Sulphamate esters reactions

Relatively few high yielding and convenient procedures are available for the synthesis of sulphamic esters, but the reaction of alcohols with sulphamoyl chlorides under basic conditions in the presence of a phase-transfer catalyst provides a simple route [32]. When the ratio of alcohol to sulphamoyl chloride is increased to 2 l, the A-alkyl sulphamic ester is produced (Scheme 3.11). 

Doubt has been cast on whether the acylation and sulphonylation of sulphamic esters (Table 5.22) proceeds via a phase-transfer mechanism. The rates of the reactions are enhanced and the reproducibility is increased by the addition of a catalyst, but yields in excess of 75% can be readily attained over an extended reaction time in the absence of the catalyst [46]. 

The synthesis of esters of sulphamic acids is generally achieved by the reaction of the corresponding sulphamoyl halides with an alkoxide or alcohol according to equation 20. A large variety of such esters have been prepared and the synthetic procedures and their properties have been reviewed1. The present work describes the synthetic procedures which have been developed since 1980 to incorporate the sulphamoyl ester moiety (NS03R) into molecules and to look at the general reactivity of sulphamate esters. 

The introduction of the adamantyl group into a sulphamate ester has been achieved by an extension of the reaction in equation 29219. The unsubstituted esters 177a-f were alkylated under solid-liquid (equations 31-34), liquid-liquid (equations 35 and 36) phase transfer catalysis conditions and in a homogeneous medium (equations 37 and 38) by reaction with 1-adamantyl bromomethyl ketone. 

When sulphur trioxide is added to dialkylchloramines R1R2NC1 (220), where R1 = R2 = Et (220a), R1, R2 = (CH2)5 (220b), R1, R2 = 0(CH2CH2)2 (220c), at - 70 °C followed by olefin addition and then allowing the temperature to rise to ambient the process results in the formation of the / -chloroalkyl sulphamate esters 221 (equation 66). The addition across the double bond occurs in accordance with the Markovnikov rule and leads to the trans configuration. This is shown for cyclohexene in equation 67 and the trans structure is confirmed by independent synthesis by reaction of truns-cyclohexanol with... 

The reaction conditions used in the electrophilic addition reactions across olefins to yield the sulphamate esters (equations 65 to 70) involve low temperatures (— 80 °C) and... 

The phase transfer catalysis process has also been extended to synthesize the alkyl and aryl esters (170) of N-aryl sulphamic acids212 (equation 23). If the ratio of aliphatic alcohol (169) to sulphamoyl chloride (168) is increased from 1 1 to 2 1, then N-alkyl-iV-arylsulphamate esters (171) with similar alkyl groups are obtained together with considerable amounts of iV-arylsulphamic acid esters (170). The exclusive formation of the iV-alkyl-iV-arylsulphamate esters (171) can be achieved by employing longer reaction times. A second approach to the synthesis of 171 would be to react the iV-methyl-iV-phenyl sulphamoyl chloride (172) with the alcohol. This was attempted, but the ester failed to form even under forcing conditions. The corresponding AT-alkyl iV-arylsulphamate ion (173) was isolated (equation 24) hydrolysis to the acid was considered to occur as opposed to nucleophilic displacement of the chloride by the methanol. 

Sulphamoyl chloride when reacted with hydroperoxides in the presence of pyridine below — 30 °C leads to the formation of the novel alkyl sulphamoyl peroxides H2NS0200CH2R (R = CH2CH3, CH2CH2CH3) 303 (equation 98)305. Hydrolysis or ammonolysis of these compounds leads to formation of sulphamic acid or sulphamide respectively. 2-Nitrophenylsulphamoyl chloride (304), prepared from the corresponding sulphamic acid by reaction with PC15, has been used to prepare iV-(2-nitrophenyl)-iV -substituted sulphamides (305) and aryl esters (306) (equation 99)306. 

DuBois prepared 2-hydroxyphenyl esters of sulphamic acids by reaction of the appropriate amine with catechol sulphate (see Section III.A, equation 63). The reaction proved sluggish when the amine used was aniline, but work-up of the reaction yielded 28% of the iV,iV -diphenylsulphamide 340, R = Ph346. The formation of 340, is considered to occur due to the low rate of attack by the poorly nucleophilic aniline on 218. 

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