- Selective Carbonyl?C(sp3) Bond Cleavage To Construct Ynamides, Ynoates, and Ynones by Photoredox Catalysis
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Carbon–carbon bond cleavage/functionalization is synthetically valuable, and selective carbonyl?C(sp3) bond cleavage/alkynylation presents a new perspective in constructing ynamides, ynoates, and ynones. Reported here is the first alkoxyl-radical-enabled carbonyl?C(sp3) bond cleavage/alkynylation reaction by photoredox catalysis. The use of novel cyclic iodine(III) reagents are essential for β-carbonyl alkoxyl radical generation from β-carbonyl alcohols, including alcohols with high redox potential (EoxP>2.2 V vs. SCE in MeCN). β-Amide, β-ester, and β-ketone alcohols yield ynamides, ynoates, and ynones, respectively, for the first time, with excellent regio- and chemoselectivity under mild reaction conditions.
- Jia, Kunfang,Pan, Yue,Chen, Yiyun
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supporting information
p. 2478 - 2481
(2017/02/23)
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- Investigation on the regioselectivities of intramolecular oxidation of unactivated C-H bonds by dioxiranes generated in Situ
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We found that dioxiranes generated in situ from ketones 1-6 and Oxone underwent intramolecular oxidation of unactivated C-H bonds at δ sites of ketones to yield tetrahydropyrans. From the trans/cis ratio of oxidation products 1a and 2a as well as the retention of the configuration at the δ site of ketone 5, we proposed that the oxidation reaction proceeds through a concerted pathway under a spiro transition state. The intramolecular oxidation of ketone 6 showed the preference for a tertiary δ C-H bond over a secondary one. This intramolecular oxidation method can be extended to the oxidation of the tertiary γ′ C-H bond of ketones 9 and 10. For ketone 11 with two δ C-H bonds and one γ′ C-H bond linked respectively by a sp3 hydrocarbon tether and a sp2 ester tether, the oxidation took place exclusively at the δ C-H bonds. Finally, by introducing proper tethers, regioselective hydroxylation of steroid ketones 12-14 have been achieved at the C-17, C-16, C-3, and C-5 positions.
- Wong, Man-Kin,Chung, Nga-Wai,He, Lan,Wang, Xue-Chao,Yan, Zheng,Tang, Yeung-Chiu,Yang, Dan
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p. 6321 - 6328
(2007/10/03)
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