1,3-Sulphonyl shift

Attempts to extend this [1,3]-base catalysed process to [1,5] systems, e.g. 73 and 74, result in a series of transmetalations to form the product of a [1,3]-sulphonyl shift (equations 50 and 51)118. 

Intramolecular hydrogen bonds between sulphinyl or sulphonyl groups and hydroxyl groups have also been described106,107. The IR shifts Vjq in these experiments were found at around 1005-1010cm 1108 U0. Several other papers which describe hydrogen bonds of sulphoxides and sulphones are given in References 111-120. 

As already outlined in Chapter 3, the variation in 33S chemical shift with molecular structure has been quite extensively studied in sulphinyl, -SO-, sulphonyl, -S02-, and sulphonic, — SO3, moieties. It has been found that the 33S chemical shift is much more sensitive to structural variation than the chemical shift of other nuclei, such as 13C, 15N or 170. For this reason, 33S NMR is a powerful method for structural elucidation and in many cases a unique probe for assessing the properties of the electronic distribution around the sulphur atom. 

The Russian workers claim that substituents on the azido group which increase the asymmetry, presumably by changing the equivalence of the bonding, shift the bands in question to higher frequency. They also suggest that this asymmetric stretching band for aromatic sulphonyl azides can be correlated by a Hammett Opp relationship where p has a small value. (They find the ultraviolet spectral parameters responding in similar fashion.)... 

The difference of reactivity between neutral and acidic solvents could only lie in the fact that the aromatic sulphonyl chloride is protonated and consequently reduced more easily in its protonated form. A potential shift of about 0.5 V for the main reduction step (Figure 10b) can be observed in the voltammetries. The general Scheme 951 fits the two possible routes according to the acidity of the medium. 

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