Poly(methylhydrosiloxane)

Description

Poly(methylhydrosiloxane) is a reducing agent. For example, it can be used for the reduction of esters to alcohols as well as the reduction of aldehydes and ketone. It can also be used for the reduction of phosphine oxides to phosphine. Recent study has also used it for conjugate reduction of α, β-Unsaturated Carbonyl and Carboxyl Compounds. Finally, it is also used in greener amine synthesis mediated by reductive amination which is an alternative to borohydrides.

Chemical properties

Colorless liquid

The Uses of Poly(methylhydrosiloxane)

Polymethylhydrosiloxane(PMHS) is an easily handled,inexpensive,non-toxic,and mild reducing agent. PMHS is attractive as a substitute for more expensive or hazardous silanes or siloxanes and as the stoichiometric reductant in catalytic organotin-mediated processes. It can be cross linked by metal catalyst at low temperature to form waterproof membrane. It is used as waterproof agent of textile, glass, pottery, paper, leather, metal, cement and marble etc, especially in textile waterproof. It is used as insulator and cross linker of paper. Poly(methylhydrosiloxane) is used in the reduction of esters to alcohols, catalyzed by a combination of titanocene dichloride and either n-BuLi or EtMgBr. It is a safer alternative to triethoxysilane, B22063, for reduction of phosphine oxides to phosphines, catalyzed by Ti(O-i-Pr)4. It is also used in greener amine synthesis by reductive amination as an alternative to borohydrides.

Preparation

Poly(methylhydrosiloxane) is prepared by hydrolysis of methyldichlorosilane followed by heating (60–150℃) the resultant mixture of cyclic silanes in the presence of hexamethyldisiloxane generates the linear polysiloxane.

General Description

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Harnessing the reactivity of poly(methylhydrosiloxane) for the reduction and cyclization of biomass to high-value products

Synthesis

Poly(methylhydrosiloxane)(PMHS) is synthesized by the controlled hydrolysis of MeSiHCl₂^[1]. 

Advantages

PMHS is synthesized by the controlled hydrolysis of MeSiHCl2, a byproduct in producing Me2SiCl2, a feedstock for the silicone industry. As a byproduct of the silicone industry, it is a cheap, easy to handle, and environmentally friendly reducing agent. PMHS is more air and moisture-stable than other silanes and can be stored for long periods of time without loss of activity. In addition to being synthesized from a waste product, PMHS is cheap, stable to air and moisture, and is considered nontoxic[2].

References

[1] HEIN N M, SEO Y, LEE S J, et al. Harnessing the reactivity of poly(methylhydrosiloxane) for the reduction and cyclization of biomass to high-value products?[J]. Green Chemistry, 2019, 10: 2662-2669. DOI:10.1039/C9GC00705A.
[2] Hein, Nicholas M. et al. “Harnessing the reactivity of poly(methylhydrosiloxane) for the reduction and cyclization of biomass to high-value products?.” Green Chemistry 10 (2019): 2662–2669.