An efficient preparative method for the synthesis of siloxanols based on aerobic Co(OAc)2 or Cu(OAc)2/NHPI-catalyzed oxidation of hydride siloxanes has been proposed.

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, O 2 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−CH 3 , Ar−CH 2 −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.

A methodology for synthesizing a wide range of dumbbell‐shaped, graft and bottlebrush polymers with all‐siloxane nature (without carbosilane linkers) is suggested. These macroarchitectures are synthesized from SiOH‐containing compounds—silanol (Et3SiOH) and siloxanol dendrons of the first and second generations, with various peripheral substituents (Me or Et)—and from linear siloxanes comprising terminal and internal SiH groups by the Piers–Rubinsztajn reaction. Products and key building blocks are obtained in yields up to 95%. These polymers are heat and frost‐resistant siloxanes. As it turns out, the product physical properties are determined not only by the macromolecular structure, the linear chain length, the size and frequency of branched pendant, but also by the type of peripheral substituents—Me or Et—in the pendant. Thus, the viscosity of the graft polymers with branched pendant groups comprising peripheral Me‐groups is more than ≈3–5 fold lower than that of analogous polymers with peripheral Et‐groups.

The article presents an in-depth study of the applicability of cooperative [M]-/Organo-catalytic systems in aerobic SiÀ Hfunctionalization. A thorough kinetic study allowed us to identify two "complementary" catalytic systems based on earthabundant [M]-catalysts and inexpensive commercially available organic catalysts. The first system, Co(OAc) 2 /N-hydroxysuccinimide, made it possible to oxidize a SiÀ H-group to a SiÀ OHgroup in a wide range of monomers, including previously unknown ones, that dramatically differ in their reactivity. However, this system failed in the case of oligomeric and polymeric substrates. This problem was solved by application of the Cu(OAc) 2 /N-hydroxyphthalimide system. A wide potential for gram-scale (50-100 g) preparation of SiÀ OH-containing products with molecular architectures of different complexity was revealed using the established "substrate-reactivity-catalytic system" relationship. In particular, previously unknown types of dumbbell-shaped and graft polymers were synthesized using alkoxysilanols.

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