Benzenesulfonyl chloride Beckmann rearrangement

A series of analogues of 2-iminopiperidine have been prepared and have been shown to be potent inhibitors of the human nitric oxide synthase isoforms °. The cyclopentanone oxime 346 was esterified with sodium hydroxide and benzenesulfonyl chloride and the subsequent Beckmann rearrangement afforded the 6-propylvalerolactam 348 as the major product and 3-propylvalerolactam 347 as a minor product (equation 133). The major product was converted into the intended 2-iminopiperidine 349. 

The most important route is the conversion of pyrimidines into 1,3,5-triazines. The first one-step transformation was effected by Taylor and Jefford (62JA3744) by heating the pyrimidine (179) with benzenesulfonyl chloride in pyridine (equation 106). The reaction may be considered as an example of an abnormal Beckmann rearrangement. The mechanism of the reaction of the 4-aminopyrimidine (180) is probably dependent on the nature of the 2-substituent (180, R). If R is an electron-releasing moiety, pathway B seems more likely (Scheme 109). The 4-hydroxypyrimidine (179 R = OH) behaves similarly. Many 2-cyano-1,3,5-triazines may be synthesized by this method. 

Activation of the oxime with benzenesulfonyl chloride or p-toluenesulfonyl chloride leads to sulfonate esters which undergo the Beckmann reaction with or without isolation. - The sulfonate esters also rearrange under mild reaction conditions on silica gel.i Under neutral conditions, lV,A(-carbonyldiimida-zole activates oximes in the presence of allyl bromide, followed by spontaneous Beckmann rearrangement. ... 

The Beckmann rearrangement of oximes to give the corresponding amides (equation 93) is well known and was reviewed in detail328,335. The reaction is usually carried out in the presence of strong acids, although modifications were developed which use much milder conditions, e.g. by application of benzenesulfonyl chloride in alkaline... 

Benzenesulfonyl chloride potassium hydroxide 1,1-Iminocyanides from oximes by Beckmann rearrangement... 

Benzenesulfonyl chloride Second-type Beckmann rearrangement... 

Benzenesulfonyl chloride added dropwise during 1 hr. at -10° to cyclohepta-none oxime and pyridine in dry ethylene chloride, stirred 1 hr. at -10 to 0°, 1-morpholino-l-cyclohexene added, warmed carefully wherupon exothermic Beckmann rearrangement occurs at ca. 20°, after 2 days treated with 50%-acetic acid, and stirred 4hrs. -> 2-(2-oxocyclohexylidene)-l-azacyclooctane (Y 79%) refluxed 5-10 hrs. in 2 iV NaOH until dissolved -> co-amino-7-oxotridecanoic acid (Y 80%). F. e. s. S. Hiinig et al., B. 700, 3039 (1967). 

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