Recent applications of the (TMS)3SiH radical-based reagent

Abstract

This review article focuses on the recent applications of tris(trimethylsilyl)silane as a radical-based reagent in organic chemistry. Numerous examples of the successful use of (TMS)(3)SiH in radical reductions, hydrosilylation and consecutive radical reactions are given. The use of (TMS)(3)SiH allows reactions to be carried out under mild conditions with excellent yields of products and remarkable chemo-, regio-, and stereoselectivity. The strategic role of (TMS)(3)SiH in polymerization is underlined with emphasis on the photo-induced radical polymerization of olefins and photo-promoted cationic polymerization of epoxides.

Scheme 1

Mechanism of the reduction of a functional group by (TMS)₃SiH.

Scheme 2

Debromination by reaction with (TMS)₃SiH.

Scheme 3

Removal of hydroxy group via thiocarbonyl derivatives by reaction with (TMS)₃SiH.

Scheme 4

Removal of functional groups by reaction with (TMS)₃SiH.

Scheme 5

Hydrosilylation of alkenes by (TMS)₃SiH.

Scheme 6

Hydrosilylation of alkynes and silyldesulfonylation by (TMS)₃SiH.

Scheme 7

Removal of the X group using the (TMS)₃SiH/HOCH₂CH₂SH reducing system.

Scheme 8

Enantioselective hydrosilylation using the (TMS)₃SiH/RSH reducing system.

Scheme 9

Radical reactions in water using (TMS)₃SiH or (TMS)₃SiH/HOCH₂CH₂SH.

Scheme 10

Reduction and hydrosilylation reactions in water using (TMS)₃SiH.

Scheme 11

Reductive alkylation of alkenes by (TMS)₃SiH.

Scheme 12

Carbocycles construction using (TMS)₃SiH.

Scheme 13

Construction of furan-ring and cyclic amines using (TMS)₃SiH.

Scheme 14

Construction of nitrogen heterocycles using (TMS)₃SiH.

Scheme 15

Examples of unimolecular radical processes followed by oxidation.

Scheme 16

Examples of intermolecular carbon-carbon bond formation.

Scheme 17

Enantioselective radical reactions using (TMS)₃SiH as mediator.

Scheme 18

Fluoroalkyl radicals addition to C–C multiple bonds mediated by (TMS)₃SiH.

Scheme 19

Synthesis of cyclonucleosides mediated by (TMS)₃SiH.

Scheme 20

Two consecutive reductive cyclizations mediated by (TMS)₃SiH.

Scheme 21

Tandem cyclizations mediated by (TMS)₃SiH.

Scheme 22

Domino reactions mediated by (TMS)₃SiH.

Scheme 23

Radical cascade process mediated by (TMS)₃SiH.

Figure 1

Polymerization profiles of trimethylolpropane triacrylate. Benzophenone/ (TMS)₃SiH (1%/2%) vs. benzophenone/ethyldimethylaminobenzoate (1%/2%) in laminate.

Figure 2

Polymerization profiles of trimethylolpropane triacrylate. Photoinitiated system: (a) diphenyl (2,4,6-trimethylbenzoyl)-phosphine oxide (1% w/w) and (b) diphenyl (2,4,6-trimethylbenzoyl)-phosphine oxide/(TMS)₃SiH (1%/2% w/w) under air.

Figure 3

(1) Polymerization profiles of (3,4-epoxycyclohexane)methyl 3,4-epoxycyclohexyl-carboxylate (Uvacure 1500 from Cytec) under air. Upon a diode laser irradiation (405 nm) in the presence of (a) phenyl bis(2,4,6-trimethyl benzoyl)/Ph₂I⁺ (1%/1% w/w), (b) phenyl bis(2,4,6-trimethyl benzoyl)/tetraphenyldisilane/Ph₂I⁺ (1%/3%/1% w/w), and (c) phenyl bis(2,4,6-trimethyl benzoyl)/(TMS)₃Si-H/Ph₂I⁺ (1%/3%/1% w/w). (2) Conversion of the SiH content in the cases of (b) and (c).

Scheme 24

Photoredox catalysis using (TMS)₃SiH.

Figure 4

Polymerization profiles of (3,4-epoxycyclohexane)methyl 3,4-epoxycyclohexyl-carboxylate (Uvacure 1500 from Cytec) under air in the presence of (a) Ir(ppy)₃/(TMS)₃Si-H/Ph₂I⁺ (0.2%/3%/2% w/w) upon a blue LED bulb; (b) Ru(phen)₃²⁺/(TMS)₃Si-H/Ph₂I⁺ (0.2%/3%/2% w/w) upon a white LED bulb irradiation.

Figure 5

Polymerization process of an acrylate matrix (Ebecryl 605 from Cytec) initiated at RT under air for different initiating systems: (a) Cumene hydroperoxide/Cobalt (II) salt/(TMS)₃SiH; (b) Cumene hydroperoxide/Cobalt (II) salt.