Environment Friendly Process toward Functional Polyorganosiloxanes with Different Chemical Structures through CuAAC Reaction

Abstract

Despite the presence of many methods, which were created to date for the preparation, functionalization, and vulcanization of polysiloxanes, the development of materials based on silicones remains relevant and requires the introduction of new approaches that combine such modern strategies as atom-economical reactions, refusal to use harmful and dangerous organochlorosilanes, and using the principles of green chemistry and minimizing the use of solvents. In this work, we develop modern approaches to the preparation of both linear and branched polyorganosiloxanes containing azidopropyl functions at the silicon atom. In the first part of the work, it was shown that the proposed method for introducing these groups by catalytic rearrangement with the opening of cyclosiloxane is effective and makes it possible to obtain polysiloxanes with different contents of azidopropyl groups and different molecular weights. The second part of the work demonstrated the possibility of postpolymerization functionalization of such polymers by the mechanism of azide–alkyne cycloaddition under “green” conditions, without using solvents and amines. All of the most important functional fragments were introduced into the structures of organosilicon polymers by a single mechanism, under simple conditions, without the use of expensive catalysts, exposure to irradiation, and hazardous solvents. The combination of simplicity and versatility in the preparation of polysiloxanes with azidopropyl groups with the possibility of performing a click reaction makes it possible to directionally obtain the required materials based on universal raw materials and, as a result, can open up broad prospects for serious development and rethinking of the chemistry of silicones.

Environmentally Friendly Synthesis and Self‐Catalytic Hydrolysis of Triazole‐Modified Organosilanes for Polysiloxane Production

“…In our previous work, [30] we proposed to carry out the reaction of CuAAC with azide‐containing polydimethylsiloxanes with various chain lengths and various arrangements of functional groups with a wide range of ethynyl substrates using commercially available copper bromide (CuBr) as a catalyst in a relatively small amount (3–5 mol%). The process was carried out in bulk or in the presence of the “green solvent” ethyl acetate.…”

“…The authors have cited additional references within the Supporting Information. [30,31] The Supporting Information includes description of methods for studying the obtained compounds, synthetic procedures for obtaining substrates 3-1 -3-20, and 4-1 -4-7, as well as spectroscopic data of compounds, copies of 1 H NMR, 13 C NMR and 29 Si NMR spectra for compounds, copies of IR spectra for compounds and copies of HPMS data for compounds.…”

Optimized synthesis of functional organosilicon monomers and polymers exploiting new types of CuAAC recoverable heterogeneous catalysts

“…26,27 The discovery and development of the Cu(I)-catalyzed azide-alkyne cycloaddition (CuAAC) reaction in the last 20 years [28][29][30][31][32] has led to the rapid development of chemistry from medical applications and the synthesis of simple molecules to the creation of complex polymeric and supramolecular structures, [33][34][35][36][37][38] including organosilicon chemistry. [39][40][41][42][43][44][45] The culmination of any chemical, and especially a "click" process, which opens up its industrial prospects, is, of course, its efficient implementation under heterogeneous conditions, which greatly facilitates the isolation of the final reaction product and allows the reuse of the catalyst, 46,47 and such processes are actively being developed and studied for the CuAAC reaction in its various applications, 31,[48][49][50][51][52] however, they are still completely absent in the chemistry of creating organosilicon molecules and practically absent in polymer chemistry.…”

“…The discovery and development of the Cu( i )-catalyzed azide–alkyne cycloaddition (CuAAC) reaction in the last 20 years 28–32 has led to the rapid development of chemistry from medical applications and the synthesis of simple molecules to the creation of complex polymeric and supramolecular structures, 33–38 including organosilicon chemistry. 39–45…”

Facile Synthesis of Sulfur-Containing Functionalized Disiloxanes with Nonconventional Fluorescence by Thiol–Epoxy Click Reaction

“…Click reactions have attracted specific attention because of their intriguing features, such as mild reaction conditions, fast speed, high yield, and brilliant tolerance of functional groups [17][18][19]. The azide-alkyne reaction [20], thiol-ene reaction [21,22], and aza-Michael addition reaction [23,24] with the "click" feature have all been widely used to prepare organosilicon compounds [21], functionalized polysiloxanes [20,[25][26][27], and silicone elastomers [28] by us and other groups, and thus have become mature or semi-mature organosilicon synthetic methodologies. From the standpoint of existing raw materials, these strategies require azide-(or alkyl), thiol-, vinyl-, and aminecontaining silanes or (poly)siloxanes, most of which have relatively high costs except vinyl-containing materials.…”