Highly Enantioselective Synthesis of Secondary Alcohols using Triphenylborane

Rudolph, Jens; Schmidt, Frank; Bolm, Carsten

doi:10.1002/adsc.200404067

Cited by 67 publications

(22 citation statements)

References 54 publications

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“…Braga demonstrated that the acceleration could be achieved by microwave irradiation 53. Based on Bolm's breakthrough, several aryl boron derivatives, such as triarylboranes42,43,49,54-57 and boroxines,52,58,59 were successfully employed in the asymmetric arylation of aldehydes. It is noteworthy that highly enantioselective late transition metal-based catalysts can also be employed with boronic acid derivatives 60-62…”

Section: Introductionmentioning

confidence: 99%

Practical Catalytic Asymmetric Synthesis of Diaryl-, Aryl Heteroaryl-, and Diheteroarylmethanols

2009

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Enantioenriched diaryl-, aryl heteroaryl-and diheteroarylmethanols exhibit important biological and medicinal properties. One-pot catalytic asymmetric syntheses of these compounds beginning from readily available aryl bromides are introduced. Thus, lithium-bromide exchange with commercially available aryl bromides and n-BuLi was followed by salt metathesis with ZnCl 2 to generate ArZnCl. A second equivalent of n-BuLi was added to form the mixed organozinc, ArZnBu. In the presence of enantioenriched amino alcohol-based catalysts, ArZnBu adds to aldehydes to afford essentially racemic diarylmethanols. The low enantioselectivities were attributed to a LiCl-promoted background reaction. To inhibit this background reaction, the chelating diamine TEEDA (tetraethylethylene diamine) was introduced prior to aldehyde addition. Under these conditions, enantioenriched diarylmethanols were obtained with >90% ee. Arylations of enals generated allylic alcohols with 81-90% ee. This procedure was unsuccessful, however, when applied to heteraryl bromides, which was attributed to decomposition of the heteroaryl lithium under the salt metathesis conditions. To avoid this problem, the metathesis was conducted with EtZnCl, which enabled the salt metathesis to proceed at low temperatures. The resulting EtZn(Ar Hetero ) intermediates (Ar Hetero =2-and 3-thiophenyl, 2-benzothiophenyl, 3-furyl, and 5-indolyl) were successfully added to aldehydes and heteroaryl aldehydes with enantioselectivities between 81-99%. These are the first examples of catalytic and highly enantioselective syntheses of diheteroarylmethanols. In a similar fashion, ferrocenyl bromide was used to generate FcZnEt and the ferrocenyl group added to benzaldehyde and heteroaromatic aldehydes to form ferrocene-based ligand precursors in 86-95% yield with 96-98% ee. It was also found that the arylation and heteroarylation of enals could be followed by diastereoselective epoxidations to provide epoxy alcohols with high enantio-and diastereoselectivities in a one-pot procedure.

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Section: Introductionmentioning

confidence: 99%

Practical Catalytic Asymmetric Synthesis of Diaryl-, Aryl Heteroaryl-, and Diheteroarylmethanols

2009

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“…Triarylboranes 5 and triarylalanes 6 have been also employed in enantioselective additions to both alkyl and aryl aldehydes with reasonable success. However, these reagents are not readily available, they deliver only a single aryl group, and they are pyrophoric, greatly diminishing their appeal.…”

Section: Introductionmentioning

confidence: 99%

Stereospecific Cross-Coupling of Secondary Organotrifluoroborates: Potassium 1-(Benzyloxy)alkyltrifluoroborates

2012

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Potassium 1-(alkoxy/acyloxy)alkyltrifluoroborates have been synthesized through a copper-catalyzed diboration of aldehydes and subsequent conversion of the resulting potassium 1-(hydroxy)alkyltrifluoroborates. The palladium-catalyzed Suzuki-Miyaura reaction employing the potassium 1-(benzyloxy)alkyltrifluoroborates with aryl and heteroaryl chlorides provides access to protected secondary alcohols in high yields. The β-hydride elimination pathway is avoided through use of the benzyl protecting group, which is proposed to stabilize the diorganopalladium intermediate by coordination of the arene to the metal center. This cross-coupling is stereospecific with complete retention of stereochemistry.

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“…Bolm et al reported that the asymmetric phenyl transfer reaction proceeds with an inexpensive triphenylborane as aryl source in the presence of chiral ferrocene based catalyst 65 (Table 17) [117]. In this method, a long preparation period in the boron-to-zinc exchange reaction is unnecessary, although excess amounts of a Ph-source and Zn-source are required.…”

Section: 5enantioselective Arylation To Aldehydesmentioning

confidence: 98%

Recent Progress in Selective Additions of Organometal Reagents to Carbonyl Compounds

Hatano¹,

Miyamoto²,

Ishihara

2007

COC

108

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Carbon-carbon bond forming reactions are simple and direct methods for synthesizing the various skeletons and the diverse structures of organic compounds. Even 100 years after the discovery of the Grignard reaction, organomagnesium, organolithium, and organoaluminum remain popular for carbon-carbon bond formation reactions in modern organic chemistry. Moreover, asymmetric alkyl-or aryl-additions to carbonyl compounds with organometal reagents is attractive due to the enantioselective synthesis of chiral secondary alcohols, which sharply contrasts the enantioselective reduction of carbonyl compounds. Herein, we review recent progress in the selective addition to carbonyl compounds with organometal reagents, particularly Li, Mg, and Zn from both a classic viewpoint using metal ate complexes and from a catalytic enantioselective viewpoint using new chiral ligands.

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Highly Enantioselective Synthesis of Secondary Alcohols using Triphenylborane

Abstract: Dedicated to Joe P. Richmond on the occasion of his 60 th birthday.Abstract: Asymmetric phenyl transfer reactions with triphenylborane as aryl source and a ferrocene-based catalyst give secondary alcohols in high yields and excellent enantioselectivities.

Cited by 67 publications

References 54 publications

Practical Catalytic Asymmetric Synthesis of Diaryl-, Aryl Heteroaryl-, and Diheteroarylmethanols

Practical Catalytic Asymmetric Synthesis of Diaryl-, Aryl Heteroaryl-, and Diheteroarylmethanols

Stereospecific Cross-Coupling of Secondary Organotrifluoroborates: Potassium 1-(Benzyloxy)alkyltrifluoroborates

Recent Progress in Selective Additions of Organometal Reagents to Carbonyl Compounds

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