Benzenesulfonyl chlorides hydroxy

The O-alkyl derivatives of those A-oxides, which exist partly or entirely as (V-hydroxy tautomers, may be made by primary synthesis (as above) or by alkylation. Thus, 5,5-diethyl-1-hydroxybarbituric acid (936 R = H) with methyl iodide/sodium ethoxide gives the 1-methoxy derivative (936 R = Me) or with benzenesulfonyl chloride/ethoxide it gives the alkylated derivative (936 R = PhS02) (78AJC2517). 

Oxetanones can be generally prepared by displacement processes on various /3-substituted carboxylic acids or by halolactonization of /3,y-unsaturated acids. A very general and reliable method consists of treatment of a /8-hydroxy acid with benzenesulfonyl chloride and pyridine at 0°C (equation 91). The yields of /3-lactones are usually in excess of 80% (79JOC356, 74JOC1322). An alternative method involves cyclization of the benzenethiol ester of a /3-hydroxy carboxylic acid by means of mercury(II) methanesulfonate in acetonitrile (equation 92). The yields were excellent in the two cases reported (76JA7874). 

From the beginning of the 1960s, the progress in depsipeptide chemistry was connected with the utilization and further development of the mixed anhydride approach for the initial formation of the ester link between a suitably N-protected amino acid and the hydroxy acid ester. The reagent predominantly applied for the construction of the depsipeptide unit was benzenesulfonyl chloride in pyridine. This reagent, introduced by Shemyakin and co-workers in depsipeptide chemistry, was shown to be an efficient reagent for the formation of the ester bond between a protected amino acid and the hydroxy add component (Scheme 4).[21 22 ... 

Scheme 4 General Route to Protected O-Aminoacyl Hydroxy Acid Esters by the Benzenesulfonyl Chloride Method...

IV-Benzyloxycarbonyl-Substituted Aminoacyl Hydroxy Add ferf-Butyl Esters General Procedure for the Synthesis of Protected Didepsipeptides Using Benzenesulfonyl Chloride 135 ... 

The method of choice, however, is the reaction of (137) with benzenesulfonyl chloride in pyridine at low temperature (equation 49). This conversion proceeds via (138) with strict retention of configuration and is compatible with a variety of substituents (Table 10). ° However, it fails for small substituents (1371 and 137m) in which case only polyesters are formed. In cyclic systems like (140) 3-lactone formation cannot occur if the carboxy and the hydroxy functions are trans (equation SO) In this case the di-... 

Lactones arc conveniently prepared by lactonization of a /1-hydroxy acid with acetic acid431 or phosphorus pentoxide.434-435 in the presence of benzenesulfonyl chloride, cyclization of acid 3 to lactone 4 occurs under basic conditions using pyridine.436... 

Later, the route that employs cyclization of p-hydroxy carboxylic acids under action of benzenesulfonyl chloride and pyridine was used to prepare a series of a,a-difluoro-p-lactones 65 (Scheme 2.30). The compounds 65 were shown to be convenient precursors to the corresponding 1,1-difluoroalkenes 66 afforded in excellent yields by extrusion of CO2 in solution at 150-180°C. 

Benzenesulfonyl chloride added at 10° during 3 hrs. to a soln. of l,l,l-tris(hydroxy-methyl)ethane in pyridine, and stirred 24 hrs. at room temp. -> crude 1,1,1-tris-(benzenesulfonyloxymethyl)ethane (Y 96%) stirred 16 hrs. at 125° under Ng with NaN3 in diethylene glycol l,l,l-tris(azidomethyl)ethane (Y 93%) dis-... 

The action of excess chlorosulfonic acid at room temperaUire on 2,3-, 2,4-, 2,5-, 2,6-, 3,4- and 3,5-dichlorophenols afforded the following substituted benzenesulfonyl chlorides 2,3-dichloro-4-hydroxy 3,5-dichloro-2-hydroxy 2,5-dichloro-4-hydroxy 3,5-dichloro-4-hydroxy 4,5-dichloro-2-hydroxy and 2,6-dichloro-2-hydroxy. The orientation of sulfonation is controlled by the electron-releasing hydroxyl group, so that where possible, sulfonation occurs para... 

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