Hydrolysis, hydroxylamine synthesis

Hydroxylamine can be prepared by a variety of reactions involving the reduction of nitrites, nitric acid or NO, or by the acid hydrolysis of nitroalkanes. In the conventional Raschig synthesis, an aqueous solution of NH4NO2 is reduced with HS04 /S02 at 0° to give the hydroxylamido-A ,A -disulfate anion which is then hydrolysed stepwise to hydroxylammonium sulfate ... 

The preferred industrial method of carvone synthesis utilizes the selective addition of nitrosyl chloride to the endocyclic double bond of limonene. If a lower aliphatic alcohol is used as solvent, limonene nitrosochloride is obtained in high yield. It is converted into carvone oxime by elimination of hydrogen chloride in the presence of a weak base. Acid hydrolysis in the presence of a hydroxylamine acceptor, such as acetone, yields carvone [88]. 

A method for the synthesis of optically active hydroxylamines from optically active primary amines with retention of configuration is based on the conversion of the amines to corresponding benzylimines followed by oxidation to 3-phenyloxaziiidines (74). Subsequent hydrolysis leads to hydroxylamines (Scheme 16). This sequence has been extended to the synthesis of optically active N-hydroxy-a-amino acid esters. ... 

In the synthesis of hydroxamic acid 19a, having a free quaternary amino group (see Scheme 4.4), the intermediate sulfone 21 was synthesized by Pd-catalyzed reaction of phenol with p-bromo derivative 20 [24], Lithiation of 20, followed by nucleophilic addition to the A-Cbz imine of trifluoropyruvate 22 [25] afforded the a-CF3 a-amino acid derivative 23 in fair yields. Basic hydrolysis of the ester function gave the carboxylic acid 24, which was submitted to condensation with ()-15 n-hydroxylamine, affording hydroxamate 25. The subsequent hydrogenolysis of 25 afforded the target molecule 19a. 

Sandmeyer isonitrosoacetanilide isatin synthesis. Formation of isonitrosoacetodi-phenylamidine by condensation of chloral hydrate, hydroxylamine, and aniline cyclization with concentrated sulfuric acid and quantitative hydrolysis to isatin on dilution. 

Unger and coworkers [26] described the synthesis of FPS containing l,2-epoxy-3- pro-poxypropyl groups. Initially, polyethoxysiloxane (MW = 800) was prepared from TEOS by acid hydrolysis, which was further used in hydrolytic polycondensation with 1,2-epoxy-3-propoxypropyltriethoxysilane. Homogeneity of the reaction medium in the second stage was maintained by addition of sodium or ammonium hydroxide, so that the final product contained either 1,2-dihydroxyl-3-propoxypropyl or hydroxylamine functional groups. 

Petrini and co-workers used the bis(methoxymethyl)-protected nitrone 150, also derived frern L-tartrate, as an electrophile rather tfaiui as a 1,3-dipole (Scheme 21, top line) (89). In their key step, reaction with 4-ben loxybutylmagnesium bromide gave the cyclic hydroxylamine 151 in 82% yield (de 90%). Transfer hydrogenation with ammonium formate and a palladium catalyst cleaved both the hydroxylamine and the benzyl ether, affording the aminoalcohol 152. Cyclization via the corresponding primary chloride created the protected indolizidine 153, acidic hydrolysis of t ch completed this short synthesis of ( + )-132 in 16%... 

Coenzyme A (CoA) derivatives of bile acids were prepared [33,34] by a modification of the mixed anhydride procedure for the synthesis of palmityl CoA. A yield of 70% was calculated from the quantity of cholylhydroxamate formed after treatment of the CoA derivative with hydroxylamine. By modification of this procedure and purification of the products by chromatography on Sephadex LH-20, aqueous solutions of CoA derivatives of cholic, chenodeoxycholic, deoxycholic, and lithocholic acids were pbtained, frozen at - 70°C, and shown to be free from hydrolysis for several months [35]. 

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