Benzohydroxamic acid chloride

Benzohydroxamic acid chloride (the oxime of benzoyl chloride) adds on to the benzodiazepin-2-one (106.8) at ambient temperature with loss of chlorine. 

The 3-o-ch orophenvl-5-methvlisoxa2ole4-carboxylic acid, from which the acid chloride was prepared, was obtained by hydrolysis of the ester product of the reaction between o-chloro-benzohydroxamic chlorideand ethyl acetoacetate in methanolic sodium methoxide. Reaction with thionyl chloride gave the starting material. 

A solution of thionyl chloride (1.42 g, 12 mmol) in dry benzene (CAUTION) or ether (10 ml) is added dropwise to a stirred solution of AT-phenyl-benzohydroxamic acid (2.13g, lOmmol, Expt 6.87) in dry benzene (CAUTION) or ether (100ml) at 0-5 °C during 20 minutes. The reaction mixture is stirred at the same temperature for 30 minutes and at room temperature for 1 hour. Water (50 ml) is added. The solvent layer is washed with a 5 per cent solution of sodium hydroxide (10 ml) and then with water until free of alkali. After drying over anhydrous sodium sulphate and concentrating, o-chlorobenzanilide (1.90 g, 84%) is isolated, and is recrystallised from aqueous 30 per cent ethanol. The m.p. is 104 °C (1). 

A silver ion-mediated desulfurization of thiocarbonyl compounds 163 or 164 followed by condensation with benzohydroxamic acid in the presence of excess triethylamine affords, respectively, dioxazole derivatives 165 or 166 (Scheme 25) <2002H(57)143>. Other reports concern the synthesis of l,4-(oxa/thia)-2-azoles 170-173 from unusual four-atom components such as the sulfur diimides 167, the thietan sulfimide 168, and the carbimidoyl chloride 169 <1996CHEC-II(4)530>. 

Derivatives. For the preparation of benzohydroxamic acid, isolated as the potassium salt, separate solutions of 46.7 g. (0.67 mole) of hydroxylamlne hydrochloride in 240 ml. of methanol and of 1 mole of potassium hydroxide in 140 ml. of methanol are prepared at the boiling points, cooled to 30-40°, and the second solution is added to the first. After cooling in ice to ensure complete separation of potassium chloride, 0.33 mole of ethyl benzoate is added with shaking. The mixture is filtered quickly... 

Rearrangements. Hurd and Bauer" added tosyl chloride in chloroform to a suspension of the sodium salt of benzohydroxamic acid (1) in the same solvent, noted a vigorous reaction, and characterized the product as benzo-(phenylcarbonyl-hydroxamic) acid (6). They postulate that the initial product is the tosylate (3), that this is a much stronger acid than (1) and so abstracts sodium from the salt (2) to give the salt (4), which undergoes concerted cleavage and Lessen rearrangement to phenylisocyanate (5) and sodium tosylate. The phenylisocyanate is then captured by (1) to yield the final product (6). 

Benzohydroxamic acid has been prepared by the action oi hydroxylamine on benzoyl chloride,2 ethyl benzoate,1,3 or benzamide.4... 

The role played by benzeneseleninic acid or by phenylseleninyl chloride in promoting the rearrangement of A-aryl-benzohydroxamic acids PhOONArOH to p-hydroxy-benzanilides relies on the formation of seleninate or selenenate esters, respectively, followed by Claisen-type shifts to ortho- and then para-positions. ... 

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