1,4-Sulfonyl migration

A heteroaromatic nucleus can serve also as an acceptor for the migrating sulfonyl group. Thus, irradiation of numerous 4-pyrimidinyl esters of alkyl and aryl sulfonic acids (24) in alcohol with low-pressure mercury arcs readily... 

A highly diastereoselective alkenoylation of protected optically active a-hydroxy- and a-aminoalkanals is achieved with (alkyl-substituted) [1-(diisopropylaminocarbonyloxy)-l-[(4-tnethylphenyl)sulfonyl]-2-alkeuyl]lithium,1 ,2, generated by deprotonation with butyllithi-um in THF. During the reaction, the aminocarbonyl residue migrates and 4-methylbenzenesul-finate is eliminated. 

In allyl sulfones 1,3-migrations of the sulfonyl group take place thermally49 51 or Pd(0)-catalyzed52 (equation 11). 

Rearrangements of nitrones due to migration of the A-oxide oxygen can be induced both, photochemically and by various reagents, but in specific conditions it can proceed spontaneously. On one hand, such transformations are caused by the O-nucleophilic character of nitrones able to react easily with acid anhydrides, their halo anhydrides, sulfonyl chloride and other agents on the other hand, by a significant CH-acidity of a-alkyl groups. 

The method is of general applicability7 for the synthesis of olefins. Other sulfonyl chlorides, RCH2SO2CI, have been used where R = H, C2H5, CeHs, and C6H5CH2 other diazoalkanes that have been used are diazoethane and l-diazo-2-methyl-propane. In all cases the olefins form without double-bond migration. 

Electron-rich alkenes like an enol ether react with N-allenylsulfonamides to assist a 1,3-shift of the sulfonyl group, eventually furnishing formal [4+2]-cycloaddition products, tetrahydropyridine derivatives. The sulfonyl group migrates from the nitrogen to the central allenyl carbon atom [25b, 195]... 

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