Chlorosulphonylation

Reaction with chlorosulphonic acid ( chlorosulphonyl-ation ). Sulphonamides. Many aryl hahdes, either alone or in chloroform solution, when treated with excess of chlorosulphonic acid afford the corresponding sulphonyl chlorides in good yield (compare Section IV.106) the latter may be readily converted into the aryl sulphonamides by reaction with concentrated ammonia solution or with sohd ammonium carbonate. 

The level of chlorination in these materials varies, and influences the properties of the material in exactly the same manner as the closely related chlorinated polyethylene. The introduction of the chlorosulphonyl group in small amounts, <1.5%, gives greater choice in the methods used to crosslink the polymer. However, in general, the properties exhibited by these materials are equivalent to those of chlorinated polyethylene. 

Copper phthalocyanine derivatives are well established as turquoise blue direct and reactive dyes for cellulosic fibres. Chlorosulphonation at the 3-position, followed by hydrolysis, yields sulphonated direct dyes such as Cl Direct Blue 86 (5.32 X = H) and Blue 87 (5.32 X = S03Na). Solubility and dyeing properties can be varied by introducing four chlorosulphonyl groups, some of which are hydrolysed and some converted to sulphonamide by reaction with ammonia or alkylamines. This approach is also the main route to reactive dyes of the copper phthalocyanine type. The reactive system Z is linked to a 3-sulphonyl site... 

Fig. 3.162. Structure of LRSC 9-[(4-chlorosulphonyl)-2-sulphonylphenyl]-3,6-bis(diethyl)amino-xanthylium hydroxide inner salt. Reprinted with permission from S. M. Smith et al. [200].

Aluminium chloride is often used as a Lewis acid catalyst (equations 68 and 69), although there are many other suitable catalysts (equations 70 and 71). Strong electrophiles such as chlorosulphonyl isocyanate or an aluminium salt do not require catalysis (equations 72 and 73). 

The reactions of chiral allylsilanes with electrophiles to give diastereoselective products has recently been extensively reviewed by Masse and Panek166. An example is shown in equation 99. The reaction of the chiral allylsilanes 142 with phenylsulphenyl chloride (PSC) and chlorosulphonyl isocyanate (CSI) takes place with a diastereoselectivity which increases with the increasing steric bulk of the substituent R167. 

Compound (23) (Expt 8.8) is formed by the reaction of but-l-enyl acetate with chlorosulphonyl isocyanate (Section 4.2.17, p. 425).13 The reaction intermediate is the IV-chlorosulphonyl derivative which is subjected to reduction with alkaline sodium sulphide to yield the product which is isolated as a cis trans (1 1) mixture. But-l-enyl acetate is readily synthesised by acetylation of the enol form of butanal. 

General procedure for the reduction of N-chlorosulphonyl /3-lactams with sodium sulphite. A solution of N-chlorosulphonyl /1-lactam dissolved in ether is added slowly to a stirred mixture of about two parts of 25 per cent aqueous sodium sulphite and one part of ether. The aqueous phase is kept slightly basic by addition of 10 per cent potassium hydroxide solution as the reduction proceeds. The reaction course could easily be followed by t.l.c. in which the product has a considerably smaller RF value than the starting material. At the end of the reaction (usually less than 15 minutes) the ether layer is separated and dried and evaporated. The products are of greater than 95 per cent purity as determined by p.m.r. spectroscopy. The reaction may be carried out at 25 °C or at 0°C. 

Reaction of the l-aryl-2-phenacylcyclopropanes with chlorosulphonyl isocyanate and subsequent removal of the chlorosulphonyl group with benzenethiol in pyridine affords the 4,5-dihydro-1,3-oxazepines (91) <95SCI939> and in a reaction sequence in which an aziridine is the source of nitrogen, methyl l-benzyloxycarbonylaziridine-2-carboxylate reacts with 2-(N-benzyl-A -/t /7-butoxycarbonyl)aminoethanol to give the derivative (92) which, after removal of the Boc group, is subject to a reductive cyclisation to yield the hexahydro-l,4-oxazepine (93) <95CPBI 137>. 

Among the procedures which have been developed for /J-lactam syntheses (as reviewed [58] [59]) are the cyclization of /3-haIopropionamides [60] from azetidine-2-carboxylic acids and esters [61] the addition of ketenes to Schiff bases [62] ring-contraction procedures [63] [64] [65] [3+1] cyclizations of a-phenylthioacetamide [66] the cyclization of aminoacids [67], and styrene and N-chlorosulphonyl isocyanate [68]. 

The urea, formed in the reaction of the enamine 344 with chlorosulphonyl isocyanate followed by water, cyclizes to the uracil 345, which lacks substituents on the nitrogen atoms (equation 140)170. 

Cycloadditions of electrophilic olefins or cumulenes to vinylcyclopropanes should also be mentioned in this context, since in most cases stepwise reactions starting with an electrophilic attack are very likely. One example operating with chlorosulphonyl isocyanate and providing a seven-membered lactam is depicted in equation 152 however, so far most reactions in this area have a limited synthetic potential. 

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