Methyl bromide, viii

For the synthesis of the AMT ester (VIII.151), bromide (VIII. 156)-HBr was condensed in situ with 4-aminobenzoic acid and the product, 4-amino-4-deoxypteroic acid (APA), was treated directly with a mixture of formic and acetic acid to obtain the W °-formyl derivative (FmAPA, 65% yield) [292]. Condensation of FmAPA with y-r-butyl a-methyl L-glutamate to form the diester (VIII. 155) was accomplished in 82% yield by a modified mixed anhydride procedure involving four cycles of in situ carboxyl group reactivation. Hydrolysis of the methyl ester and W -formyl group at the same time with NaOH proved impossible as a result of an unforeseen loss of the y-t-butyl ester. When the a-methyl ester was first removed under mild conditions with Ba(0H)2, however, the relatively stable V -formyl derivative (VIII.154) was isolated satisfactorily in 79% yield. Subsequent cleavage of the W -formyl group was then accomplished by carefully controlled hydrolysis in 0.25 M NaOH (1.75 h at 25 °C). In an alternative synthesis, FmAPA was activated by reaction with bis(4-nitrophenyl) carbonate to obtain the corresponding... 

Fig. 9.72Structures of MCPA(4-chloro-2-methylphenoxyacetic acid (I)), its metabolites 4-chloro-o-cresol (II), 5-chloro-3-methyl catechol (III), 4-chloro-2-methyl muconic acid (IV), reagent pentafluorobenzyl bromide (V), and the derivatives VI-VIII from l-lll Source Reproduced with permission from the American Chemical Society [155]... 

The structure and absolute stereochemistry of yohimbine (V) have been known for some time (Volume VII, p. 50). The absolute configuration at C-17 has been determined by the method of Prelog, as follows the phenylglyoxalate of yohimbine (VI), on treatment with methyl magnesium bromide, generated an ester (VII) which on hydrolysis gave a substantial yield of L-( + )-atrolactic acid (VIII) (3). 

A recent paper by a Rusian team [18] describe tte use of a few new surfiners, one being cationic, namely JV-decylaceto-2-methyl-5 vinylpyridinium bromide (V), and the others being anioic, namely decyl (or dodecyl), sodium ethyl sulfonate, methacrylamides (VI), decyl (or dodecyl)-phenyl (Na or K sulfonate) acrylate (VII), and decyl ester of sodium (or K or NH4) sulphocin-namic acid (VIII). These surfmers were used for emulsion polymerization of styrene, butylacrylate or chloroprene, in the presence of KPS or AIBN without any other surfactants. It should be noted that the consumption of these surfactants take place early in the polymerization process which is faster than in... 

Reagents and conditions i) 2-nitrobenzyl bromide, DMF, 70°C ii) a) Na2S20<, EtOH, reflux, b) HBr, MeOH, dioxane Hi) PMB chloride, py, CHsCIs iv) methyl 4-formylbenzoate, NaOMe, MeOH, reflux v) aminomethyl resin, AcOH, MeOH/dioxane vi) NaOMe, MeOH, reflux vii) toluene, DMF, distillation viii) KOtBu, reflux. 

Vinyl Magnesium Route. A direct route to dieno-p osides or VI) is shown in Figure 3b, introduction of the vinyl residue is effect by reacdon of vinyl magnesium bromide and a pyranoside-ulose VII (, follow by eliminadon of the tertiary hydroxyl group in VIII. This route could, in pnnciple, be common for both methyl, and desmethyl dienic systems.. ... 

The reaction of benzyl chloride with metallic nickel in the presence of methyl acrylate was carried out at 85°C, and the expected addition product methyl 4-phenylbutanoate was formed in 17% yield (Equation 7.12). The reaction with acrylonitrile gave 4-phenylbutanenitrile in 14% yield together with cis- and tra 5-4-phenyl-2-butenenitriles, 4-cyano-6-phenylhexanenitrile, and 2-ben-zyl-4-phenylbutanenitrile (Equation 7.13). The results suggest the presence of a benzylnickel(II) chloride complex (1), which could have been formed by the oxidative addition of benzyl chloride to the metallic nickel (Scheme 7.7). The complex (I) would then be expected to add to the electron-deficient olefins, affording the addition product (111) via intermediate complex (IV). The formation of cis- and tra s-4-phenyl-2-butenenitrile (V) is reasonably explained by the reductive elimination of nickel hydride from intermediate (IV), which is analogous to the substitution reaction of olefins with alkylpalladium compound [158] and to the addition-elimination reaction of bis(triphenylphosphine) phenylnickel(II) bromide with methyl acrylate to yield methyl cinnamate [130]. Furthermore, intermediate (IV) seems to add another molecule of acrylonitrile to give the 1 2 adduct 4-cyano-6-phenylhexanenitrile (VI). 2-Benzyl-4-phenylbutanenitrile (VIII) would be formed by the metathesis of complex IV and the benzylnickel chloride (I). 

These effects, determined with tertiary chlorides, unquestionably refer to 8n1 reactions so also do Lewis and Boozer s effects on acetolysis and formolysis—-if we can rely on the constancy of the effect of a-deuteration (Table VIII). The /3-effects then suggest that formolysis of the secondary bromide and solvolysis in aqueous ethanol of the tosylate are also SnI—or nearly so, unless bimolecular displacement reactions are also subject to similar isotope effects. Shiner (117) had however already shown that this was not so, since deuteration in the two methyl groups of isopropyl bromide did not lead to an experimentally significant effect on the displacement reaction with ethoxide ion in ethanol. It is thus also reasonable to interpret the very small effect (AAF" = 6 cal.) cited by Lewis (74f) for acetolysis of ethyl-2d8 brosylate as evidence that acetolysis of primary sulfonate esters is borderline if not Sn2. This conclusion, already suggested by the abnormally low a-effect for unassisted acetolysis of phenylethyl tosylate [Table VIII and text of Sec. VA, 2(b) 1 is supported by a similarly... 

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