Sequence‐Controlled Catalytic One‐Pot Synthesis of Siloxane Oligomers

Abstract

Silicones are highly valuable poly- and oligomeric materials with a broad range of applications due to their outstanding physicochemical properties. The core framework of silicone materials consists of siloxane (Si-O-Si) bonds, and thus, the development of efficient siloxane-bond-forming reactions has attracted much attention. However, these reactions, especially "catalytic" siloxane-bond-forming reactions that enable the selective formation of unsymmetrical siloxane bonds, remain relatively underdeveloped. On the other hand, controlled iteration has become a powerful tool for the sequence-controlled synthesis of poly- and oligomeric compounds. Recently, control over the siloxane sequence has been achieved by the one-pot iteration of a B(C F ) -catalyzed dehydrocarbonative cross-coupling of alkoxysilanes with hydrosilanes and a B(C F ) -catalyzed hydrosilylation of carbonyl compounds. Thus, it is now possible to generate linear, branched, and cyclic sequence-specific oligosiloxanes in a highly selective manner under chloride-free conditions.

Silylation of Alcohols, Phenols, and Silanols with Alkynylsilanes – an Efficient Route to Silyl Ethers and Unsymmetrical Siloxanes

“…[43,44] Also this time (the Si-O-Si bond formation), there are several established methods, which can be carried out in both stoichiometric [43,45,46] or catalytic manner. [47][48][49][50][51][52][53][54][55][56][57][58][59][60] To sum up, the vast majority of known O-silylation strategies is presented on Figure 1, including their main benefits and drawbacks. In terms of substrates' accessibility, the most straightforward method is the condensation between alcohols/silanols and halosilanes.…”

Barium Siloxides and Catalysed Formation of Si−O−Si' Motifs

“…[6] Yet, metalc atalysts, and af ortioriA e-based ones, have seldom been implemented in the controlled production of siloxanes, despite the commercial importance of oligo-and polysiloxanes. [21][22] Asymmetric R 3 SiÀOÀSiR' 3 siloxanesc an be prepared by conventional condensations involving as ilanol( with ab ase) or am etal silanolate and ah alosilane R 3 SiX, but thesep rotocols generate large amountso fw aste by-products. [23] Instead, ah andful of catalysed processes relyingo nl ate transition metalsa re known.…”

Catalytic Synthesis of Oligosiloxanes Mediated by an Air Stable Catalyst, (C6F5)3B(OH2)

“…The substitution process is catalyzed either by an acid or a base under equilibrium in which the polysiloxanes can also be degraded (Brinker and Scherer, 1990). Although a step-wise synthesis of oligosiloxane has been reported, it is still based on conventional condensation of silanols with chlorosilanes (Uchida et al, 1990;Matsumoto et al, 2018Matsumoto et al, , 2019. Other methods available in literature for the preparation of oligosiloxanes involve catalytic cross-coupling reactions of oxygen nucleophiles (e.g., alkoxysilanes, silanols, phenols, and ethers) with hydrosilanes (Brook, 2018;Zhang et al, 2020).…”