DMF acetal

Solvent Heptane Pyridine DMF Acetic acid Methanol Water... 

Acy 1-4-amino-1,5-dihydro-2-pyrrolones (6) (type Z in Scheme 1) possess the features of cyclic enaminediones. The push-pull-7r system decreases the nucleophilicity of the amino group. Therefore N-acylation with carboxylic acid chlorides requires relatively drastic conditions (dioxane, 100°C, K2C03). In particular, the reaction of the highly reactive DMF-acetal 8 to formamidine 9 succeeds only while refluxing in benzene (87TH1). (See Fig. 3.)... 

An analogous scheme is used for the synthesis of the cardiotonic agent milrinone [28]. The key aminoformyl derivative (26-2) is obtained in this case by condensation of 4-pyridylacetone (26-1) with DMF acetal. Reaction with cyanoacetamide in the presence of a strong base proceeds exactly as above to give the pyridone (26-3) by a parallel set of transformations. Note that the nitrile is left as such in this drug. 

The quinoline-based tyrosine kinase inhibitor pelitinib (31-11) incorporates a Michael acceptor function in the side chain that can form a covalent bond with a nucleophile on the target enzyme. Such an interaction would result in the irreversible inhibition of the target kinase. Reaction of aniline (31-1) with DMF acetal leads to the addition of a carbon atom to aniline nitrogen in the form of an amidine (31-2). This intermediate is next reacted with nitric in acetic acid to form the nitrated... 

Potential dyes in which the pyran rings are separated by three carbon atoms are formed by reaction of a 4-methylpyrylium salt (113) with DMF-acetic anhydride and heating the resultant 4-formylmethylenepyran (114) with another molecule of 4-methylpyrylium salt. The product (115) absorbs strongly at 598 nm (e 267 000 mol-1 cm-1). The relationship between colour and structure in such compounds has been discussed in detail (73T795). 

A pulse polarographic method to determine dantrolene sodium and its major metabolites in urine after ethyl acetate extraction has been reported [181]. The ethyl acetate is brought to a residue and the dantrolene plus the total extract-able metabolites are analyzed for reduction of the azomethine linkage at -0.86 V in a DMF-acetate buffer (pH 4.0). The nitro compounds are simultaneously determined in the same media as dantrolene equivalents from the reduction of the nitro group at -0.26 V (see Fig. 26.13). The difference between the two determinations represents the metabolites not containing the nitro group. Levels as low as 0.1 fig/mL can be determined for either functional group. 

Fig. 9.16. Gentle esterification of a carboxylic acid II with DMF acetal (A upper part). The lower part gives an example of a chemoselective—since neither a cleavage of the substrate s Boc group nor a reaction on its stereocenter takes place—esterification according to the procedure discussed.

The esterification of carboxylic acids with DMF acetal (Formula A in Figure 9.16) proceeds in line with the esterification of carboxylic acids with ortho formates (Formula A in Figure 9.15). The reaction conditions are even milder since no acid needs to be added. This is due to the fact that all cationic intermediates of an esterification according to Figure 9.16 are iminium ions in which the positive charge is better stabilized than by the cationic intermediates of esterifications shown in Figure 9.15, because they are carboxonium ions. 

Reaction of the 2-amino-1,3-dithiolylium bromide (156) with sodium hydrogen sulfide in DMF/acetic acid at room temperature leads to a 91% yield of l,3-dithiole-2-thione (21) (75S277). 

In an intramolecular reaction with jV,jV-diethylformamide or AyV-dimethylacetamide diethyl acetal, enaminones are known to react at the nitrogen to form amidines42. The corresponding products from acetamide acetals can be converted to 2-aminoquinolines by condensation with DMF acetals or to 1,4-dihydroquinolines by cycloaddition with diethyl maleate (see Section II.A.5) (equation 26). 

Enol acetates of oxonucleosides. These derivatives of oxonucleosides are available by reaction of a nucleoside first with a DMF acetal and then with acetic anhydride. This method is limited to compounds with the 0x0 group in the 4 -position and with a free CO—NH group in the pyrimidine ring. Previous methods of enol... 

SCHEME 6.42 3,4-Unsaturated sugars are available via DMF acetals followed by elimination. 

The relative abilities of the leaving groups in the cathodic cleavage of //-methoxy-carbonylbenzyl carboxylates have been measured in a DMF acetate buffer. There seemed to be no recognizable correlation between the relative rate of cleavage and either the of the conjugate acid of the leaving anion or the peak potential in cyclic voltammetry [61]. 

The Still-Wittig rearrangement of stannylated cis-ethers (11) gives trans homoallylic alcohols (12) selectively (equation 5). If the underlying alcohols (R = Me) are rearranged under Biichi s conditions (DMF acetal, xylene, reflux), trans selectivity is achieved, too, but yields are lower (41-49%). ... 

Reaction of the derivative 149 (R1 = R2 = 2,5-dimethyl-3-thienyl) with DMF acetal gives the amidine 150 (85%) (Scheme 28) (01MI2424). Condensation of the derivatives 149 (R1, R2 = alkyl or aryl) with 2,5-dimethoxytetrahydrofuran, in the presence of 4-chloropyridinium chloride, gives the pyrrole derivatives 151 (25-86%) (Scheme 28) (96JHC2007, 98JHC1313). 

Fang, F.G., Feigelson, G.B., and Danishefsky, S.J., A total synthesis of magaUanesine. DMF acetal mediated cyclodehydration of a methyl ketone thioimide. Tetrahedron Lett., 30, 2743, 1989. 

A. similar set of transformations was also done in an antipodal series w c led to (-l-)-204. Thus D-gluconic acid y-lactone (215) was converted via a straightforward protection and reduction sequence to furanoside 216. Reductive deoxygenation via the intermediate DMF acetal gave l-210 in 11% overall yield from 215. Conversion of e r-210 to a mixture of (-l-)-methyl nonactate [(+ )-204] and ( + )-8-epi methyl nonactate [(-I-)-180] was then accomplished in a manner identical to that described for the (-)-enantiomer. 

Direct chlorination of 2-phenyl-6-hydroxy-3(2//)-pyridazinone (50) in polar solvents (DMF, acetic acid) resulted in chlorination of the phenyl ring and rearrangement of the pyridazinone to give the trichlorophenylaminopyrrole-2,5-dione (51) as the major product the dichlorophenyl-aminopyrrole-2,5-dione (52, Scheme 7) was isolated as an intermediate. It is proposed that the pyridazinone is less stable after dichlorination of the phenyl ring and rearranges to the A -amino-maleimide (52), but the reasons for this are unclear <89JHC1649>. 

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