- Bifunctional copper-based photocatalyst for reductive pinacol-type couplings
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A bifunctional copper-based photocatalyst has been prepared that employs a pyrazole-pyridine ligand incorporating a sulfonamide moiety that functions as an intramolecular hydrogen-bond donor for a photochemical PCET process. In typical reductive PCET processes, the photocatalyst and H-bond donor must have an appropriate redox potential and pKa, respectively, to promote the PCET. When working in concert in a bifunctional catalyst such as Cu(pypzs)(BINAP)BF4, the pKa of the H-bond donor can have an acidity that is orders of magnitude less and still efficiently promote the PCET process. A reductive pinacol-type coupling can be performed using a base-metal derived photocatalyst to afford valuable diols (24 examples, 46-99% yield), from readily available aldehydes and ketones.
- Caron, Antoine,Morin, émilie,Collins, Shawn K.
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p. 9458 - 9464
(2019/10/11)
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- The effect of Lewis acids on the pinacol homocoupling reaction of aldehydes promoted by samarium diiodide
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The effect of various Lewis acids on the samarium diiodide promoted pinacol homocoupling of aldehydes was investigated. The reaction of benzaldehyde proceeded with fair to good 1,2-anti-stereoselectivity, while in the case of other aromatic and aliphatic aldehydes syn-stereoselectivity was generally observed. Chiral α-alkylaldehydes allowed for an almost complete stereocontrol favoring syn-1,2-diols.
- Annunziata, Rita,Benaglia, Maurizio,Cinquini, Mauro,Raimondi, Laura
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p. 3369 - 3374
(2007/10/03)
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- Reductive coupling of carbonyl compounds to pinacols by using Sm-I2MeOH or Sm-I2-Ti(O(i)Pr)4-MeOH systems
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The coupling reaction of aromatic carbonyl compounds was performed with Sm-I2 or Sm-I2-Ti(O(i)Pr)4 in methanol. Meso isomer was mainly produced in the presence of Ti(O(i)Pr4.
- Yanada, Reiko,Negoro, Nobuyuki,Yanada, Kazuo,Fujita, Tetsuro
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p. 3271 - 3274
(2007/10/03)
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- SYNTHESIS OF BENZOFUROBENZOFURAN AND BENZOFUROBENZOFURAN
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A convenient method was developed for the synthesis of benzofurobenzofuran and benzofurobenzofuran by the structurally directed heterocyclization of hydrosalicyloin to 4b,9b-dihydrobenzofurobenzofuran or 5a,10b-dihydrobenzofurobenzofuran and their subsequent homolytic bromination and dehydrobromination in the presence of a base.The stuctures of the cyclization products are determined by the nature of the dehydrating agent.The possible mechanism of the cyclization of hydrosalicyloin in the presence of acids is disscused.
- Tolmach, E. L.,Kudryavtsev, A. B.,Zheltov, A. Ya.,Stepanov, B. I.
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p. 1594 - 1601
(2007/10/02)
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