587-03-1Relevant articles and documents
Photochemical substitution of polyhalogenothiophene and halogenothiazole derivatives
D'Auria, Maurizio,Distefano, Claudio,D'Onofrio, Franco,Mauriello, Giacomo,Racioppi, Rocco
, p. 3513 - 3518 (2000)
The irradiation of 2,3-diodo-5-nitrothiophene in the presence of aromatic and heteroaromatic compounds gave the corresponding 2-aryl derivatives in high yields. The irradiation of 2,4-diiodo-5-nitrothiophene under the same conditions gave the corresponding 2-aryl derivatives in low yields. The observed difference in the reactivity can be explained on the basis of the hypothesis that the homolytic cleavage of the carbon-iodine bond occurred in a π,π* triplet state. Computational results showed that the lowest triplet state of the 2,3-diiodo isomer is π,π*, while that of the 2,4-isomer is π,π*. The irradiation of 2-bromo-5-nitrothiazole in the presence of benzene or indene gave the corresponding 2-bromo-5-arylthiazole. This behaviour can be explained by considering that the lowest excited triplet state cannot allow the cleavage of the carbon-bromine bond thus electron transfer occurs and leads to the substitution of the nitro group. The photochemical substitution reactions on 2,3-diiodo-5-nitrothiophene can be carried out in large scale using a new flow reactor using a PFTE pipe.
Chemoselective (Hetero)Arene Electroreduction Enabled by Rapid Alternating Polarity
Hayashi, Kyohei,Griffin, Jeremy,Harper, Kaid C.,Kawamata, Yu,Baran, Phil S.
, p. 5762 - 5768 (2022/04/15)
Conventional chemical and even electrochemical Birch-type reductions suffer from a lack of chemoselectivity due to a reliance on alkali metals or harshly reducing conditions. This study reveals that a simpler avenue is available for such reductions by simply altering the waveform of current delivery, namely rapid alternating polarity (rAP). The developed method solves these issues, proceeding in a protic solvent, and can be easily scaled up without any metal additives or stringently anhydrous conditions.
Disproportionation of aliphatic and aromatic aldehydes through Cannizzaro, Tishchenko, and Meerwein–Ponndorf–Verley reactions
Sharifi, Sina,Sharifi, Hannah,Koza, Darrell,Aminkhani, Ali
, p. 803 - 808 (2021/07/20)
Disproportionation of aldehydes through Cannizzaro, Tishchenko, and Meerwein–Ponndorf–Verley reactions often requires the application of high temperatures, equimolar or excess quantities of strong bases, and is mostly limited to the aldehydes with no CH2 or CH3 adjacent to the carbonyl group. Herein, we developed an efficient, mild, and multifunctional catalytic system consisting AlCl3/Et3N in CH2Cl2, that can selectively convert a wide range of not only aliphatic, but also aromatic aldehydes to the corresponding alcohols, acids, and dimerized esters at room temperature, and in high yields, without formation of the side products that are generally observed. We have also shown that higher AlCl3 content favors the reaction towards Cannizzaro reaction, yet lower content favors Tishchenko reaction. Moreover, the presence of hydride donor alcohols in the reaction mixture completely directs the reaction towards the Meerwein–Ponndorf–Verley reaction. Graphic abstract: [Figure not available: see fulltext.].
Experimental and density functional theory studies on hydroxymethylation of phenylboronic acids with paraformaldehyde over a Rh-PPh3 catalyst
Wang, Kuan,Lan, Jie,He, Zhen-Hong,Cao, Zhe,Wang, Weitao,Yang, Yang,Liu, Zhao-Tie
, (2020/12/01)
The synthesis of benzyl alcohols (BAs) is highly vital for their wide applications in organic synthesis and pharmaceuticals. Herein, BAs was efficiently synthesized via hydroxymethylation of phenylboronic acids (PBAs) and paraformaldehyde over a simple Rh-PPh3 catalyst combined with an inorganic base (NaOH). A variety of BAs with the groups of CH3?, CH3O?, Cl?, Br?, and so on were obtained with moderate to good yields, indicating that the protocol had a good universality. Density functional theory (DFT) calculations proposed the Hayashi-type arylation mechanism involved the arylation step of PBA and Rh(OH)(PPh3)2 catalyst to form Rh(I)-bound aryl intermediates and the hydrolysis step of Rh(I)-bound aryl intermediates and HCHO to generate BA product (the rate-determining step). The present route provides a valuable and direct method for the synthesis of BAs and expands the application range of paraformaldehyde.
