Diazomethane method

For the esterification of difficultly accessible acids the elegant diazomethane method (p. 273) is most appropriate it usually proceeds very smoothly. 

Method A From X -phosphorins by oxidation with H2O2. Method B From 2-hydro-phosphinic-90 with diazomethane. Method C From l.l-dialkoxy-X -phosphorins with BBr3. Method D From pyrylium sMts with phenyl phosphine... 

The present procedure is a modification of earlier diazomethane methods and employs the relatively stable -tolylsulfonylmeth-ylnitrosamide. 

Dimethyl bromosuccinate was prepared from bromosuccinic acid by the diazomethane method (26) using the procedure of Eisenbraun, Morris, and Adolphen (27). It was distilled under vacuum (0.08-0.1 Torr) at 45°-49°C to yield a clear colorless oil. Thin layer chromatography with benzene as the solvent on SiC>2 yielded a symmetrical single spot, indicating either a pure compound or no separation with this particular solvent. Its mass spectrum had a very small peak corresponding to the parent compound, but none to a dibromo compound. The mass spectrum for dimethyl bromosuccinate was not found in the literature, but that for dimethyl succinate also has a small peak corresponding to the parent compound (25). 

One method that uses none of the above catalysis is worthy of mention, the diazomethane method. This method is very useful if there is only a very limited amount of free fatty acids as the starting material, since no extraction is needed before the resulting FAME can be injected into the GC for analysis. The authors of this unit have never performed this method. Interested readers can learn more from information presented elsewhere (Christie, 1989b). In addition, esters other than methyl may be required from time to time for specific purposes, and this is beyond the scope of the present discussion. 

Small quantities of cycloheptanone are prepared more conveniently by the diazomethane method 4 or by dry distillation of suberic acid salts 5-7 or suberic acid admixed with iron filings and barium hydroxide.8... 

GLC-FID/FPD and GC-MS Analysis of Oxidation Products. To obtain information regarding the molecular structure of the organic sulfur compounds present in samples, each of the soluble oxidation products were methylated using the diazomethane method and then analysed, initially by both dual FID/FPD gas chromatography, and by GC-MS. Representative FID and FPD traces obtained from the Herrin No. 6 samples are shown in Figures 2 and 3 respectively, while those for the Indiana No.5 samples are shown in Figures 4 and 5 respectively. 

HALOMETHYL DERIVATIVES OF SILICON, GERMANIUM, AND TIN BY THE DIAZOMETHANE METHOD... 

Germanium(IV) chloride, 2 109 Germanium compounds, halomethyl derivatives by the diazomethane method, 6 37, 39 nomenclature of, 2 265 5 64 organo-, 5 64... 

Halomethyl derivatives, of silicon, germanium, and tin by the diazomethane method, 6 37 Haloplumbic(IV) acids, H2PbXe, 1 48... 

See also Silicon tetrachloride) Silicon compounds, halomethyl derivatives by the diazomethane method, 6 37, 39 nomenclature of, 2 265 organo-, 3 50 nomenclature of, 3 55 Silicon tetraacetate, 4 45 Silicon tetrabromide, 1 38, 40 Silicon tetrachloride, 1 44 Silicon tetrafluoride, 4 145 Silicooxalic acid, (H Si, ,), formation of, by disilicon hexa-bromide, 2 101... 

Thorium oxybromide, 1 54 Tin, as reducing agent for complex tungsten(VI) chlorides in preparation of complex potassium chlorotungstates(III), 6 149 Tin compounds, halomethyl derivatives, by the diazomethane method, 6 37 (CH8) 2 (CH2C1) SnCl, 6 41 Tin (IV) iodide, 4 119 Titanium, powder by reduction of titanium (IV) oxide with calcium, 6 47... 

The diazomethane method is simple and usually no by-products are produced. The formation of polymethylene polymers, which is sometimes observed, can be avoided by using vessels with clean and smooth surfaces. Anhydrous conditions must be maintained during the reaction, as diazomethane decomposes on contact with water. The disadvantages of diazomethane are its toxicity and high reactivity, the latter often being the reason for explosions. Therefore, when working with diazomethane solution, it is better to prepare it freshly prior to use. If storage is necessary, it should be kept for only a short period at -20°C. 

BC13 in methanol. The method, for different modifications of the procedure, is comparable to the diazomethane method (see Table 4.2). 

Fischer esterification works well to prepare simple carboxylic esters. The diazomethane method would also react with the phenol, making the phenyl ether. 

Although these syntheses of deoxy ketoses have not been widely developed, the versatility of diazomethane as a synthetic reagent is amply demonstrated. In addition to heptuloses, the diazomethane method has been used for preparing various octuloses " and nonuloses. ... 

Occurrence and preparation. This nonulose was obtained from the ripe avocado (Calavo, Hass variety) by extraction and cellulose chromatography (see under D-g/ycero-D-ga/acto-heptose). It is also present in Sedum.2S2 Dried roots of Primula officinalis Jacq. provide another source of the nonulose256 (see under D-g/ycero-D-g/nco-heptose). The synthetic nonulose was prepared by the diazomethane method.291,292... 

Vorbeck et al. [173] compared the yields of the esterification reaction of organic acids with diazomethane and two reaction mixtures methanol—hydrochloric acid and methanol—boron trifluoride. The best results were achieved when the diazomethane method was used. 

From Diazo-compounds. The routine cuprous-catalysed diazomethane cyclo-propanation method has been used on bicyclic and bridged olefins. With fneso-tetraphenylporphin, this procedure gave a single cyclopropane product, unlike the corresponding reaction with diazo-esters. Trishomobenzene has been prepared by multiple use of this diazomethane method. It was shown to be the trans-isomer (78) by n.m.r. spectroscopy in (78) there are seven types of H whereas in its cis-isomer there would be only three. Twelve isomeric products have been isolated by preparative g.l.c. from the reaction of diazomethane-Cu2Cl2 with biallenyl (79). Some of the products could be synthesized independently, otherwise structural assignments were based upon spectroscopic evidence. 

The acid (67) has also been obtained from an intermediate in the synthesis of the ketone (53), the bicyclic acid (52). Compound (52) was converted by the diazomethane method into the corresponding bromoketone (62), the condensation of which with sodiomalonic ester and decarboxylation led to the keto acid (63). Cyclization of the latter under the action of sulfuric acid led to they-lactone (64), which has also been obtained by the lactonization of acid (67) [197, 198, 200]. All these methods have also been applied to the synthesis of the acid analogous to (67) not containing the 3-methoxy group [195, 201]. 

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