α-fluorination of ketones by xenon and iodobenzene difluorides: A stereochemical evidence demonstrating their mechanistic differences

Tsushima, Tadahiko; Kawada, Kenji; Tsuji, Teruji

doi:10.1016/s0040-4039(00)87050-1

Cited by 48 publications

(14 citation statements)

References 17 publications

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“…Table 2 gives a complete overview of the experimental X-ray data and Table 3 compares the bond lengths and angles of these F-PCBs 3 presented in this work. There is considerable general interest in using organic fluorines to probe the mechanisms of biochemical reactions (Ojima et al, 1996;Tsushima et al, 1982), and the synthesis of organo-fluorine compounds for pharmaceutical and biochemical applications (Welch & Eswarakrishnan, 1991). The research described here is an investigation of the utilization of fluorine-tagged persistent organic pollutants (POPs) as new marker compounds for the determination of metabolic pathways.…”

Section: Introductionmentioning

confidence: 99%

Influence of fluoro-substitution on the planarity of 4-chlorobiphenyl (PCB 3)

Luthe¹,

Swenson²,

Robertson³

2007

Acta Crystallogr Sect B

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Accurate structure determinations by X-ray crystal analysis and computation using semi-empirical self-consistent field molecular orbital calculations are described and compared for five monofluorinated analogues of 4-chlorobiphenyl, i.e. 2-fluoro-4-chlorobiphenyl, 2'-fluoro-4-chlorobiphenyl, 3-fluoro-4-chlorobiphenyl, 3'-fluoro-4-chlorobiphenyl and 4'-fluoro-4-chlorobiphenyl. Intermolecular interactions for all monofluorinated isomers are dominated by phenyl-phenyl stacking and C-H-phenyl interactions. C-F bond lengths varied between 1.341 and 1.374 A, C-Cl between 1.733 and 1.765 A, and both correlate with electron-density differences as determined by (13)C NMR shifts. The interior ring angles at ipso-fluoro substitution increase up to 122.2-124.2 degrees due to hyperconjugation by 2p-pi-orbital overlapping, a phenomenon that was also reflected in the computer calculation. The angles of C-F and C-Cl relative to the aromatic ring for vicinal fluoro- and chloro substituents show an attraction, not a repulsion, between the adjacent F and Cl substituents. This finding is explained on the basis of electron donor and acceptor properties. The dihedral angles of ortho-substituted biphenyls show that monofluoro substitution results in slightly smaller increases compared with chlorine, while additional ortho-fluorination results in little further change in the dihedral angle. In contrast, ortho-chlorination strongly decreases the co-planarity. This is likely to be due to interior ring-angle distortion and the size of the halogen substituent. Fluoro substitution does indeed affect the planarity of the PCB3 analogues, but these effects are minor compared with chloro substitution. Fluorine tagging offers promise for use in in vitro and in vivo studies. Differences in computational versus measured data emphasize the need to use a variety of methods to ascertain the true nature of the physical properties of a compound.

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Section: Introductionmentioning

confidence: 99%

Influence of fluoro-substitution on the planarity of 4-chlorobiphenyl (PCB 3)

Luthe¹,

Swenson²,

Robertson³

2007

Acta Crystallogr Sect B

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“…Trimethylsilyl enol ethers of cycloalkanones are more reactive than the corresponding enol acetates and are also converted in high yield to the corresponding α-fluoro carbonyl derivatives with xenon difluoride 78 , but reaction with bis(trimethyl-silyl) acetal derived from phenylacetic acid gave no α-fluorophenylacetic acid and only cleavage of the O-silyl group occurred. Xenon difluoride reacts smoothly with various steroid silyl ethers in the absence of any acid catalyst to afford stereoselectively α-oriented α-fluoro ketones in good yields 79 , while 16-α-and 16-β-fluoro-17β-estradiol were also prepared from estron enols 80 (Scheme 22). SCHEME 22 Reaction of the t-butyldimethylsilyl enol ether of a protected dipeptide with xenon difluoride in a mixture of acetonitrile and 1,1,2-trichlorotrifluoroethane gave the fluoro ketone in 71% yield as a 1:1 mixture of diasteroisomers, while further transformation to enol ether and fluorination affords the difluoro ketone 81 Shellhamer and coworkers studied the reactions of xenon difluoride in methanol in the presence of various olefins, and found that the course of the reaction depends strongly on the catalyst used.…”

Section: B Reactions Of Xenon Fluorides With Alkenesmentioning

confidence: 99%

Functionalization of Organic Molecules by Xenon Fluorides

Zupan

2009

Patai's Chemistry of Functional Groups

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“…With these considerations in mind, we wondered whether a carbonylative Negishi‐type coupling of 2‐iodoglycals with alkyl halides would be feasible (Scheme b). Unlike previous reports (Scheme a), this process would deliver valuable alkyl‐ketones bearing acidic α‐protons that can give rise to a rich variety of enolate‐based functionalizations, such as electrophile trapping, de novo synthesis of heterocycles, α‐arylation, hydrogen‐borrowing alkylation, α‐fluorination, etc.…”

Section: Introductionmentioning

confidence: 99%