Synthesis of highly substituted alkenes by sulfur-mediated olefination of N-tosylhydrazones

• Published in: Communications chemistry 2023-11, Vol.6 (1), p.255-255, Article 255
• Main Authors: Conen, Peter, Nickisch, Roman, Meier, Michael A. R.
• Format: Article
• Language: English
• Subjects: 639/638/224/685; 639/638/403/933; 639/638/403/934; 639/638/549/933; 639/638/77/889; Additives; Alkenes; Alkylidene; Chemical synthesis; Chemistry; Chemistry and Materials Science; Chemistry/Food Science; Cross coupling; Electrochemical analysis; Emission; Optical measuring instruments; Optical properties; Organometallic compounds; Potassium carbonate; Reagents; Substitutes; Substrates; Sulfur
• ISSN: 2399-3669; 2399-3669
• DOI: 10.1038/s42004-023-01058-2

Tetraphenylethylenes (TPEs) are well-known for their aggregation-induced emission properties. The synthesis of TPE derivatives, as well as other highly substituted olefins, generally requires the use of hazardous reagents, such as metalorganic compounds, to overcome the high activation energies caused by the sterically congested double bond. Herein, we present an efficient and metal-free procedure for the synthesis of tetraarylethylenes via alkylidene-homocoupling of N -tosylhydrazones, derived from readily available benzophenones, in excellent yields. The method relies only on cheap and benign additives, i.e . elemental sulfur and potassium carbonate, and easily competes with other established procedures in terms of scope, yield and practicability. A mechanistic study revealed a diazo compound, a thioketone and a thiirane as key intermediates in the pathway of the reaction. Based on this, a modified method, which allows for selective alkylidene-cross-coupling, generating a broader scope of tri- and tetrasubstituted olefins in good yields, is showcased as well. Tetraphenylethylenes (TPEs) are known for their aggregation-induced emission and electrochemical properties of value for optical sensors, however, established synthetic routes suffer from several limitations. Here, the authors develop a metal-free route to TPEs and other alkenes via a sulfur-mediated coupling of N -tosylhydrazones, achieving good yields and a broad substrate scope.