Pummerer-type rearrangement

Pummerer-type rearrangements in synthesis of heterocycles 97YZ282, 98MI62. 

Under the reaction conditions the initially formed thiosulfinate (143) is quantitatively transformed into the disulfide 144 by a Pummerer-type rearrangement. ... 

Another anionic pericyclic domino process is a Pummerer-type rearrangement/... 

Scheme 2.146. Synthesis of several natural products via Pummerer-type rearrangement/ 1,3-dipolar cycloaddition/ring-opening reactions.

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. ... 

The one-pot reaction of the a-(difluoromethyl)-p-sulfinylenamine 70 with trifluoroacetic anhydride in CHCI3, followed by treatment with silica gel affords 4-(difluoromethyl)-5-p-tolylthio-2(3//)-oxazolone 74 (Fig. 5.18). This reaction proceeds via a Pummerer-type rearrangement, followed by [l,3]-proton shift and the simultaneous elimination of trifluoroacetic acid and benzyl alcohol. ... 

In the synthesis of a-amino acids [290] through addition of the carbanion of MMTS to nitriles the overall process involves three other steps frequently encountered in sulfur-mediated chemistry a Pummerer-type rearrangement, with a less common migration of a methylthio group, and a Raney nickel desulfurization following transesterification of the thioester function. 

Methyl carhoxylates.2 The reagent (1) is alkylated by alkyl halides under phase-transfer conditions with NaOH as base. The product is converted to a methyl ester by oxidation followed by a Pummerer-type rearrangement (equation I). 

Sulfoxides,5 Oxidation of sulfides to sulfoxides can be effected with CAN (2 equiv.) in CH2C12/H20 catalyzed by Bu4NBr at 25° (90-100% yields). A Pummerer-type rearrangement does not occur under these conditions. 

The ease of oxidation depends on the electron availability on the sulfur. In quinoline and pyrimidine analogues of (459) the rate of the reaction is decreased, and in these betaine systems sulfone formation is not observed using peracids in the oxidations. A 2-carboxy group as in (463 R = H) promotes the Pummerer-type rearrangement. The initially formed hemimercaptal mainly eliminates water to give the thiazole (464) a minor product (465) may be formed by ring opening (81H(15)1349). 

C. Silicon-Induced Additive Pummerer-Type Rearrangement... 

A. Highly Enantioselective Pummerer-Type Rearrangement Induced by O-Silylated Ketene Acetals... 

The Pummerer-type rearrangement of vinyl sulfoxide has been named an additive Pummerer rearrangement because both the addition to the double bond and the... 

Treatment of a selenoether-based carbohydrate derivative with ozone followed by acetic anhydride led to a mixture of Pummerer-type rearrangement products <2006JA227>. 

The reaction involves a Pummerer-type rearrangement to a a-thiocarbocation, which then reacts with the enol silyl ether. The products can be converted by reduction into 1,4-diketones or by oxidation to unsaturated 1,4-diketones. 

Conceivably, the azo-ir system of II could be derived from the internal redox reaction implied in the elimination-addition sequence depicted in the production of III. Subsequent /3 elimination would afford the desired double bond. In the case of nitrogen as the neighboring atom the ylide intermediate of Scheme 26.1 would not be necessary since the availability of a nonbonding pair of electrons should make the use of base accessory. Thus the reaction pathway would be subsequently shortened. Moreover, the required electrophile, thionyl chloride, would be present in the reaction medium in large quantity. The prospect of a Pummerer-type rearrangement during the transformation of I into II is therefore likely. 

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