Trimethylsilyldiazomethane

Trimethylsilyldiazomethane is the organosilicon compound with the formula (CH3)3SiCHN2. It is classified as a diazo compound. Trimethylsilyldiazomethane is a commercially available reagent used in organic chemistry as a methylating agent and as a source of CH2 group. Its behavior is akin to the less convenient reagent diazomethane.[3]

Trimethylsilyldiazomethane
Names
IUPAC name
(Diazomethyl)trimethylsilane
Other names
Trimethylsilyldiazomethane
Diazo(trimethylsilyl)methane
Identifiers
3D model (JSmol)
1902903
ChemSpider
ECHA InfoCard 100.131.243
MeSH Trimethylsilyldiazomethane
UNII
Properties
C4H10N2Si
Molar mass 114.223 g·mol−1
Appearance greenish-yellow liquid[1][2]
Boiling point 96.0[1] °C (204.8 °F; 369.1 K)
Hazards
Safety data sheet External MSDS
Xn F N
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Infobox references

Preparation

Trimethylsilyldiazomethane may be prepared by treating (trimethylsilyl)methylmagnesium chloride with diphenyl phosphorazidate.[4]

Uses

It is a less explosive alternative to diazomethane for the methylation of carboxylic acids. It also reacts with alcohols to give methyl ethers, where diazomethane may not.[5]

It has also been employed widely in tandem with GC-MS for the analysis of various carboxylic compounds which are ubiquitous in nature. The fact that the reaction is rapid and occurs readily makes it attractive. However, it can form artifacts which complicate spectral interpretation. Such artifacts are usually the trimethylsilylmethyl esters, RCO2CH2SiMe3, formed when insufficient methanol is present. Acid-catalysed methanolysis is necessary to achieve near-quantitative yields of the desired methyl esters, RCO2Me.[6]

The compound is a reagent in the Doyle-Kirmse reaction with allyl sulfides and allyl amines.

Trimethylsilyldiazomethyllithium

Trimethylsilyldiazomethane is deprotonated by butyllithium:

(CH3)3SiCHN2 + BuLi → (CH3)3SiCLiN2 + BuH

The lithio compound is versatile. From it can be prepared other trimethylsilyldiazoalkanes:

(CH3)3SiCLiN2 + RX → (CH3)3SiCRN2 + LiX

(CH3)3SiCLiN2 reacts with ketones and aldehydes to give, depending on the substituents, acetylenes.[7]

Safety

Trimethylsilyldiazomethane is highly toxic. It has been implicated in the death of at least two chemists, a pharmaceutical worker in Windsor, Nova Scotia, Canada and one in New Jersey.[8][9][10] Inhalation of diazomethane is known to cause pulmonary edema; trimethylsilyldiazomethane is suspected to behave similarly.[11]

When used as a reagent in organic synthesis to convert carboxylic acids to their methyl esters, trimethylsilyldiazomethane undergoes acid-catalysed methanolysis, forming diazomethane in situ.[6] A similar hydrolysis reaction may take place when trimethylsilyldiazomethane comes into contact with water on the surface of a human lung.[11]

Trimethylsilyldiazomethane is nonexplosive.[4]

References
  1. Seyferth, Dietmar.; Dow, Alan W.; Menzel, Horst.; Flood, Thomas C. (1968). "Trimethylsilyldiazomethane and trimethylsilylcarbene". J. Am. Chem. Soc. 90 (4): 1080–1082. doi:10.1021/ja01006a055.
  2. Seyferth, Dietmar; Menzel, Horst; Dow, Alan W.; Flood, Thomas C. (1972). "Trimethylsilyl-substituted diazoalkanes I. Trimethylsilyldiazomethane". J. Organomet. Chem. 44 (2): 279–290. doi:10.1016/S0022-328X(00)82916-2.
  3. Shioiri, Takayuki; Aoyama, Toyohiko; Snowden, Timothy (2001). "Trimethylsilyldiazomethane". e-EROS Encyclopedia of Reagents for Organic Synthesis. doi:10.1002/047084289X.rt298.pub2.CS1 maint: uses authors parameter (link)
  4. Takayuki Shioiri, Toyohiko Aoyama, and Shigehiro Mori (1993). "Diazo(trimethylsilyl)methane". Organic Syntheses.CS1 maint: multiple names: authors list (link); Collective Volume, 8, p. 612
  5. Armin Presser & Antje Hüfner (2004). "Diazo(trimethylsilyl)methane – A Mild and Efficient Reagent for the Methylation of Carboxylic Acids and Alcohols in Natural Products". Chemical Monthly. 135 (8). doi:10.1007/s00706-004-0188-4.
  6. Kühnel, E.; Laffan, D. D. P.; Lloyd-Jones, G. C.; Martínez del Campo, T.; Shepperson, I. R.; Slaughter, J. L. (2007). "Mechanism of Methyl Esterification of Carboxylic Acids by Trimethylsilyldiazomethane". Angew. Chem. Int. Ed. 46 (37): 7075–7078. doi:10.1002/anie.200702131.
  7. Moody, Christopher J.; Shioiri, Takayuki; Aoyama, Toyohiko (2011). "Diazo(trimethylsilyl)methyllithium". e-EROS Encyclopedia of Reagents for Organic Synthesis. pp. 1–7. doi:10.1002/047084289X.rd019.pub2.CS1 maint: multiple names: authors list (link)
  8. Family says N.S. pharmaceutical worker named chemical he used before death, The Amherst Daily News, October 20, 2008
  9. N.S. probe into pharma worker's death finds vent hoods turned off in lab, canadaeast.com, May 13th, 2009
  10. "OSHA accident report regarding a trimethylsilyldiazomethane fatality". https://www.osha.gov/. Retrieved 10 April 2020. External link in |website= (help)
  11. Murphy, N. G.; Varney, S. M.; Tallon, J. M.; Thompson, J. R.; Blanc, P. D. (2009). "Fatal Occupational Exposure to Trimethylsilyl-Diazomethane". Clin. Toxicol. 47 (7): 712. doi:10.1080/15563650903076924.
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