1,3-sulfonyl shift

More recently, a number of reports dealing with 1,3-sulfonyl shifts which proceed by other mechanisms have been published. For example, Baechler and coworkers suggested that the higher activation enthalpy observed for the isomerization of the deuterium labeled methallyl sulfone 72 in nitrobenzene at 150°C as compared to the corresponding sulfide, together with the positive entropy of activation may be taken as evidence for a homolytic dissociation mechanism (equation 44). A similar mechanism has also been suggested by Little and coworkers for the gas-phase thermal rearrangement of deuterium labelled allyl sec-butyl sulfone, which precedes its pyrolysis to alkene and sulfur dioxide. 

A reaction of 3-(phenylsulfonyl)-l,2-butadiene and diazomethane gave pyrazoline 83 in good yield. Upon irradiation, a 1,3-sulfonyl shift occurred to provide the disub-stituted pyrazole 84 [82]. 

The reaction of enol ethers with allenesulfonamides produces tetrahydropyridines with a novel 1,3-sulfonyl shift <99AG(E)121>. 

Rearrangements of this type are unifold transformations, which show [l.n]shifts of the sulfonyl group within the carbon moiety. 

Reaction products of concomitant anionotropic 1,3-shifts to nitrogen and 1,5-shifts to carbon of sulfonyl groups in azo coupling products ofa-methoxy /J-oxo sulfones have been found under thermal conditions55,56 (equation 14). 

Sulfonanilides suffer 1,3- and 1,5-shifts of the sulfonyl group under various conditions. The reactions may be spontaneous58-60, thermal61,62, photochemical62,63, base-catalyzed61,64,65, acid-catalyzed66-69 or oxidative70 (equation 15). 

The electronic effects of many substituents have been examined by studies of PMR118,119 sulfinyl and sulfonyl groups have been included in some of these. For example, Socrates120 measured the hydroxyl chemical shifts for 55 substituted phenols in carbon tetrachloride and in dimethyl sulfoxide at infinite dilution, and endeavored to... 

Oxygen-17 NMR spectroscopy has an immense potential for structural analysis of cyclic sulfoxides and sulfones as well as for providing insight into the nature of bonding within these two functional groups . Indeed, in addition to data concerning the NMR chemical shifts for several cyclic sulfoxides and sulfones, NMR chemical shift differences between several diastereotopic sulfonyl oxygens in both cyclic and acyclic systems have been reported . 

Although the chemical shifts of most commonly encountered orga-nofluorine compounds are upheld of CFC13 and thus have negative values, there are a number of structural situations for fluorine that lead to positive chemical shifts (downfield from CFC13). These include acyl and sulfonyl fluorides as well as the fluorines of SF5 substituents. 

As indicated in Chapter 2, the single fluorine substituent has an extremely broad range of observed chemical shifts, which include sulfonyl fluorides and acyl fluorides absorbing downfield in the region of +40 and +25 ppm, respectively, all the way up to fluoromethyltrimethylsilane, with its signal far upheld at -277 ppm. 

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