O-Acylamino acid

Quinazoline 3-oxides were first prepared by Awers and von Meyen-burg in 1891 by the dehydration of o-acylamino benzophenone oximes with acetic acid-acetic anhydride and were assigned the in-dazole structure (33). This was then modified by Bischler to the... 

The Ugi reaction is the four-component condensation of an amine, aldehyde or ketone, carboxylic acid and isocyanide to give an o -acylamino amide [22-24], Although this process has the potential to introduce considerable diversity, the products themselves are not heterocycles but through appropriate choice of substrates, latent functionality in one of the precursors can intercept either an intermediate or further derivatize the acylamino amide Ugi product through post-modification. Thus variants of the Ugi reaction have been investigated under microwave-assisted conditions for the synthesis of diverse heterocyclic libraries [16,19-24],... 

Erlenmeyer synthesis org chem Preparation of cyclic ethers by the condensation of an aldehyde with an a-acylamino acid in the presence of acetic anhydride and sodium acetate. 3r-l3n,mT-3r sin-th3-s3s erucic acid org chem C22H42O2 A monoethenoid acid that is the cis isomer of bras-sidic acid and makes up 40 to 50% of the total fatty acid in rapeseed, wallflower seed, and mustard seed crystallizes as needles from alcohol solution, insoluble in water, soluble in ethanol and methanol. o rus ik as ad erythrite See erythritol. er o.thrTt ... 

In the third transition state (TS3), the neutral catalyst is recovered by transferring the proton back from the catalyst to the substrate. In other words, the (former) azlactone ether oxygen atom deprotonates the tertiary ammonium ion. For proton transfer, again a low-barrier hydrogen bond is formed (N—O distance 2.479A, <(0,H,N) = 166.2°). In the product complex, the catalyst is neutral and the N-acylamino acid ester is bound in its iminol form to the catalyst (Product [iminol]). Finally, an additional 66.6kJ/mol are gained by the subsequent iminol-amide tautomerization (Product [amide]). 

Acylhydrazides of anthranilic acid (35, R = NHCOR ) give 3-acylamino-l,2,3-benzotriazin-4(3H)-ones (10, R = NHCOR on treatment with nitrous acid. The triazine hydroxamic acid (40) and its benzo-substituted derivatives are available by diazotization of the corresponding o-aminobenzohydroxamic acids. The pyrido[2,3-e]triazine analog (41) was prepared similarly from 3-aminoisonicotino-hydroxamic acid, but the isomeric 2-aminonicotinohydroxamic acid failed to react under the same conditions to give 42. ... 

Current Work and Industrial Applications. Recent efforts have been directed primarily toward refining the original process by using standard o -(acylamino)acrylic acids as substrates. The synthetic efficiency (in-... 

Some reactions of munchnones occur via acylamino ketenes, the covalent valence tautomers of the betaines. The ketenes are intermediates in the thermolysis (see Scheme 22) and in the formation of azetidinones from imines (equation 69) they are thought to be involved in the aminolysis of the mesoionic compounds, which results in amides of a-acylamino acids, and in the formation of the benzodioxin (247) by the combined action of acetic anhydride and tetrachloro-o-benzoquinone on Af-benzoylalanine (equation 70). 

Thermal dehydration of o- (acylamino)phenols is the method of choice for the preparation of benzoxazoles (equation 96) and other annulated oxazoles. 0,iV-Diacyl derivatives of o-aminophenols cyclize at lower temperatures than do the monoacyl compounds. The synthesis is often carried out by heating the aminophenol with the carboxylic acid or a derivative, such as the acid chloride, anhydride, an ester, amide or nitrile. The Beckmann rearrangement of oximes of o-hydroxybenzophenones leads directly to benzoxazoles (equation 97). 

In a Study of the formation of benzimidazoles by the peroxy acid-catalyzed cyclization of o-acylamino-iV,lV-dialkylaniIines, it has been demonstrated that the reaction proceeds via an iV-oxide intermediate, since it has proved possible to synthesize this N-oxide and cyclize it under the reaction conditions (B-73MI40800). Both ortho-N-acylated and -N-... 

Mixed Anhydride Coupling. This very popiilar method, involving the use of alkyl chloroformates as reagents to make anhydrides v/ith acylamino acids or acylpeptides, has been reinvestigated. Determann, Heuer, Pfaender and Reinartz o have shown that exposinre of the mixed anhydride... 

Annulation of an o-(acylamino)aniline has been induced by acidic or nearly neutral conditions (see p. 24), but an aqueous alkaline medium is also successful for this reaction. In another method, ethyl 2-eUioxyquinoline-l-carboxylate is used [2766]. 

Pentamethyleneoxaziridine (459) has been used to 5-aminate thiouracils <91S327>. Similarly, either 3,3-pentamethylenoxaziridine or hydroxylamine-O-sulfonic acid reacts with 1-acylamino, with 1-phenylureido-, or with l-arylaminopyrimidine-2-thiones (458) to form 5-aminated derivatives (461). A postulated intermediate (460) is arrived at by nucleophilic attack by the sulfur at the nitrogen of the oxaziridine ring. The structure of the A-ylide (461 Ar = p-tolyl, R = Ph) in the solid was verified by x-ray analysis <93T3767>. 

Some of the phosphine ligands used for the Rh-catalyzed asymmetric hydrogenation of o -(acylamino)acrylic acids are shown in Scheme 4... 

Oxazoles and 4,5-dihydrooxazoles can be transformed into quinolines. For instance, 5-(o-acylamino-aryl)oxazole-4-carboxylic esters 104, made from benzoxazinones 103 and isocyanoacetic ester, are converted into 3-aminO 4-hydroxy-2-quinolones 105 in an acid medium [109]. 

Quinazolines can be prepared by several methods. AT-Acylanthranilic acids undergo cyclization with ammonia or primary amines via amides 14 forming quinazolin-4(3ii0-ones 15 (Niementowski synthesis). Alternatively o-(acylamino)benzaldehydes or -acetophenones react with ammonia producing quinazolines 16 (Bischler synthesis) ... 

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