Sulphamic esters

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). 

Alkylation of sulphamic esters under phase-transfer catalytic conditions (Table... 

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]. 

Some years ago62 Williams demonstrated the existence of the neutral sulphonylamine intermediate [HN=S02] (34) in the hydrolysis of sulphamate esters. In recent work63 on esters he has confirmed the existence of this sulphonylamine and also found evidence for an anionic sulphonylamine (35). 

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. 

The study of the electrophilic addition of activated electrophiles across the alkene functional group by Zefirov and coworkers237 has led to the synthesis of a wide range of sulphamate esters. The general approach involves the insertion of S03 into a weak electrophile which generates an activated electrophile that adds readily across carbon-carbon double bonds of olefins (equation 65). 

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... 

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