In 2022,Ferretti, Francesco; Fouad, Manar Ahmed; Ragaini, Fabio published an article in Catalysts. The title of the article was 《Synthesis of Indoles by Palladium-Catalyzed Reductive Cyclization of β-Nitrostyrenes with Phenyl Formate as a CO Surrogate》.Safety of Ethyltriphenylphosphonium bromide The author mentioned the following in the article:
The synthesis of indoles by reductive cyclization of o-nitrostyrenes using Ph formate as a CO surrogate, using a palladium/1,10-phenanthroline complex as catalyst was recently reported. However, depending on the desired substituents on the structure, the use of β-nitrostyrenes as alternative reagents may be advantageous. The results of this study on the possibility to use Ph formate as a CO surrogate in the synthesis of indoles by reductive cyclization of β-nitrostyrenes, using PdCl2(CH3CN)2+phenanthroline as the catalyst was reported. It turned out that good results obtained when the starting nitrostyrene bears an aryl substituent in the alpha position. However, when no such substituent present, only fair yield of indole was obtained because the base required to decompose the formate also catalyzes an oligo-polymerization of the starting styrene. The reaction performed in a single glass pressure tube, a cheap and easily available piece of equipment. After reading the article, we found that the author used Ethyltriphenylphosphonium bromide(cas: 1530-32-1Safety of Ethyltriphenylphosphonium bromide)
Ethyltriphenylphosphonium bromide(cas: 1530-32-1) is a phase transfer catalyst, used to accelerate the cure of phenolic-based epoxy resins, certain fluoroelastomer resins and thermosetting powder coatings. CatOnium ETPB is also used as catalysts in the synthesis of certain organic compounds.Safety of Ethyltriphenylphosphonium bromide
Referemce:
Bromide – Wikipedia,
bromide – Wiktionary