetric palladium-catalyzed carbene-transfer reactions are rare and remain a challenge. The early examples of palladium-catalyzed asymmetric carbene-transfer reactions involved cyclopropanations and carbenylative amination, however, the resulting enantioselectivity was unsatisfactory. [4] Recently, Hu and co-workers [5] reported highly enantioselective palladium-catalyzed three-component reactions of pyrrole, diazoesters, and imines. Herein, we report a palladiumcatalyzed asymmetric insertion of a-aryl-a-diazoacetates into the O À H bond of phenols (Scheme 1).[6] Palladium complexes with chiral spiro bisoxazoline ligands efficiently catalyzed the OÀH insertion reaction, which provides a new method for the preparation of a-aryl-a-aryloxyacetates 3 with good yields and excellent enantioselectivity under mild, neutral reaction conditions.The a-aryl-a-aryloxyacetate moiety is ubiquitous in biologically active molecules [7] and it is also present in a chiral solvating agent for NMR spectroscopy [8] (Scheme 1). The established methodologies for the synthesis of optically active a-aryl-a-aryloxyacetates are based on either multistep transformations from chiral starting materials or the use of chiral auxiliaries. [7,8] To our knowledge, no highly enantioselective catalytic asymmetric method for preparing these important compounds has been reported. [9] The challenges lie mainly in the high acidity of the ahydrogen of a-aryl-a-aryloxyacetates. Because these compounds readily epimerize under basic conditions or at high temperature, any reliable method for their preparation should involve mild, neutral conditions. The transition-metal-catalyzed OÀH insertion reaction meets this requirement. In 2006, Maier and Fu [6c] attempted an OÀH bond insertion reaction between a-diazo-a-phenylacetates and phenols by using chiral copper bisazaferrocene complexes as catalysts. However, the desired O À H insertion product (a-phenoxy-aphenylacetate) was obtained in 56 % yield with only 11 % ee. We [6d] and Uozumi and co-workers [6g] used chiral copper spiro bisoxazoline complexes and a chiral copper imidazoindolephosphine complex, respectively, for the same reaction and also obtained extremely l...

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Enantioselective Carbenoid Insertion into Phenolic O–H Bonds with a Chiral Copper(I) Imidazoindolephosphine Complex

Cited by 69 publications

References 28 publications

Planar Chiral [2.2]Paracyclophane-Based Bisoxazoline Ligands: Design, Synthesis, and Use in Cu-Catalyzed Inter- and Intramolecular Asymmetric O–H Insertion Reactions

Planar Chiral [2.2]Paracyclophane-Based Bisoxazoline Ligands: Design, Synthesis, and Use in Cu-Catalyzed Inter- and Intramolecular Asymmetric O–H Insertion Reactions

Enantioselective Copper‐Catalyzed Intramolecular Phenolic OH Bond Insertion: Synthesis of Chiral 2‐Carboxy Dihydrobenzofurans, Dihydrobenzopyrans, and Tetrahydrobenzooxepines

Enantioselective Palladium‐Catalyzed Insertion of α‐Aryl‐α‐diazoacetates into the OH Bonds of Phenols

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