Pummerer rearrangements reviews

The best available methods for synthesis of the parent heterocycles are clearly (a) Pummerer rearrangement of thiane 1-oxide, followed by elimination, affording the 3,4-dihydro compound and (b) dehydration of thian-4-ol to give the 3,6-dihydro system (78JHC289). Preparation of the benzannelated compounds is covered in reviews (75AHC(18)59, 80AHC(26)115>. 

Methods for the construction of the thieno[2,3-c]pyridine skeleton based on the formally simultaneous formation of both the pyridine and thiophene rings were documented. Under the Pummerer rearrangement conditions, ( -s ul liny lain idc 222 underwent a cascade transformation into 223, which was oxidized to fused lactam 224 in low yield (1999JOC2038). Data on the use of cascade transformations, including the Pummerer rearrangement - cycloaddition sequence, in the synthesis of complex heterocyclic systems were summarized in a review (1997S1353). 

Pummerer wrote only one further paper on this chemistry, in 1910. The reaction of sulfoxide 11 with acetic anhydride was shown to afford sulfide 12 in what is now recognised as the classical Pummerer rearrangement. From these two reports, the scope of the Pummerer rearrangement has been investigated by many prominent groups who have spent much time and effort in extending the utility of this illustrious reaction. This is perhaps best exemplified by the considerable number of reviews on the Pummerer rearrangement. " ... 

A review of the scope and limitations of fluoro-Pummerer rearrangements, oxidative desulfiirization-fluorination, and oxidative desulfurization-di- and tri-fluorination reactions for the synthesis of fluorinated compounds has been reported. ... 

The one-electron oxidation of iV-benzylphenothiazine by nitric acid occurs in the presence of /i-cyclodextrin, which stabilizes the radical cation by incorporation into its cavity. The reaction is inhibited by adamantane, which preferentially occupies the cavity. Novel Pummerer-type rearrangements of / -sulfinylphenyl derivatives, yielding /7-quinones and protected dihydroquinones, and highly enantioselective Pummerer-type rearrangements of chiral, non-racemic sulfoxides have been reviewed. A comprehensive study has demonstrated that the redox potential for 7- and 8-substituted flavins is linearly correlated with Hammett a values. DFT calculations in [3.3.n]pro-pellanes highlight low ionization potentials that favour SET oxidative cleavage of the strained central C-C bond rather than direct C-H or C-C bond attack. Oxidations and reductions in water have been reviewed. ... 

---