Pummerer rearrangement intramolecular

An intramolecular version of enolate Michael addition to enantiomerically pure vinylic sulfoxides is represented by reaction of a cyclopentenone sulfoxide with dichloroketene (Scheme 5)90 this type of additive Pummerer rearrangement has been developed by Marino and coworkers91 into a highly effective way of constructing variously substituted lactones in very high enantiomeric purity (equation 43). 

Monosulfoxide 13 undergoes the Pummerer rearrangement when treated with acetic anhydride in the presence of sodium acetate.85 The experiments with tetradeuterated and 180-labeled sulfoxide confirm intermediate formation of a dication.86 The ratio of 2,8,8-trideuteriated to 4,4,6,6-tetradeuteriated product 37 is equal to the intramolecular isotope effect ku k0 =1.7 (Scheme 21).85... 

Complexation of sodium to the persulfoxide A (Fig. 13B) appears to inhibit intramolecular hydrogen abstraction to form the hydroperoxy sulfonium ylide (B in Fig. 13A) and allows a direct reaction of 12 with the sodium-complexed persulfoxide, (A in Fig. 13B) to compete. Consistent with this suggestion is the observation that the formation of 13CHO that emanates from the hydroperoxy sulfonium ylide by Pummerer rearrangement and subsequent cleavage is completely suppressed during photo-oxidations of thiolane, 13, in NaMBY ... 

Pyrrolo[2,l-c][l,4]benzothiazepine 297 (R=Ph) has been prepared by an intramolecular nucleophilic displacement of acetyl derivative 296 (Scheme 64 (1992H51)). The same compound and its aryl (R = Ar (1992H51)) and carboethoxy or cyano (R = C(30Et or CN (1990H1291)) analogs can also be obtained by a Pummerer rearrangement-cyclization of sulfinyl precursor 298. 

Cycloadditions of dienes with oxyallyl offer the opportunity to prepare seven-membeted ring systems. This reaction has also proved to be of importance in Ae furan series. A few examples may illustrate the value of this methodology. A tandem Pummerer rearrangement and intramolecular [4-i3]-cycloaddition with a fiiran derivative has been reported <99TL545>. For a similar reaction see <99T13999>. 

Thieno[2,3-c]furans have also been prepared in situ by the Pummerer-rearrangement cyclization reaction (96JOC6166). For transient generation of thieno[2,3-c]furans see also Kuroda et al. [91JCS(CC)1635]. These compounds proved to be reactive intermediates for inter- and intramolecular Diels-Alder reactions (see Section IV). 

A combination of the Pummerer rearrangement and the Ritter reaction occurs in the reaction of acetonitrile with methyl phenyl sulfoxide (equation 25) in a mixture of irifluoroacetic acid and its anhydride, although a substantial amount of the nonnal a-acetoxylation also occurs. Participation by amido groups is also possible, the interest here being largely in the construction of lactams via the intramolecular cycli-zation mode. Whereas Wolfe and his coworkers were unable to find conditions for the cyclization of S-phenylcysteinamide sulfoxides under Pummerer conditions, Kaneko found that variously substituted... 

In the examples of the Pummerer rearrangement presented above, the common feature has been the formation of an a-thiocarbocation, which is then captured either intermolecularly or intramolecularly by a nucleophilic species. There are of course other outlets through which the a-thiocarbocation can pro-... 

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