Bis(trimethylsilyl) Peroxide1

[5796-98-5]  · C6H18O2Si2  · Bis(trimethylsilyl) Peroxide  · (MW 178.38)

(a masked form of 100% hydrogen peroxide;2 synthon of HO+ for electrophilic hydroxylation;3,4 source of Me3SiO+ for electrophilic oxidations;4-6 a versatile oxidant for alcohols, ketones, phosphines, phosphites, and sulfides1,2,7)

Physical Data: bp 41 °C/30 mmHg;7 n20D 1.3970.1b

Solubility: highly sol aprotic organic solvents.

Form Supplied in: colorless oil; used as an anhydrous and protected form of hydrogen peroxide; 10% solution in hexane or in CH2Cl2.

Analysis of Reagent Purity: 1H NMR (s) d 0.18 ppm;3 29Si NMR d 27.2 ppm.8

Preparative Methods: obtained in 80-96% yields by reaction of Chlorotrimethylsilane with 1,4-Diazabicyclo[2.2.2]octane.(H2O2)2,3 Hexamethylenetetramine.H2O2,8 or Hydrogen Peroxide-Urea in CH2Cl2.9

Handling, Storage, and Precautions: thermally stable; can be handled in the pure state and distilled;8 rearranges at 150-180 °C.1c

Electrophilic Oxidations.

Bis(trimethylsilyl) peroxide (1) functions as an electrophilic hydroxylating agent for aliphatic, aromatic, and heteroaromatic anions.3 Reaction of their lithium or Grignard compounds with (1) often affords trimethylsiloxy intermediates, which undergo desilylation with HCl in methanol to give the corresponding alcohols in good yields. In the presence of a catalytic amount of Trifluoromethanesulfonic Acid, (1) reacts with aromatic compounds to produce the corresponding phenols after acidic workup.10 In these reactions the Me3SiO+ moiety is considered as a synthon of the hydroxyl cation (i.e. OH+).

Lithium or Grignard enolates of vinyl compounds react with (1) to produce the corresponding a-hydroxy ketones upon acidic workup.4 Treatment of enolate anions derived from carboxylic acids and amides with (1) in THF at rt gives the corresponding a-hydroxy derivatives in 31-58% yields.11 Furthermore, stereoselective synthesis of silyl enol ethers with retention of configuration is accomplished by oxidation of (E)- and (Z)-vinyllithiums, prepared from the corresponding bromides and s-BuLi, with (1) in THF at -78 °C.6 Heterocyclic silyl enol ethers, such as 3-(trimethylsiloxy)furan and 3-(trimethylsiloxy)thiophene, can be obtained by reaction of (1) with 3-lithiofuran and 3-lithiothiophene, respectively.5 In some reactions involving nucleophiles and (1), silylation may compete with siloxylation;3 the outcome depends upon the counterion.4

Oxidative Desulfonylation and Selective Baeyer-Villiger Oxidation.

Aliphatic, alicyclic, and benzylic phenyl sulfones react with n-BuLi and then with (1) in situ to give aldehydes or ketones in 66-91% yields (eq 1).12 On the other hand, reaction of ketones with (1) in the presence of a catalyst, such as Trimethylsilyl Trifluoromethanesulfonate,2 Tin(IV) Chloride, or Boron Trifluoride Etherate,7 in CH2Cl2 gives esters in good to excellent yields (eq 2). This Baeyer-Villiger oxidation proceeds in a regio- and chemoselective manner: the competing epoxidation of a C-C double bond does not occur.

Oxidation of Alcohols, Sulfur, and Phosphorus Compounds as well as Si-Si and Si-H Bonds.

Bis(trimethylsilyl) peroxide acts as an effective oxidant for alcohols in the presence of Pyridinium Dichromate or RuCl2(PPh3)3 complex as the catalyst in CH2Cl2.13 By this method, primary allylic and benzylic alcohols can be selectively oxidized to a-enals in the presence of a secondary alcohol.

Sulfur Trioxide reacts with (1) in CH2Cl2 at -30 °C, affording Bis(trimethylsilyl) Monoperoxysulfate, an oxidant useful for the Baeyer-Villiger oxidation.14 In addition, sulfides can be converted to sulfoxides or sulfones by use of (1) in benzene at reflux.1b,15,16 This peroxide can also oxidize phosphines and phosphites to the corresponding oxyphosphoryl derivatives with retention of configuration at the phosphorus center in high yields.1b,17 Furthermore, it converts the P=S and P=Se functionalities to the P=O group with inversion of configuration at the phosphorus center.17 The CF3SO3SiMe3 or Nafion-SiMe3 catalyzed oxidation of nucleoside phosphites to phosphates under nonaqueous conditions is applied to the solid-phase synthesis of oligonucleotides.18,19

Reactions between (1) and disilanes containing fluorine atoms or possessing ring strain proceed readily at ambient temperature to generate the corresponding disiloxanes.20 Oxidation of hydrosilanes (R3SiH) with (1) gives a mixture of R3SiOH and R3SiOSiMe3. The ratio of R3SiOH to R3SiOSiMe3 tends to decrease in the order Et3SiH > PhMe2SiH > Me3SiSiHMe2.

Isomerization of Allylic Alcohols and Formation of 1-Halo-1-alkynes.

Isomerization of primary and secondary allylic alcohols to tertiary isomers proceeds in CH2Cl2 at 25 °C in the presence of a catalyst that is prepared in situ by activation of Vanadyl Bis(acetylacetonate) or MoO2(acac)2 with (1) (eq 3).21 On the other hand, terminal alkynes react with (1) in the presence of copper or zinc halides in THF at -15 °C to afford terminal 1-halo-1-alkynes in 40-85% yields.22 By the same method, 1-cyano-1-alkynes are obtained in 65% yield by use of copper cyanide.

Related Reagents.

Bis(trimethylsilyl) Peroxide-Vanadyl Bis(acetylacetonate).

1. (a) Brandes, D.; Blaschette, A. JOM 1973, 49, C6. (b) Brandes, D.; Blaschette, A. JOM 1974, 73, 217. (c) Alexandrov, Y. A. JOM 1982, 238, 1. (d) Huang, L.; Hiyama, T. Yuki Gosei Kagaku Kyokaishi 1990, 48, 1004 (CA 1991, 114, 102 079x).
2. Suzuki, M.; Takada, H.; Noyori, R. JOC 1982, 47, 902.
3. Taddei, M.; Ricci, A. S 1986, 633.
4. Camici, L.; Dembech, P.; Ricci, A.; Seconi, G.; Taddei, M. T 1988, 44, 4197.
5. Camici, L.; Ricci, A.; Taddei, M. TL 1986, 27, 5155.
6. Davis, F. A.; Lal, G. S.; Wei, J. TL 1988, 29, 4269.
7. Matsubara, S.; Takai, K.; Nozaki, H. BCJ 1983, 56, 2029.
8. Babin, P.; Bennetau, B.; Dunogues, J. SC 1992, 22, 2849.
9. Jackson, W. P. SL 1990, 9, 536.
10. Olah, G. A.; Ernst, T. D. JOC 1989, 54, 1204.
11. Pohmakotr, M.; Winotai, C. SC 1988, 18, 2141.
12. Hwu, J. R. JOC 1983, 48, 4432.
13. Kanemoto, S.; Matsubara, S.; Takai, K.; Oshima, K.; Utimoto, K.; Nozaki, H. BCJ 1988, 61, 3607.
14. Adam, W.; Rodriguez, A. JOC 1979, 44, 4969.
15. Kocienski, P.; Todd. M. CC 1982, 1078.
16. Curci, R.; Mello, R.; Troisi, L. T 1986, 42, 877.
17. Kowalski, J.; Wozniak, L.; Chojnowski, J. PS 1987, 30, 125.
18. Hayakawa, Y.; Uchiyama, M.; Noyori, R. TL 1986, 27, 4191.
19. Hayakawa, Y.; Uchiyama, M.; Noyori, R. TL 1986, 27, 4195.
20. Tamao, K.; Kumada, M.; Takahashi, T. JOM 1975, 94, 367.
21. Matsubara, S.; Okazoe, T.; Oshima, K.; Takai, K.; Nozaki, H. BCJ 1985, 58, 844.
22. Casarini, A.; Dembech, P.; Reginato, G.; Ricci, A.; Seconi, G. TL 1991, 32, 2169.

Jih Ru Hwu & Buh-Luen Chen

Academia Sinica & National Tsing Hua University, Taiwan, Republic of China

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