- 1,4-Diazabicyclo[2.2.2]octane (DABCO)- an efficient reagent in the synthesis of alkyl tosylates or sulfenates
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The bieyclic tertiary amine 1,4-diazabicyclo[2.2.2]octane (DABCO) is 8 promising substitute not only for the widely used but hazardous and hygroscopic base pyridine in the syntheses of alkyl tosylates 3 but also for triethylamine in the preparation of alk
- Hartung, Jens,Huenig, Siegfried,Kneuer, Rainer,Schwarz, Michaela,Wenner, Hermann
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- Epimerization of Tertiary Carbon Centers via Reversible Radical Cleavage of Unactivated C(sp3)-H Bonds
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Reversible cleavage of C(sp3)-H bonds can enable racemization or epimerization, offering a valuable tool to edit the stereochemistry of organic compounds. While epimerization reactions operating via cleavage of acidic C(sp3)-H bonds, such as the Cα-H of carbonyl compounds, have been widely used in organic synthesis and enzyme-catalyzed biosynthesis, epimerization of tertiary carbons bearing a nonacidic C(sp3)-H bond is much more challenging with few practical methods available. Herein, we report the first synthetically useful protocol for the epimerization of tertiary carbons via reversible radical cleavage of unactivated C(sp3)-H bonds with hypervalent iodine reagent benziodoxole azide and H2O under mild conditions. These reactions exhibit excellent reactivity and selectivity for unactivated 3° C-H bonds of various cycloalkanes and offer a powerful strategy for editing the stereochemical configurations of carbon scaffolds intractable to conventional methods. Mechanistic study suggests that the unique ability of N3? to serve as a catalytic H atom shuttle is critical to reversibly break and reform 3° C-H bonds with high efficiency and selectivity.
- Wang, Yaxin,Hu, Xiafei,Morales-Rivera, Cristian A.,Li, Guo-Xing,Huang, Xin,He, Gang,Liu, Peng,Chen, Gong
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supporting information
p. 9678 - 9684
(2018/07/21)
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- Low-temperature x-ray structural studies of the ester and ether derivatives of cis- and trans-4-tert-butyl cyclohexanol and 2-adamantanol: Application of the variable oxygen probe to determine the relative σ-donor ability of C-H and C-C bonds
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Results of low-temperature X-ray structural studies for five cis-, and three trans-4-tert-butyl cyclohexanol, and six 2-adamantanol ester and ether derivatives are reported. Plots of C-OR bond distance against pKa(ROH) for derivatives of axial alcohol (5), equatorial alcohol (6) and 2-adamantanol derivatives (7) give slopes of -2.77 × 10-3, -2.86 × 10-3 and -3.05 × 10-3, respectively. Given that the relative differences in the slopes are modest, no clear distinction can be made about the relative σ-donor ability of a C-H bond and a C-C bond.
- Spiniello, Marisa,White, Jonathan M.
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p. 3094 - 3101
(2007/10/03)
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- Acid-catalyzed Rearrangement of O-4-tert-Butylcyclohexyl Methylthiocarbamates
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The geometrical isomers of O-4-tert-butylcyclohexyl methylthiocarbamate were prepared by way of the corresponding dithiocarbamates.The O-trans-isomer was obtained from a mixture of cis- and trans-4-tert-butylcyclohexanols via an alkoxide formation involvi
- Fujii, Kunio,Shuto, Yoshihiro,Kinoshita, Yoshiro
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p. 2379 - 2384
(2007/10/02)
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