4- Amino-1 -substituted imidazoles acetylation

One of the key methods of synthesis of imidazo[l,2-a]quinoxalines on the basis of imidazoles is Ali-type synthesis. In this case, imidazole ring annulation is a result of formation of the C(3a)-C(4) bond. In particular, l-(2-acylaminophenyl)- or 1-(2-amino-carbonylaminophenyl)imidazoles 143, obtained by the reaction of N-(2-aminophenyl)imidazole 86c and acetyl chlorides or isocyanates, are converted under the action of phosphorus(V) oxochloride into 4-substituted imidazoquinox-alines 144 (Warner and Luber 1979a, b, c, 1980a, b, c, d, e Lamberth 1999 Chen et al. 2002b). More than 100 imidazo[l,2-ti]quinoxalines have been synthesized by this method (Scheme 4.65). 

The most prominent cellulose ester produced on the industrial scale is cellulose acetate. The reaction is usually performed with acetic anhydride and with sulfuric acid as a catalyst. To minimize heterogeneities, acetylation is allowed to run nearly to completion, and subsequently partial ester hydrolysis is initiated by the addition of water until a desirable solubility is achieved that corresponds to a DS of about 2.5. Such higher acyl homologues as propanoyl or butanoyl exhibit more thermoplastic properties. Many specialized esters such as chiral (-)-menthyloxyacetates, furan-2-carboxylates, or crown-ether-containing acylates have been prepared on the laboratory scale and characterized by NMR spectroscopy. Various procedures have been applied, using anhydrides and acyl chlorides as acylating agents in combination with such bases as pyridine, 4-dimethylaminopyridine (DMAP), or iV,iV -carbonyldi-imidazole. The substitution pattern of cellulose acetates has also been modified by postchemical enzymatic deacetylation. Cellulose 6-tosylates have been used as activated intermediates for nucleophihc substitution to afford 6-amino-6-deoxy, 6-deoxy, or 6-deoxy-6-halo-celluloses. ... 

The substitution of sodium acetate or N-methyl-imldazole for pyridine in the preparation of alditol acetate derivatives for the capillary g.c. analysis of neutral and amino-sugars using selected ion monitoring m.s. detection has been examined. While N-methyl-imidazole effected full acetylation of alditols in the presence of borates and water, it led to a higher detector background than the more tedious use of sodium acetate. Muramic acid produced two alditol acetate derivatives, the lactams (1) and (2), in a reproduceable fashion only in the sodium acetate-catalyzed procedure... 

A variety of alditol-l-yl substituted heteiocyclic derivatives have been synthesized. The tetiazole derivative (94) was derived riom maltose, and convened into the corresponding 1,3,4-oxadiazoles (95) on acetylation or benzoylation. Reaction of l-arylamino- or 1-alkylamino-l-deoxy-D-arabino-hexuloses with cyanamide gave the imidazole derivatives (96). Fructosazine (97) and deoxyfiructosazine (98) were simultaneously formed by self-condensation of 2-amino-2-deoxy-D-glucose in neutral to basic aqueous solutions, and were shown to have DNA strand breaking activity. Condensation of 2-amino-2-deoxy-D-glucose with aryl isocyanates gave adducts such as (99) that exist in solution as (R,5)-mixtures in which the (R)-fonn predominates. ... 

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