Carboxylic acids with sodium chlorite

OXIDATION OF PRIMARY ALCOHOLS TO CARBOXYLIC ACIDS WITH SODIUM CHLORITE CATALYZED BY TEMPO AND BLEACH 4-METHOXYPHENYLACETIC ACID... 

Dalcanale, E., Montanari, F. Selective oxidation of aldehydes to carboxylic acids with sodium chlorite-hydrogen peroxide. J. Org. Chem. 1986,51,567-569. 

Zhao, M. Li,J. Mano, E. Song, Z. T chaen, D. M. Grabowski, E.J.J. Reider, P.J., Oxidation of Primary Alcohols to Carboxylic Acids with Sodium Chlorite Catalyzed by TEMPO and Bleach. ... 

Dalcanale, E. Selective Oxidation of Aldehydes to Carboxylic Acids with Sodium Chlorite-... 

One feature of this oxidation system is that it can selectively oxidize primary alcohols in preference to secondary alcohols, as illustrated by Entry 2 in Scheme 12.5. The reagent can also be used to oxidize primary alcohols to carboxylic acids by a subsequent oxidation with sodium chlorite.34 Entry 3 shows the selective oxidation of a primary alcohol in a carbohydrate to a carboxylic acid without affecting the secondary alcohol group. Entry 5 is a large-scale preparation that uses NaC102 in conjunction with bleach as the stoichiometric oxidant. 

Effective conditions for oxidation of aldehydes to carboxylic acids with KMn04 involve use of t-butanol and an aqueous NaH2PC>4 buffer as the reaction medium.173 Buffered sodium chlorite is also a convenient oxidant.174 175 An older reagent for carrying out the aldehyde — carboxylic acid oxidation is silver oxide. 

Benzo[ ]perimidinone carbaldehyde and carboxylic acid derivatives have also been prepared by alkyl oxidation. Thus, treatment of the 2-methyl derivative 588 with selenium dioxide at reflux in dioxane gave the aldehyde 589, which then gave carboxylic acid 590 on reaction with sodium chlorite <2001JME2004>. 

Immobilized TEMPO has been used for the one-pot oxidation of alcohols to carboxylic acids as well.26 For this purpose TEMPO resin 1 was combined with two ion-exchange resins loaded with chlorite anions and hydrogen phosphate in the presence of catalytic amounts of potassium bromide and sodium hypochlorite in solution. The reaction required work-up for the removal of salts, but tolerated several protecting schemes and afforded pure products in good to excellent yields. The reaction is initiated by catalytic TEMPO oxidation of alcohols to aldehydes driven by dissolved hypochlorite followed by oxidation to the carboxylic acids effected by chlorite. 

In the final stages of the total synthesis of ustiloxin D, M.M. Joullie and co-workers had to install the amide side-chain onto the already assembled macrocycle.To achieve this goal, the macrocyclic primary alcohol was treated with the Dess-Martin periodinane to generate the corresponding aldehyde, which was subsequently treated with sodium chlorite to afford the carboxylic acid. The carboxylic acid was then coupled with the benzyl ester of glycine to complete the installation of the side-chain in 66% yield for three steps. 

Aromatic aldehydes are oxidized a) with sodium chlorite (NaC102) in the presence of sulfamic acid to the corresponding carboxylic acid (Lindgren-Nilson reaction) and b) with hydrogen peroxide or w-chloroperbenzoic acid to the corresponding phenols (see Scheme 16). 

This methodology provides a general synthesis of L-amino acids in 92-96% ee and in chemical yields of about 40-60%. Thus reaction of 3 (X = Br) with NaN3 under phase-transfer conditions provides 6, which is homologated to the 1-chloro-2-azidoboronate 7. This product is oxidized by sodium chlorite directly to an azido carboxylic acid (8). Hydrogenation of 8 provides L-amino acids (9). 

For the synthesis of amino acids, the reaction of an a-haloalkyl boronic ester 4 with sodium azide and a phase-transfer catalyst in dichloromethane/water requires a large excess of azide in order to form the a-azidoalkyl boronic ester 5 with only 1-2% epimer34. With the exception of R1 = benzyl, where epimerization of 4 is relatively rapid, bromoalkyl boronic esters are preferred. Chloroalkyl boronic esters react so slowly that the azide and dichloromethane may generate hazardously explosive diazidomethane65,66. Chain extension of 5 to 6 proceeds normally. Sodium chlorite, which is known to oxidize aldehydes to carboxylic acids67-69, also oxidizes a-chloroalkyl boronic esters to carboxylic acids34. The azido acid is hydrogenated to the amino acid. 

Oxidation of the aldehyde groups of SVI-IO4 with weakly acidic sodium chlorite " for various times gave products (see 17, SVI-IO4-BH4-CIO2) in which from 16 to 81% of the aldehyde groups had been oxidized, and which showed decreasing precipitation in anti-Pn VI horse and rabbit sera with increasing content of carboxylic acid groups. The product from the con-... 

A good method for the direct conversion of alcohols to carboxylic acid uses 2,2,6,6-tetramethylpiperidin-l-oxyl (TEMPO) 51, in conjunction with the co-oxidant sodium chlorite (NaC102) and sodium hypochlorite (NaOCl) as a catalyst. See M. Zhao, J. Li, E. Mano, Z. Song, D. M. Tschaen, E. J. J. Grabowski and P. J. Reider, J. Org. Chem., 64 (1999), 2564. 

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