913-86-0Relevant academic research and scientific papers
Visible Light Induced Reduction and Pinacol Coupling of Aldehydes and Ketones Catalyzed by Core/Shell Quantum Dots
Xi, Zi-Wei,Yang, Lei,Wang, Dan-Yan,Feng, Chuan-Wei,Qin, Yufeng,Shen, Yong-Miao,Pu, Chaodan,Peng, Xiaogang
, p. 2474 - 2488 (2021/02/05)
We present an efficient and versatile visible light-driven methodology to transform aryl aldehydes and ketones chemoselectively either to alcohols or to pinacol products with CdSe/CdS core/shell quantum dots as photocatalysts. Thiophenols were used as proton and hydrogen atom donors and as hole traps for the excited quantum dots (QDs) in these reactions. The two products can be switched from one to the other simply by changing the amount of thiophenol in the reaction system. The core/shell QD catalysts are highly efficient with a turn over number (TON) larger than 4 × 104 and 4 × 105 for the reduction to alcohol and pinacol formation, respectively, and are very stable so that they can be recycled for at least 10 times in the reactions without significant loss of catalytic activity. The additional advantages of this method include good functional group tolerance, mild reaction conditions, the allowance of selectively reducing aldehydes in the presence of ketones, and easiness for large scale reactions. Reaction mechanisms were studied by quenching experiments and a radical capture experiment, and the reasons for the switchover of the reaction pathways upon the change of reaction conditions are provided.
A convenient pinacol coupling of diaryl ketones with B2pin2viapyridine catalysis
Jo, Junhyuk,Kim, Seonyul,Choi, Jun-Ho,Chung, Won-Jin
supporting information, p. 1360 - 1363 (2021/02/22)
A convenient, pyridine-boryl radical-mediated pinacol coupling of diaryl ketones is developed. In contrast to the conventional pinacol coupling that requires sensitive reducing metal, the current method employs a stable diboron reagent and pyridine Lewis base catalyst for the generation of a ketyl radical. The newly developed process is operationally simple, and the desired diols are produced with excellent efficiency in up to 99% yield within 1 hour. The superior reactivity of diaryl ketone was observed over monoaryl carbonyl compounds and analyzed by DFT calculations, which suggests the necessity of both aromatic rings for the maximum stabilization of the transition states.
CBZ6 as a Recyclable Organic Photoreductant for Pinacol Coupling
Wang, Hua,Qu, Jian-Ping,Kang, Yan-Biao
supporting information, p. 2900 - 2903 (2021/05/05)
A recyclable organic photoreductant (1 mol % CBZ6)-catalyzed reductive (pinacol) coupling of aldehydes, ketones, and imines has been developed. Irradiated by purple light (407 nm) using triethylamine as an electron donor, a variety of 1,2-diols and 1,2-diamines could be prepared. The oxidation potential of the excited state of CBZ6 is established as -1.92 V (vs saturated calomel electrode (SCE)). The relative high reductive potential enables the reductive coupling of carbonyl compounds and their derivatives. CBZ6 can be prepared in gram scale and is acid/base- or air-stable. It could be applied in large-scale photoreductive synthesis and recovered in high yield after the reaction.
GaN nanowires as a reusable photoredox catalyst for radical coupling of carbonyl under blacklight irradiation
Botton, Gianluigi,Cen, Yunen,Cheng, Shaobo,Li, Chao-Jun,Liu, Mingxin,Mi, Zetian,Rashid, Roksana T.,Tan, Lida
, p. 7864 - 7870 (2020/08/19)
Employing photo-energy to drive the desired chemical transformation has been a long pursued subject. The development of homogeneous photoredox catalysts in radical coupling reactions has been truly phenomenal, however, with apparent disadvantages such as the difficulty in separating the catalyst and the frequent requirement of scarce noble metals. We therefore envisioned the use of a hyper-stable III-V photosensitizing semiconductor with a tunable Fermi level and energy band as a readily isolable and recyclable heterogeneous photoredox catalyst for radical coupling reactions. Using the carbonyl coupling reaction as a proof-of-concept, herein, we report a photo-pinacol coupling reaction catalyzed by GaN nanowires under ambient light at room temperature with methanol as a solvent and sacrificial reagent. By simply tuning the dopant, the GaN nanowire shows significantly enhanced electronic properties. The catalyst showed excellent stability, reusability and functional tolerance. All reactions could be accomplished with a single piece of nanowire on Si-wafer. This journal is
Light-enabled metal-free pinacol coupling by hydrazine
Qiu, Zihang,Pham, Hanh D. M.,Li, Jianbin,Li, Chen-Chen,Castillo-Pazos, Durbis J.,Khaliullin, Rustam Z.,Li, Chao-Jun
, p. 10937 - 10943 (2019/12/23)
Efficient carbon-carbon bond formation is of great importance in modern organic synthetic chemistry. The pinacol coupling discovered over a century ago is still one of the most efficient coupling reactions to build the C-C bond in one step. However, traditional pinacol coupling often requires over-stoichiometric amounts of active metals as reductants, causing long-lasting metal waste issues and sustainability concerns. A great scientific challenge is to design a metal-free approach to the pinacol coupling reaction. Herein, we describe a light-driven pinacol coupling protocol without use of any metals, but with N2H4, used as a clean non-metallic hydrogen-atom-transfer (HAT) reductant. In this transformation, only traceless non-toxic N2 and H2 gases were produced as by-products with a relatively broad aromatic ketone scope and good functional group tolerance. A combined experimental and computational investigation of the mechanism suggests that this novel pinacol coupling reaction proceeds via a HAT process between photo-excited ketone and N2H4, instead of the common single-electron-transfer (SET) process for metal reductants.
Bifunctional copper-based photocatalyst for reductive pinacol-type couplings
Caron, Antoine,Morin, émilie,Collins, Shawn K.
, p. 9458 - 9464 (2019/10/11)
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.
A novel method for pinacolic coupling of aromatic aldehydes and ketones with a Sm-ZnCl2 system
Guo, Hongyun,Zhang, Yongmin
, p. 284 - 286 (2007/10/03)
Sm-ZnCl2-system-mediated reductive coupling of aromatic aldehydes and ketones in THF-H2O at room temperature affords the corresponding pinacols in moderate to good yields.
Preparation of Condensed Aromatics by Superacidic Dehydrative Cyclization of Arvl Pinacols and Eooxides
Klumpp, Douglas A.,Baek, Donald N.,Prakash, G.K. Surya,Olah, George A.
, p. 6666 - 6671 (2007/10/03)
Aryl pinacols and epoxides, respectively, are cleanly and in high yield converted via superacidic dehydrative cyclization to the corresponding condensed aromatics. Dehydrative cyclization of benzopinacol (1a), triphenylacetophenone (2), and tetraphenylethylene oxide (9) give 9,10-diphenylphenanthrene (3a) as the major product in acidic media stronger than Ho = -11. Aryl pinacol 12a forms the condensed aromatic 13a as the major product in acidic media stronger than Ho = -13.5. It is proposed that the dehydrative cyclizations to provide aromatics 3a and 13a occurs through dicationic intermediates. Substituted benzopinacols 1f, 1g, and 1j are prepared and give the corresponding phenanthrenes (3f, 3g, and 3j) in high yields. The regiochemistry of the cyclization of substituted benzopinacols is controlled by deactivating substituents on the aryl rings. Aryl pinacols (12a-d) derived from acenaphthenequinone and pinacol 15 also give condensed aromatics (13a-d and 16, repectively) with superacidic triflic acid.
2-benzoylbenzoic acid: A photolabile mask for alcohols and thiols
Jones, Paul B.,Pollastri, Michael P.,Porter, Ned A.
, p. 9455 - 9461 (2007/10/03)
Photolysis of 2-benzoylbenzoate esters of primary and secondary alcohols 1 in the presence of a hydrogen donor (2-isopropanol) or an electron donor (primary amines) produces the corresponding alcohol in high yield. The fate of the benzoate is dependent on the conditions used for the photoreaction. In 2-propanol, the ketyl radical that derives from photoreduction dimerizes, to afford the benzpinacol product 3,3"-diphenylbiphthalidyl, 5. In the presence of amines the product is 3-phenylphthalide, 6, a benzhydrol derivative which is the result of simple reduction of the ketone followed by lactonization. While the photoproduct of the benzoate - 2-propanol reaction results from anticipated free radical chemistry, the amine-promoted reaction appears to result from a second, "dark", electron transfer process. We conclude that 2-benzoylbenzoic acid is an effective photolabile protecting group for primary and secondary alcohols, and preliminary studies indicate that thiols can be protected in an analogous way. Studies on the effect of benzophenone substituents and reaction solvent on the benzhydrol:benzpinacol product ratio provide mechanistic insight into the process.
