2.2- Dichloro-acetic acid methyl ester

The pyrimidine part (4,5-dichloro-6-methylpyrimidine, 11) is synthesized in a two-step sequence starting with the condensation of 2-chloro-3-oxobutanoic acid methyl ester (8) and formamidine acetate 9 [15] to give 5-chloro-4-hydroxy-6-methylpyrimidine (10) in high yield, followed by the chlorination of the hydroxy group using standard synthesis methodology [15-18]. Synthesis of the sub-... 

Dichloro-phenoxy acetic acid, 2,4,5- trichlorophenoxy acetic acid Herbicide derivatised to its methyl or 2-chlororethyl ester, then gas chromatography. 70 - 74% recovery [169]... 

Compound 85 was dehydrogenated at 300° over palladium black under reduced pressure to a pyridine derivative 96 which was independently synthesized by the following route. Anisaldehyde (86) was treated with iodine monochloride in acetic acid to give the 3-iodo derivative 87. The Ullmann reaction of 87 in the presence of copper bronze afforded biphenyldialdehyde (88). The Knoevenagel condensation with malonic acid yielded the unsaturated diacid 91. The methyl ester (92) was also prepared alternatively by a condensation of 3-iodoanisaldehyde with malonic acid to give the iodo-cinnamic acid (89), followed by the Ullmann reaction of its methyl ester (90). The cinnamic diester was catalytically hydrogenated and reduced with lithium aluminium hydride to the diol 94. Reaction with phosphoryl chloride afforded an amorphous dichloro derivative (95) which was condensed with 2,6-lutidine in liquid ammonia in the presence of potassium amide to yield pyridine the derivative 96 in 27% yield (53). 

Selective acylation occurs at C-6 of methyl e<-D-glucopyranoside on treatment with hexachloro- or pentachloro-propanone to yield tri-chloro- or dichloro-acetates respectively. The chlorinated ester group is easily removed by ammonia in ether and thus constitutes a base-labile complement to the acid-labile trityl function (Scheme 3). Trifluoroacetylation of carbohydrates for g.c. analysis has... 

The plasma samples were purified on an anion exchange resin MCI GEL CA08P (170 X 10 mm. Cl ). DL-Pantothenic acid and DL-hopantenic acid were eluted with 1 M NaCl solution and free acids were extracted with ethyl acetate from the eluate acidified with 6 M HCl in the presence of ammonium sulfate and esterified with 1.5 M HCl in methanol at room temperature for 1 h. The resulting methyl esters were trifluoroacetylated with trifluoroacetic anhydride in dichloro-methane at room temperature for 30 min and analyzed by GC-MF. Mass spectrometry with selected-ion monitoring was employed for the simultaneous determination of the enantiomers of pantothenic acid and hopanthenic acid. The stable mass fragments were detected at m/z 257 and 271, being the base peaks of pantothenic acid and hopantenic acid, respectively (Fig. 31). 

Notable examples of general synthetic procedures in Volume 47 include the synthesis of aromatic aldehydes (from dichloro-methyl methyl ether), aliphatic aldehydes (from alkyl halides and trimethylamine oxide and by oxidation of alcohols using dimethyl sulfoxide, dicyclohexylcarbodiimide, and pyridinum trifluoro-acetate the latter method is particularly useful since the conditions are so mild), carbethoxycycloalkanones (from sodium hydride, diethyl carbonate, and the cycloalkanone), m-dialkylbenzenes (from the />-isomer by isomerization with hydrogen fluoride and boron trifluoride), and the deamination of amines (by conversion to the nitrosoamide and thermolysis to the ester). Other general methods are represented by the synthesis of 1 J-difluoroolefins (from sodium chlorodifluoroacetate, triphenyl phosphine, and an aldehyde or ketone), the nitration of aromatic rings (with ni-tronium tetrafluoroborate), the reductive methylation of aromatic nitro compounds (with formaldehyde and hydrogen), the synthesis of dialkyl ketones (from carboxylic acids and iron powder), and the preparation of 1-substituted cyclopropanols (from the condensation of a 1,3-dichloro-2-propanol derivative and ethyl-... 

For the synthesis of permethric acid esters 16 from l,l-dichloro-4-methyl-l,3-pentadiene and of chrysanthemic acid esters from 2,5-dimethyl-2,4-hexadienes, it seems that the yields are less sensitive to the choice of the catalyst 72 77). It is evident, however, that Rh2(OOCCF3)4 is again less efficient than other rhodium acetates. The influence of the alkyl group of the diazoacetate on the yields is only marginal for the chrysanthemic acid esters, but the yield of permethric acid esters 16 varies in a catalyst-dependent non-predictable way when methyl, ethyl, n-butyl or f-butyl diazoacetate are used77). 

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