Aerobic Co‑/N‑Hydroxysuccinimide-Catalyzed Oxidation of p-Tolylsiloxanes to p-Carboxyphenylsiloxanes: Synthesis of Functionalized Siloxanes as Promising Building Blocks for Siloxane-Based Materials

• Published in: Journal of the American Chemical Society Vol. 141; no. 5; pp. 2143 - 2151
• Main Authors: Goncharova, Irina K, Silaeva, Kseniia P, Arzumanyan, Ashot V, Anisimov, Anton A, Milenin, Sergey A, Novikov, Roman A, Solyev, Pavel N, Tkachev, Yaroslav V, Volodin, Alexander D, Korlyukov, Alexander A, Muzafarov, Aziz M
• Format: Journal Article
• Language: English
• Published: United States American Chemical Society 06-02-2019
• ISSN: 0002-7863; 1520-5126
• DOI: 10.1021/jacs.8b12600

Synthesis of organosilicon products with a “polar” functional group within organic substituents is one of the most fundamentally and practically important challenges in today’s chemistry of silicones. In our study, we suggest a solution to this problem, viz., a high-efficiency preparative method based on aerobic Co-/N-hydroxysuccinimide (NHSI) catalyzed oxidation of p-tolylsiloxanes to p-carboxyphenylsiloxanes. This approach is based on “green”, commercially available, simple, and inexpensive reagents and employs mild reaction conditions: Co­(OAc)2/NHSI catalytic system, O2 as the oxidant, process temperature from 40 to 60 °C, atmospheric pressure. This reaction is general and allows for synthesizing both mono- and di-, tri-, and poly­(p-carboxyphenyl)­siloxanes with p-carboxyphenyl groups at 1,1-, 1,3-, 1,5-, and 1,1,1-positions. All the products were obtained and isolated in gram amounts (up to 5 g) and in high yields (80–96%) and characterized by NMR, ESI-HRMS, GPC, IR, and X-ray data: p-carboxyphenylsiloxanes in crystalline state form HOF-like structures. Furthermore, it was shown that the suggested method is applicable for the oxidation of organic alkylarene derivatives (Ar–CH3, Ar–CH2–R) to the corresponding acids and ketones (Ar–C­(O)­OH and Ar–C­(O)–R), as well as hydride silanes ([Si]–H) to silanols ([Si]–OH). The possibility of synthesizing monomeric (methyl) and polymeric (siloxane-containing PET analogue, Sila-PET) esters based on 1,3-bis­(p-carboxyphenyl)­disiloxane was studied. These processes occur with retention of the organosiloxane frame and allow to obtain the corresponding products in 90 and 99% yields.