Diazomethane trimethylsilyl

The desilylacetylated qrcloadducts, produced from the reactions of trimethylsilyl-diazomethane with 3-crotonoyl-2-oxazolidinone or 3-crotonoyl-4,4-dimethyl-2-oxa-zolidinone, were transformed to methyl traws-l-acetyl-4-methyl-l-pyrazoline-5-car-boxylate through the reactions with dimethoxymagnesium at -20 °C. When the optical rotations and chiral HPLC data were compared between these two esters, it was found that these two products had opposite absolute stereochemistry (Scheme 7.39). The absolute configuration was identified on the basis of the X-ray-determined structure of the major diastereomer of cycloadduct derived from the reaction of trimethylsilyldiazomethane to (S)-3-crotonoyl-4-methyl-2-oxazolidi-none. 

Some other groups have studied the opportimity to enhance the diastere-oselectivity of the transformation using the usual copper-bis(oxazohne) catalysts but modifying the carbene source. France et al. [25] observed that the use of (trimethylsilyl)diazomethane associated with a bis(oxazoline) and [Cu(CH3CN)4]PF6 as catalyst precursor allowed the formation of the trans isomer with high yield and selectivity, probably due to the steric bulk of the trimethylsilyl group. 

In 1994, only 15% of EPA method validations (tolerance method validation and environmental chemistry method validations) that involved GC were carried out using GC/MS. In 2002, this number is reversed in that 85% of the GC methods that were validated by both programs used GC/MS. Many of the compounds investigated in these method trials were polar compounds, and hence these compounds required derivatization in order to be amenable to GC. One common methylating agent is (trimethylsilyl)diazomethane, which is used, for example, to methylate the sulfonamide flumetsulam. As opposed to HPLC/MS, where derivatization is often not necessary, the GC/MS procedure involves an extra step to methylate this compound, under dry conditions, prior to determination by GC/MS. 

After recovering fluthiacet-methyl from the crop extract with n-hexane, acidify the residual aqueous layer and extract the free form of fluthiacet-methyl with n-hexane-ethyl acetate (2 1, v/v). After evaporating the solvent, clean up the residue with an Ci8 Empore Disk Cartridge. After methylation of the free form with trimethylsilyl-diazomethane, clean up the ester with a Bond Elut LRC SI and a Sep-Pak Plus NH2 cartridge, and quantify as fluthiacet-methyl by GC/FTD. 

More recently, [2+3] cycloaddition reaction of the tri-te/t-butylphenylphosphaethyne (25) has been reinvestigated, when in spite of the steric encumbrance of extremely bulky Mes group, the use of trimethylsilylated diazomethane (24) makes its cycloaddition successful, which is followed by SiMe3/H migration yielding bulky [l,2,4]diazaphospholes [33], Phosphaalkyne 25 reacts with 24 in a regioselective manner to form intermediate cycloadduct 26, which undergoes facile aromatization... 

In contrast to A5-phosphorus-substituted diazo derivatives, which have been known for a long time,22 the synthesis of the first o -diazophosphine was reported as recently as 1985.23 This compound, namely the [bis(diiso-propylamino)phosphino](trimethylsilyl)diazomethane la, was obtained by treatment of the lithium salt of trimethylsilyldiazomethane with 1 equiv of bis(diisopropylamino)chlorophosphine. 

An exchange reaction occurs when nitrosylchloride is reacted with (phos-phino)(trimethylsilyl)diazomethane la to yield an unstable ce-nitroso a-phosphinodiazo derivative lq and chlorotrimethylsilane.75 Spontaneous loss of N2 leads to the transient (nitroso)(phosphino)carbene 2q, which can also be regarded as the phosphorus vinyl ylide 2q or even better as the A3-... 

A very similar reaction to that of Pechmann and Nold but which probably does not proceed through a dipolar cycloaddition manifold is the formation of 1,2,3-thiadiazole (6) via a thionoester and lithium trimethylsilyldiazomethane (Equation (17)) <86H(24)589>. Lithium trimethylsilyl-diazomethane also reacts with thioketones to produce 1,2,3-thiadiazoles <87H(26)1467>. 

Diazomethylene)phosphoranes 33 (Scheme 8.10), which represent another type of diazocumulenes (12) are easily obtained by the oxidative ylidation of the corresponding phosphanyl(trimethylsilyl)diazomethane with CCI4. The increased stability of these compounds as compared with diazocumulenes (R2C=C=N2) is probably due to the ylidic character of the P=C bond. These diazo compounds exhibit the expected dipolar reactivity toward electron-deficient alkenes, alkynes, phosphaalkenes, and heterocumulenes (12). Thus, 33 reacts with TCNE to form A -pyrazoline 35 (60). Furthermore, 33 could be converted into the phosphonio-borate-substituted diazo compound 34, which underwent subsequent cycloaddition with electron-deficient alkenes (e.g., 34 36) (61). 

To quantify the amount of carboxylic acid in the side chain of the step 2 product, the material was methyl esterified using trimethylsilyl diazomethane. 

Polyauration starts from the carbon atom for which the species with four, five and six gold atoms have been prepared. These are available from the reaction of polyborylmethanes with [AuCl(PR3)] or trimethylsilyl diazomethanes with [0(AuPR3)3]+. The tetranuclear derivatives are formed with bulky phosphines and less sterically demanding phosphines enable the synthesis of the hypervalent species [230]. The structures of these complexes are tetrahedral, trigonal bypiramidal and octahedral, respectively (Figure 1.36). Many complexes of the type [RC(AuPR3)4]+ [231] have also been synthesized. 

Diazocarbonyl compounds can also be prepared by C-acylation of diazoalkanes with polystyrene-bound acyl halides (Entry 6, Table 10.19). As an alternative to diazomethane, the more stable a-(trimethylsilyl)diazomethane may be used, which is sufficiently nucleophilic to react with acyl halides. On heating, the resulting a-(trimethyl-silyl)diazo ketones undergo Wolff rearrangement to yield ketenes, and have also been used as starting materials for the preparation of oxazoles [368]. 

When phenyl(trimethylsilyl)diazomethane (20) is pyrolyzed in the gas phase, typical reactions of carbene 21 can be observed (see Section III.E.4). However, copyrolysis with alcohols or carbonyl compounds generates again products which are derived from silene 2239,40 (equation 6). Thus, alkoxysilanes 23 are obtained in the presence of alcohols and alkenes 24 in the presence of an aldehyde or a ketone. 2,3-Dimethylbuta-l,3-diene traps both the carbene (see Section ni.E.4) and the silene. 

Bis(trimethylsilyl)diazomethane (25) represents an excellent source for silene 2641. It appears that carbene 3c, which is expected from the photochemical or thermal decomposition of 25, escapes most trapping efforts due to rapid isomerization to silene 26 (equation 7). Photolysis of 25 in benzene solution yields 27 and 28 in a combined yield of 64% and disilazane 29 (10%) all these products are likely to be derived from 26. Similarly, photolysis in the presence of methanol or I)20 traps the silene quantitatively (to give 31 and 32). 

It should be mentioned that alkenes 236, which are often found as (formal) carbene dimers in reactions involving electrophilic carbenes, have never been observed in the context of phosphino(silyl)carbenes. UV-irradiation of a [bis(dialkylamino)phosphino] (trimethylsilyl)diazomethane leads to a l(A5),3(k5)-diphosphete 237 (equation 80) which can be regarded as the head-to-tail cyclodimer of a phosphavinyl ylide (cf 232B), whereas irradiation of diphenylphosphino- or dunethoxyphosphino-(trimethylsilyl)diazomethane produces a l,2(k5),4(k5),6(X5)-azatriphosphorin 238 in a sequence which may also include the corresponding diphosphete 237138. 

The thus formed heterocycles 412a decompose or isomerize thermally the required reaction temperature depends on the substituents. The isomerization leads to diazomethane derivatives 413a, whereas the decomposition by [2 + 3] cycloreversion reaction gives bis(trimethylsilyl)diazomethane and short-lived silanimines 414a, which dimerize in most cases. The ratio isomerization/cycloreversion depends on R, the solvent and the temperature and more cycloreversion is observed at higher temperature. An unfavourable side reaction is the insertion of Me2Si=NR into Si—N bonds (formation of 415a and 686 see below). 

A much more general method for acyl silane synthesis involving silyl diazo intermediates is illustrated in Scheme 1688. The lithiated derivative of trimethylsilyl diazomethane reacts smoothly with alkyl halides in THF solution to give a-trimethylsilyl diazoalkanes in good yields. Oxidative cleavage of the diazo moiety is effected using 3-chloroperbenzoic acid in benzene solution, to give access to a wide variety of acyl silanes in yields of up to 71%. A phosphate buffer (pH 7.6) is used to prevent side reactions. Aromatic acyl silanes clearly cannot be prepared by this chemistry since an aromatic nucleophilic substitution reaction would be required. 

The sodium anion of trimethylsilyl diazomethane has also been used to open W-acyl (3-lactams 114, Scheme 38. The resulting intermediate a-diazoketones... 

Aggarwal, V. K. Ferrara, M. Highly selective aziridination of imines using trimethylsilyl-diazomethane and applications of C-silylaziri-dines in synthesis. Org. Lett. 2000, 2, 4107-4110. 

Z)-l-Trimethylsilyl-l-alkenes.1 The a-trimethylsilyl diazoalkanes (2), prepared by reaction of primary halides (1) with the lithium anion of trimethylsilyl diazomethane, decompose on treatment with rhodium(II) pivalate [superior in this case to rhodium(II) acetate] to (Z)-l-trimethylsilyl-1-alkenes. 

Treatment of a nitrosourea with a base comprises the final step in a preparation of a diazomethane derivative. This has been successfully applied to the synthesis of trimethylsilyl diazomethane.243 244... 

J0rgensen and coworkers reported the preparation of A-tosyl aziridines 19-20 by the net carbene addition (via a diazo compound) to A-tosyl iminoesters with either copper or silver catalysts.13,14 It was noted that the copper catalysts were generally superior, although a catalyst derived from AgSbF6 and (R)-Tol-BINAP provided the corresponding aziridine 19 from 16 and trimethylsilyl diazomethane 17 (R = TMS) in excellent chemical yield with high levels of diastereoselectivity, but unfortunately the enantioselectivity was poor (Scheme 8.3). This success with trimethylsilyldiazo-... 

The deprotonation of (trimethylsilyl)diazomethane with n-butyllithium afforded the lithium silyldiazomethane 37, which reacts with CO at — 78 °C to give an acyllithium 3855,56. This intermediate underwent nitrogen extrusion generating the silylynolate 39 used as ketenylating reagent (Scheme 9). 

A dihydro-1,2,4-diazaphosphole is obtained by reaction of bis(tri-methylsilyl)amino-trimethylsilylmethylenephosphane with <-Bu-CHN2 resp. trimethylsilyl diazomethane in n-hexane at 0°C (65, 66). Correspondingly, one gets at room temperature the 4,5-dihydro-5,5-diphenyl-3,4-di(2,4,6-trimethyphenyl)-l,2,4-oxazaphosphol with mesityl nitriloxide and the phosphaalkene [Eq. (19)] (64). 

The reaction of a carboxylic acid with diazomethane is mild and efficient Diazomethane is usually prepared by reaction of potassium hydroxide with N-methyl-A/-nitroso-p-toluenesulfonamide (HAZARD carcinogenic) and used in ether solution since it is volatile, toxic, and explosive.44 Therefore, the method is most suitable for small scale reactions. A useful feature of the reaction is that diazomethane is intensely yellow and the consumption of the reagent is easily detected by the disappearance of the colour. It may be convenient to prepare the diazomethane in situ 45 (Trimethylsilyl)diazomethane is a safer alternative to diazomethane for the preparation of methyl esters and it is commercially available as a 2.0 M solution in hexanes,46 47... 

TMS production involves one specific functional group (-OH, -COOH, =NH, -NH2, or -SH), which loses an activated hydrogen and is replaced by a trimethylsilyl group (Proestos et ah, 2006). To achieve silylation, some authors have used BSTFA (N,0-hA(trimethyl-silyl)trifluoroacetamide) and TMCS (trimethylchlorosilane) successfully in several matrices (e.g. aromatic plants, cranberry fixiit) (Zuo et ah, 2002 Proestos et ah, 2006). Using silylated derivatives is advantageous for several reasons phenols and carboxylic acids are prone to silylation, these compounds can be derivatized in the same part of the process, and the minor products do not impede analysis and are well documented (Little, 1999 Stalikas, 2008). A two-step methylation procedure was used to analyze catechins and tannins in plant extracts. The first step used trimethylsilyl diazomethane (TMS-diazomethane) to pre-methylate the sample, and the second step used thermally assisted hydrolysis and methylation (THM). The pre-methylation step with TMS-diazomethane stabilized the dimer molecule m/z 540) by minimizing isomerization and reducing reactivity. (Shadkami et ah, 2009). 

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