Catalytic <i>atropo</i>-Enantioselective Reduction of Biaryl Lactones to Axially Chiral Biaryl Compounds

Ashizawa, Tomoko; Tanaka, Saori; Yamada, Tohru

doi:10.1021/ol800802c

Cited by 87 publications

(36 citation statements)

References 29 publications

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“…153 With the β-ketoiminatocobalt(II) catalyst (( S , S )- 141 , Figure 11) various substituted optically active biaryl compounds were synthesized in good yields and high ee’s. Biaryl lactones required an increase in temperature to 50 °C for facile racemization of atropisomers.…”

Section: Dynamic Kinetic Resolutionsmentioning

confidence: 99%

Advances in Stereoconvergent Catalysis from 2005 to 2015: Transition-Metal-Mediated Stereoablative Reactions, Dynamic Kinetic Resolutions, and Dynamic Kinetic Asymmetric Transformations

et al. 2017

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An important subset of asymmetric synthesis is dynamic kinetic resolution, dynamic kinetic asymmetric processes and stereoablative transformations. Initially, only enzymes were known to catalyze dynamic kinetic processes but recently various synthetic catalysts have been developed. This review summarizes major advances in non-enzymatic, transition metal promoted dynamic asymmetric transformations reported between 2005 and 2015.

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Section: Dynamic Kinetic Resolutionsmentioning

confidence: 99%

Advances in Stereoconvergent Catalysis from 2005 to 2015: Transition-Metal-Mediated Stereoablative Reactions, Dynamic Kinetic Resolutions, and Dynamic Kinetic Asymmetric Transformations

et al. 2017

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“…In fact, we have already demonstrated this hypothesis with the correlation between the enantioselectivity of the product and the HPLC analysis of the atropo-isomerization of a biaryl lactone at various temperatures. 4 In this communication, microwave irradiation under strictly controlled temperature conditions was applied to the Corey BakshiShibata (CBS) reduction of biaryl lactones with dynamickinetic resolution to verify the reaction acceleration with high enantioselectivities. …”

mentioning

confidence: 99%

“…Chiral HPLC analysis of the biaryl lactones was performed to reveal the suitable reaction temperatures corresponding to each substrate. 4 Therefore, the racemization rates of the optically active biaryl lactone 1e were measured at the same temperature under both the Table 1. CBS reduction of the biaryl lactone using a multimode-type microwave reactor The accurate internal reaction temperature was monitored by a fiber-optic sensor (Entries 1, 3, and 6) and a thermocouple sensor (Entries 2, 4, 5, and 7).…”

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confidence: 99%

Extraordinary Microwave Effect on atropo-Enantioselective Catalytic Reduction of Biaryl Lactones

2013

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It was found that microwave irradiation under strictly controlled temperature conditions drastically enhanced the catalytic atropo-enantioselective CoreyBakshiShibata (CBS) reduction of biaryl lactones. Since the high enantioselectivity was maintained completely compared with conventional heating conditions, the present enhancement is not caused by simple microwave heating. It was also revealed that the microwave irradiation could accelerate the racemization of the atropoenantiomers of optically active biaryl lactone. It could be concluded that the drastic enhancement with retention of the high enantioselectivity was caused not by simple heating, but by some direct microwave effect on the substrate molecule.Microwave irradiation in various organic syntheses has great advantages over conventional heating for shortening reaction times and improving chemical yields and selectivities. The reaction acceleration mechanism was generally assumed to be a simple thermal effect; however, tremendous effects have sometimes been observed, which cannot be explained merely by a simple thermal effect.2 This was still controversial. We have already reported the remarkable effect of microwave irradiation on the atropo-enantioselective methanolysis of biaryl lactones using the AgBF 4 phosphine complex with dynamickinetic resolution (Scheme 1).3 It was confirmed that the reaction was enhanced under microwave irradiation conditions without any loss of enantioselectivity compared with conventional conditions using an external heating block for temperature control at the same reaction temperature. Since the Arrhenius plot showed that the enantioselectivity decreased clearly with increasing internal reaction temperature, it was suggested that the reaction acceleration was not caused by simple heating.For the product to be obtained in high yield with high enantioselectivity during this reaction, quick equilibrium between the M-and P-isomers of biaryl lactone is required. In fact, we have already demonstrated this hypothesis with the correlation between the enantioselectivity of the product and the HPLC analysis of the atropo-isomerization of a biaryl lactone at various temperatures. 4 In this communication, microwave irradiation under strictly controlled temperature conditions was applied to the Corey BakshiShibata (CBS) reduction of biaryl lactones with dynamickinetic resolution to verify the reaction acceleration with high enantioselectivities. 5A multimode-type microwave reactor (Eyela, WaveMagic 1000S) was employed for the microwave irradiation reaction with a reference using an external heating block (Eyela, ChemStation PPS 5510 and PPS 5511). A fiber-optic sensor (thermometer: AMOTH FL-2000; probe: FS100-2M) was used to monitor the accurate internal reaction temperature under microwave irradiation conditions, while a thermocouple sensor (thermometer: AM 8000K; probe: K type) was used for the heating block.6 Both reactions were performed under a nitrogen atmosphere with the same size glassware made of the same material by the same g...

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“…Previously, we studied the catalytic enantioselective ring-opening reaction of biaryl lactone derivatives with axial chirality 4) . These reactions had already been extensively studied by Bringmann's group 5) , but most of the reported systems were stoichiometric reactions.…”

Section: Enantioselective Ring-opening Reaction Of Biaryl Lactones VImentioning

confidence: 99%

Microwave-specific Effect on Enantioselective Reactions

Sawada

Yamada

2018

J. Jpn. Petrol. Inst.

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Microwave irradiation is widely applied to organic synthesis. Many advantages of microwave irradiation, including drastic shortening of reaction time, suppression of side reactions, and/or higher chemical yield, have been proposed. Generally, these effects have been understood merely as a simple thermal effect, since microwave irradiation rapidly raises the temperature of the reaction mixture. However, some observed results could not be understood only by the thermal effect. Recently our group reported that several enantioselective reactions were accelerated under microwave irradiation without loss of enantioselectivity. As these extraordinary results could not be explained by the simple thermal effect, the concept of the "microwave-specific effect" should be considered. We describe our recent experimental results to elucidate the microwave-specific effect. Investigations are described on enantioselective ring-opening reactions of biaryl lactone derivatives, racemization of an optically pure biaryl lactone derivative, enantioselective Claisen rearrangement reaction, enantioselective Conia-ene reaction and ring-closing metathesis reaction. These reactions or racemization of optically pure compounds were accelerated under microwave conditions. Such reaction acceleration of enantioselective reactions was observed without loss of enantioselectivity.

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Catalytic atropo-Enantioselective Reduction of Biaryl Lactones to Axially Chiral Biaryl Compounds

Cited by 87 publications

References 29 publications

Advances in Stereoconvergent Catalysis from 2005 to 2015: Transition-Metal-Mediated Stereoablative Reactions, Dynamic Kinetic Resolutions, and Dynamic Kinetic Asymmetric Transformations

Advances in Stereoconvergent Catalysis from 2005 to 2015: Transition-Metal-Mediated Stereoablative Reactions, Dynamic Kinetic Resolutions, and Dynamic Kinetic Asymmetric Transformations

Extraordinary Microwave Effect on atropo-Enantioselective Catalytic Reduction of Biaryl Lactones

Microwave-specific Effect on Enantioselective Reactions

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