Coupling reactions Methanesulfonyl chloride

Intermediate 10 must now be molded into a form suitable for coupling with the anion derived from dithiane 9. To this end, a che-moselective reduction of the benzyl ester grouping in 10 with excess sodium borohydride in methanol takes place smoothly and provides primary alcohol 14. Treatment of 14 with methanesulfonyl chloride and triethylamine affords a primary mesylate which is subsequently converted into iodide 15 with sodium iodide in acetone. Exposure of 15 to tert-butyldimethylsilyl chloride and triethylamine accomplishes protection of the /Mactam nitrogen and leads to the formation of 8. Starting from L-aspartic acid (12), the overall yield of 8 is approximately 50%, and it is noteworthy that this reaction sequence can be performed on a molar scale. 

Reports on the preparation and use of type I fused-ring aziridinium ions is significantly less than that of the corresponding aziridine. A couple of examples have been reported. A typical method for the synthesis of an aziridinium ion and subsequent reaction with (i )-l,l -binaphthol has been reported <2004TA3847>. The plan here was to carry out an enantioselective reaction between aziridinium 232 and binaphthol. The aziridinium 232 was prepared by treating racemic aminoalcohol 231 with methanesulfonyl chloride and triethylamine. As is usually done, the aziridinium is not isolated but the binaphthol is simply added to the reaction. A 60% yield of (—)-(R,R,R)-233 was isolated along with 30% of a 1 1 mixture of the (R,R,R)- and (R,A,A)-diastereomers (Scheme 40). 

When methanesulfonyl chloride was allowed to react with 2,3,4,6-tetra-O-ben-zylglucopyranose and collidine in dichloromethane, the a-glucopyranosyl chloride was isolated regardless of whether the quaternary ammonium bromide was included. Addition of methanol to the reaction mixture resulted in the formation of an anomeric mixtiue of methyl glycosides. Similar results were obtained with toluenesulfonyl chloride, although it was noted that the initial sulfonylation was somewhat slower [8,9]. The use of tosyl chloride in the dehydrative coupling of alcohols with pyranoses was later revisited by Szeja and his coworkers, with the difference that aqueous... 

Apart from aryl halides, other very easily available substrates for nickel-catalysed biaryl (II) synthesis are aryl sulfonates (XII). Method D is very efficient in the homocoupling reactions of substituted aryl sulfonates in good to excellent yields [15], Table 6. Substituted aryl sulfonates are readily obtained from phenols and trifluoromethanesulfonic anhydride, benzenesulfonyl-, tosyl- or methanesulfonyl chloride in pyridine, or in a suitable inert solvent such as dichloromethane in the presence of triethylamine or Hiinig s base. Among other nickel complexes, Ni(dppe)Cl2 and Ni(dppf)Cl2 have been used (10 mo1%) as slightly less versatile catalysts for the homo-couplings of naphthyl sulfonates in refluxing THF, DMF or their mixtures [42]. 

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