Carboxylic acid anhydrides preparation

Attempts to synthesize C-terminal peptide aldehydes using other reductive techniques are less successful. 24"29 The reduction of a-amino acid esters with sodium amalgam and lithium aluminum hydride reduction of tosylated a-aminoacyldimethylpyrazoles resulted in poor yields. 26,29 The Rosemond reduction of TV-phthaloyl amino acid chlorides is inconvenient because the aldehyde is sensitive to hydrazine hydrate that is used to remove the phthaloyl group. 27 28 jV -Z-Protected a-aminoacylimidazoles, which are reduced to the corresponding aldehydes using lithium aluminum hydride, are extremely moisture sensitive and readily decomposed. 25 The catalytic reduction of mixed carbonic/carboxylic acid anhydrides, prepared from acylated a-amino acids, leads to poor reproducibility and low yields. 24 The major problems associated with these techniques are overreduction, racemization, and poor yields. 

On the other hand, 1 g of 7-amino-3-methyl-3-cephem-4-carboxylic acid was suspended in 20 ml of methanol, and 1.4 g of triethylamine was added thereto to be dissolved, and 0,4 ml of acetic acid was further added thereto. This solution was cooled to -20°C and the mixed acid anhydride prepared previously was added thereto. After the mixture was reacted at -20°C for 1 hour, the temperature of the reaction mixture was raised to 0°C over a period of 1 hour, and the mixture was reacted for 3 hours at the same temperature. 

Polysilane(II) was prepared by the method described in the previous literature(25). Polysilane(III)s were prepared by reacting polysilane(II) with carboxylic acid anhydrides in THF catalyzed by triethylamine at 20-50OC(Table 2)(26). Polysiloxane(I) was synthesized as follows. To 3.3g of NaOH in 40mL of water, lOg of M-... 

JR Vaughan, RL Osato. The preparation of peptides using mixed carbonic-carboxylic acid anhydrides. J Am Chem Soc 74, 676, 1952. 

Carboxylic acids are prepared hy the hydrolysis of acid chlorides and acid anhydrides, and acid- or hase-catalysed hydrolysis (see Section 5.6.1) of esters, primary amides and nitriles (see Section 5.6.1). 

Furopyrylium salts (43, 55) have been repeatedly mentioned in the foregoing subsections. They may be prepared from acetonylfurans (42,54) and carboxylic acid anhydrides in the presence of perchloric acid. Benzofuro[3,2-6]pyrylium salts have been synthesized from /3-coumaranone and /3-diketones, e.g. equation (15) (B-78MI31704). 

Sulfonamides prepared from 9-(chlorosulfonyl)anthracene and polystyrene-bound primary amines can be converted into amides by N-acylation of the sulfonamide (carboxylic acid anhydride, DMAP, pyridine, THF, 24 h) followed by nucleophilic desulfo-nylation with neat 1,3-propanedithiol/DIPEA [213] (Entry 4, Table 10.13). An example of the use of sulfonamides as linkers for amines is given in Table 3.23. 

It is possible to prepare esters of phenols with carboxylic acid anhydrides or acid halides, and phenyl ethers by reaction of benzenolate anion with halides, sulfate esters, sulfonates, or other alkyl derivatives that react well by the SN2 mechanism ... 

The polymerisation of a-aminoacid A-carboxyanhydride, which is accompanied with the elimination of carbon dioxide, constitutes a convenient method for preparing high molecular weight polypeptide. This polymerisation, with the use of a-aminopropionic acid (alanine) A-carboxylic acid anhydride as a monomer, was also carried out in the presence of coordination catalysts such as group 2 and 3 metal alkyls [168-174] or their combinations with water, secondary amine or alcohol [168,173] and yielded polyalanine (Table 9.2). 

Process chemists studied an approach to 8 using the readily available indan-1-one-3-carboxylic acid 20 prepared from phenyl succinic anhydride via Friedel-Crafts closure (Scheme 6). After esterification (yielding 21), homologation of the carbonyl via aminomethylation proceeded in high efficiency to give 25. In the presence of... 

Alternatively, titanoxanes can be prepared by reaction of tetraalkyl titanates with carboxylic acid anhydrides (30) ... 

Syntheses of 2-substituted indoles from (2-aminobenzyl)triphenylphosphonium salts have been achieved either by cyclization with carboxylic acid anhydrides in the presence of triethylamine, or acyl chlorides in 2,6-lutidine <02TL2885>. In a related study, the acylated indoles 65 have been prepared from the phosphonium salts 66 in a process involving extrusion of a one-carbon fragment. A mechanistic rationale for these findings was also provided by the authors <02TL8893>. 

A large number of stable /e-organo tellurocarboxylates were prepared from tellurolates and aliphatic1,2 or aromatic2 carboxylic acid chlorides or aliphatic carboxylic acid anhydrides . The tellurolates were obtained by reduction of diorgano ditelluriums with sodium borohydride. 

Diorgano tellurium dicarboxylates were prepared from dialkyl and diaryl tellurium derivatives. Aliphatic carboxylic acids, aromatic carboxylic acids, their sodium or silver salts, and carboxylic acid anhydrides were used as reagents. Dicarboxylic acids such as succinic acid and phthalic acid were reported to give monomeric carboxylates when... 

A convenient single-step method for the preparation of diaryl tellurium dicarboxylates in 82 to 92% yields involves the reactions of the diaryl tellurium with hydrogen peroxide and carboxylic acids2,3. The reaction probably proceeds via diaryl tellurium oxides as intermediates. Carboxylic acid anhydrides can be used instead of the carboxylic acids. 

The starting materials for the preparation of 1,3-benzotellurazoles are aromatic tellurium compounds that contain an amino functionality in an orv/to-position to the tellurium atom. The reduction of 2-benzeneazophenyl tellurium trichloride with sodium borohydride in ethanol generates 2-aminobenzenetellurol. This compound is acylated with carboxylic acid anhydrides and the acylaminobenzenetellurol cyclized by treatment with concentrated... 

A cyclization reaction involving the sulfonamide 267 finalized an efficient synthetic approach to the COX-inhihitor 268 after subsequent simultaneous ester hydrolysis and detosylation (Equation 82) <2003JOC4104>. Indoles have also been prepared by reaction of (2-aminobenzyl)triphenylphosphonium salts with carboxylic acid anhydrides in the presence of a base <2002TL2885>. Exposure of o-(benzoylamino)benzonitriles to a-bromoketones under basic conditions gives 3-aminoindole derivatives <2001BML2169>. 

Table 8 Examples of 3-Alkyl- and 3-Aryl-[l,2,4]triazolo[4,3-a]pyridines Prepared from 2-Hydrazinopyridines and Carboxylic Acids, Anhydrides, Esters or Ortho Esters <66JOC25i, 78JHC439.7OJHC703,70JHC1019)...

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