Diazomethane esterification

Transformations of Methyl 5-0-Benzyl-2-0-methyl-/3-I)-glueofuranosidurono-6,3-lae-tone (86) to Dimethyl (Z,E)-2-Methoxy-5-(phenylmethoxy)-2,4-hexadienedioatevl (87). ( Elimination employing DBU b oxidation with silver oxide-sodium hydroxide followed by diazomethane esterification c acidic glycoside cleavage, oxidation by dimethyl sulfoxide-acetic anhydride with formation of 5-0-benzyl-2-0-methyI-D-glucaro-1,4 6,3-dilactone, elimination by using DBU, followed by short treatment with diazomethane d elimination by DBU with subsequent diazomethane esterification e sodium borohydride in hexamethylphosphoric triamide 1 catalytic oxidation followed by short treatment with diazomethane " dimethyl sulfoxide-sulfur trioxide-pyridine-triethylamine.150)... 

No yield provided product taken directly to a diazomethane esterification. Overall yield OK. 

Preparation of the left-hand fragment, which incorporates the C-11 to C-13 portion of 18, utilizes the aldol reaction of / -boron enolate 10 with propionaldehyde to provide the a-hydroxy acid 11 in 85% yield and 100 1 stereoselectivity. Subsequent diazomethane esterification, O-silylations, DIBAL reduction, and Collins oxidation affords the optically pure aldehyde 12 in an overall yield of 75%. 

To extend this strategy to MIPs a well-studied MIP system was used to generate the racemic MIP starting material [12,15,16]. Racemic PAA was imprinted in the standard MAA/EGDMA matrix. This racemic MIP was equilibrated with enantiomerically pure L-PAA and then treated with diazomethane. Esterification presumably reacts with the unprotected D-selective sites. Verification of the enantioselectivity in the modified polymer was carried out using batch rebinding studies (Scheme 10). The polymer was equilibrated with racemic PAA. The observation of enantiomeric excess in the free solution confirms the enantioselectivity of the modified polymer. 

Although it is seldom used, esterification of pyrimidinecarboxylic acids proceeds normally. Conditions are illustrated by the conversion of pyrimidine-4-carboxylic acid (181 R = H) into its methyl ester (181 R = Me) by methanol/sulfuric acid (47%), methanol/hydrogen chloride (80%), or by diazomethane (ca. 100%) (60MI21300). The isomeric methyl pyrimidine-2-carboxylate is formed by treatment of the silver salt of the acid with methyl iodide. Higher esters, e.g. (182 R = Bu), are usually made by warming the acid (182 R = H) with the appropriate alcohol and sulfuric acid (60JOC1950). 

The preparation of several medium- and large-sized 2-carbo-methoxycycloalkanones has been accomplished by treatment of the cycloalkanone with sodium triphenylmethyl, followed by carbonation with dry ice, and esterification with diazomethane. 1 The yields are good but the procedure is laborious. The synthesis of 2-carbomethoxycycIooctanone via the Dieckmann cyclization of dimethyl azelate with sodium hydride yields 48% of this product when the procedure is carried out over a 9-day period.3... 

Schemes 15 and 16 summarize the syntheses of intermediates that represent rings A and D of vitamin Bi2 by the Eschenmoser group. Treatment of lactam/lactone 51, the precursor to B-ring intermediate 8 (whose synthesis has already been described, see Scheme 8), with potassium cyanide in methanol induces cleavage of the y-lac-tone ring and furnishes intermediate 76 after esterification of the newly formed acetic acid chain with diazomethane. Intermediate 76 is produced as a mixture of diastereomers, epimeric at the newly formed stereocenter, in a yield exceeding 95%. Selective conversion of the lactam carbonyl in 76 into the corresponding thiolactam...

Although the biosynthetic cascade hypothesis predicts the co-occurrence of endiandric acids D (4) and A (1) in nature, the former compound was not isolated until after its total synthesis was completed in the laboratory (see Scheme 6). Our journey to endiandric acid D (4) commences with the desilylation of key intermediate 22 to give alcohol 31 in 95% yield. The endo side chain is then converted to a methyl ester by hydrolysis of the nitrile to the corresponding acid with basic hydrogen peroxide, followed by esterification with diazomethane to afford intermediate 32 in 92% overall yield. The exo side chain is then constructed by sequential bromination, cyanide displacement, ester hydrolysis (33), reduction, and olefination (4) in a straight-... 

Other important porphyrins which can be derived from hemin are hematoporphyrin (5) and mesoporphyrin (6). Hematoporphyrin (5) which is commercially available at a relatively low price is sensitive towards acid due to the 1-hydroxyethyl groups, so commercial samples contain only 60 to 70% of hematoporphyrin. Pure hematoporphyrin dimethyl ester which is a racemic and diastereomeric mixture of four stereoisomers can be obtained by esterification with diazomethane and subsequent chromatography on neutral alumina.84 The pure stereoisomers can be prepared by enantioselective reduction of diacetyldeuteroporphyrin dimethyl ester.85a b The... 

The only other esterification method which rivals the present procedure in convenience, mildness of conditions, selectivity, and yield js the preparation of methyl esters wdth diazomethane [Methane, diazo-] 10 Esterification with trialkyloxonium salts, however, allows... 

As sulfonic acid cannot be vaporized, its determination by the direct gas chromatography (GC) method is not possible. To enable determination by GC, the reactivity of the S03H group is used the esterification of the S03H group with diazomethane via acid chloride is one way to transfer the sulfonic acid to volatile compounds. By conversion of the sulfonic acid with phosphoric acid at 200-210°C, the S03H group is cleaved and the hydrocarbons are obtained [184-186]. 

Although it is unlikely that the tetrahydrofuran ring would open under these conditions of polymerization, the polymer was hydrolyzed in 0.2 M sodium hydroxide solution, in order to confirm its structure. Clear colorless liquid was obtained after acidification followed by esterification with diazomethane. Its IR and NMR data compares exactly to that obtained from 59 which was prepared from the neutral hydrolysis of 57 and esterification of the resultant acid with diazomethane. Since the apparent sole product obtained from hydrolysis of the polymer was 59, they conclude that 58 represents the correct structure for this polymer. 

The scope of the multi-residue method is extended permanently by testing and then including further active substances that can be determined by GC. Acidic analytes (such as phenoxyacetic acids or RCOOH metabolites) are included into the homogeneous partitioning by acidifying the raw extracts to a pH below the pKs value of the carboxylic acids. To include these analytes in the GC determination scheme they have to be derivatized with diazomethane, diazoethane, trimethylsilyldiazomethane, acidic esterification or benzylation, or by silanizing the COOH moiety. 

Two methods for converting carboxylic acids to esters fall into the mechanistic group under discussion the reaction of carboxylic acids with diazo compounds, especially diazomethane and alkylation of carboxylate anions by halides or sulfonates. The esterification of carboxylic acids with diazomethane is a very fast and clean reaction.41 The alkylating agent is the extremely reactive methyldiazonium ion, which is generated by proton transfer from the carboxylic acid to diazomethane. The collapse of the resulting ion pair with loss of nitrogen is extremely rapid. 

Modifications at the carboxyl group include reduction (with dibor-ane260 or borohydride, after activation with soluble carbodiimide261,262), esterification (with diazomethane,101,223,283,264 or acyl or aryl chlorides224,264), and formation of amide esters.263,265... 

The photochemical fragmentation of vinyl-substituted 1,2k5-oxaphosphetanes, representing a step of a photochemical variant of the Wittig reaction with methyl-eneoxophosphoranes, has been examined as a model in the case of 22b20). Photolysis of this compound in methanol affords the 1,3-diene 24b as well as the highly reactive dioxophosphorane 23 which is trapped by the solvent subsequent esterification of the half-ester 62, formed as a primary product, with diazomethane to give the diester 63 was undertaken solely for preparative reasons 20). 

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