Efficient synthesis of o-alkynyl-N-pivaloylanilines from o-acyl-N-pivaloylanilines and lithium trimethylsilyldiazomethane

Reaction of o-acyl-N-pivaloylanilines with lithium trimethylsilyldiazomethane efficiently gave the corresponding o-alkynyl-N-pivaloylanilines via alkylidenecarbene intermediates.     

Facile synthesis of 3-trimethylsilylindazoles by [3+2]cycloaddition reaction of lithium trimethylsilyldiazomethane with benzynes

[3+2]Cycloaddition reaction of lithium trimethylsilyldiazomethane with benzynes, generated from halobenzenes, gave the corresponding 3-trimethylsilylindazoles in good to moderate yields.     

Facile synthesis of 2-unsubstituted benzofuran-3-carboxylates using diazo(trimethylsilyl)methylmagnesium bromide

Diazo(trimethylsilyl)methylmagnesium bromide reacted with (o-methoxyphenyl)(oxo)acetates to readily afford 2-unsubstituted benzofuran-3-carboxylates via oxonium ylides formed from the initially generated alkylidenecarbene intermediates.     

Trimethylsilyldiazomethane – A Mild and Efficient Reagent for the Methylation of Carboxylic Acids and Alcohols in Natural Products

Summary. Esterification of various naturally occurring carboxylic acids with trimethylsilyldiazomethane proceeds nearly quantitatively under very mild conditions. Furthermore, highly sterically hindered alcohols can be converted directly to the corresponding methyl ethers. Improved methods for the preparation and quantification of this reagent are described.     

Optimized derivatization of acidic herbicides with trimethylsilyldiazomethane for GC analysis

In the present study, the preparation of methyl esters of chlorophenoxy acids with trimethylsilyldiazomethane (TMSD) is reported. TMSD is a mild and safe alternative to the highly toxic, thermally labile, and explosive diazomethane. Due to the novelty of this method, the characteristics of the reaction were investigated and the derivatization procedure was screened for statistically significant factors. The parameters identified as influential are the amount of methanol as well as reaction time and temperature. A careful optimization by a complete factorial response surface design was carried out to generate optimal reaction conditions with respect to maximum recovery and reaction yield. Special emphasis has been given to an accurate validation of the derivatization procedure. LODs were determined between 4.1 and 8.1 ng/mL for the enriched sample and linearity was proofed for more than five orders of magnitude. The applicability of the method was demonstrated by the analyses of quality control material including sample preparation with SPE. Polar herbicides investigated in the study belong to acetic acid (2,4-D, MCPA, and 2,4,5-T), butanoic acid (MCPB), and propanoic acid (mecoprop). An efficient, fast, and high-throughput method for the determination of polar herbicides including the potential for automation is proposed.     

Stereoselective synthesis of ambiphilic alkenes via regioselective methylation of α-trifluoromethanesulfonyl carbonyl compounds with trimethylsilyldiazomethane

α-Trifluoromethanesulfonyl esters, ketones and amides are C-H acids capable of reacting with trimethylsilyldiazomethane to afford the corresponding ambiphilic alkenes. While esters were found to be non-selective, ketones were highly regioselective for O-methylation and displayed variable E/Z stereoselectivity. Amides were observed to be both highly regio- and stereoselective, affording O-methylation with exclusive formation of the Z-alkene.     

New synthesis of 3-substituted indoles using lithium trimethylsilyldiazomethane

Lithium trimethylsilyldiazomethane smoothly reacted with N-tosyl-o-acylanilines to give 3-substituted indoles in good to high yields.     

One-pot, cis-selective synthesis of α-substituted β-trimethylsilyl-α,β-epoxyesters from α-ketoesters and diazo(trimethylsilyl)methyl magnesium bromide

Reaction of α-ketoesters with diazo(trimethylsilyl)methyl magnesium bromide followed by in situ treatment with pivalic acid gave α-substituted β-trimethylsilyl-α,β-epoxyesters in an efficient and cis-selective manner.     

Thermally assisted methylation and subsequent silylation of scheduled acids of chemical weapon convention for on-site analysis and its comparison with the other methods of methylation

On-site verification of the chemical weapon convention (CWC) requires provision for the detection and identification of alkyl phosphonic acids as well as some organic acids that are amenable to GC-MS only after derivatisation. Various derivatisation methods have been used for the identification of these acids and for many cases the methyl derivatives are less prone to artifacts possibly leading to false positive identification. Methylation with diazomethane is widely used but, especially for on-site analysis it has limitation due to the potential explosive and health hazards. Other methylation procedures like trimethylsilyldiazomethane (TMSD), thermally assisted methylation (TAM) by trimethylphenylammonium hydroxide (TMPAH) and trimethylsulfonium hydroxide (TMSH) are evaluated. Data for methylation for the alkyl alkylphosphonic acids, alkylphosphonic acids and benzilic acid are reported. In addition, TAM followed by the silylation in the same sample without any additional sample preparation is also reported. Several parameters such as solvent, temperature, amount of reagents, time, etc. were studied. The two commercially available reagents namely, TMPAH and TMSH for TAM and subsequent silylation were evaluated. The LOD with TMPAH was below 0.5 ng per injection since all of the acids were detected by GC-MS with the S/N of >3 in full scan mode by AMDIS and their inter day relative standard deviation was from 4.7% to 10.8%.     

New synthesis of t-butyl arylpropiolates using diazo(trimethylsilyl)methylmagnesium bromide

Diazo(trimethylsilyl)methylmagnesium bromide smoothly reacted with t-butyl aryl(oxo)acetates to afford the corresponding arylpropiolates via alkylidenecarbene intermediates. In this reaction system, the magnesium bromide salt of trimethylsilyldiazomethane was significantly efficient compared to the lithium one, commonly known as a reagent for the conversion of aldehydes and aryl ketones into acetylenes.