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The Additive Pummerer Reaction

Vinylic sulfoxides such as 1 react readily with electrophiles to give highly reactive species, and the overall reactions have been likened to generation of the synthon 2. Treatment of 1 with TFAA, for example, results in what is referred to as an additive Pummerer reaction , and gives the diester 3. Reaction of 1 with triflic anhydride and sodium acetate in acetic anhydride, by contrast, gives an 85% yield of the protected aldehyde 4. [Pg.95]

Based on the concepts of synthon 2 and the additive Pummerer reaction suggest a mechanism for the 1 — 4 transformation. [Pg.95]


The Pummerer rearrangement of sulfoxides with acid anhydrides has been extensively utilized as a method for the synthesis of a-substituted sulfides. When a,(3-unsaturated sulfoxides are used, the initial formed oxysulfonium ion may undergo two different pathways the additive Pummerer reaction or the vinylogous Pummerer reaction. The following sections will consider examples from both pathways. [Pg.196]

The additive Pummerer reaction is a reaction in which displacement of the acyloxy group in the initially formed acyloxysulfonium salt by an internal nucleophile occurs to give a new positively charged sulfur species (Scheme 33). A number of pathways are open for the subsequent reaction of intermediate (138), including elimination of the proton a to the sulfur to give a thionium ion (pathway a), displacement of the sulfur from the a -carbon by an external nucleophile (pathway b), elimination of a 3-proton with formation of an alkene and (139) (pathway c) and loss of a proton fimm the carbon atom a to Nu with formation of (140 pathway d). [Pg.932]

The reactions of 0-carboxyphenyl sulfoxides (95) and sulfoxide (115) encountered earlier (Schemes 21 and 26) are examples of the additive Pummerer reaction in which pathways a and b are operative. [Pg.932]

The first report concerning the additive Pummerer reaction of a,P-unsaturated sulfoxides with dichloroketene appeared in 1981 [220], and work in this area has recently been reviewed [221]. Simple a,P-unsaturated sulfoxides such as (282) react with dichloroketene (generated from the addition of trichloroacetyl chloride to zinc) to produce diastereoisomerically pure c -y-butyrolactones such as (283) (Scheme 5.93) [220]. [Pg.217]

Scheme 20.22 The additive Pummerer reaction, competition with vinylogoiis addition. Scheme 20.23 The additive Pummerer reaction in the synthesis of phakellin skeleton. Scheme 20.24 The interrupted Pummerer reaction. Scheme 20.22 The additive Pummerer reaction, competition with vinylogoiis addition. Scheme 20.23 The additive Pummerer reaction in the synthesis of phakellin skeleton. Scheme 20.24 The interrupted Pummerer reaction.
Scheme 20.22 The additive Pummerer reaction, competition with vinylogous addition. Scheme 20.22 The additive Pummerer reaction, competition with vinylogous addition.
Scheme 20.23 The additive Pummerer reaction in the synthesis of phakellin skeleton. Scheme 20.23 The additive Pummerer reaction in the synthesis of phakellin skeleton.
As depicted in the following scheme, in the presence of sodium iodate and pyridine, several 5,6-dihydroxylated benzofuran derivatives were synthesized via an oxidation-Michael addition of P-dicarbonyl compounds to catechols in a one-pot procedure <06TL2615 06JHC1673>. A novel additive Pummerer reaction of 2-benzo[fc]furan sulfilimines with carbon nucleophiles derived from P-dicarbonyl compounds was also employed to the synthesis of 2,3-disubstituted benzo[b]furans <06TL595>. [Pg.197]

The vinylogous Pummerer reaction of an amido-substituted sulfoxide produces the tetrahydroisoquinoline (Equation 62) <1995JOC7082>. Benzoyltetrahydroisoquinolinones have also been synthesized under Pummerer-type conditions on polymer support <2005H(65)1881>. Additional later examples highlighted the same reaction incorporating a fluorous-phase cyclative-capture method <2005AGE452>. [Pg.237]

For the intramolecular additive Pummerer reaction, following formation of the oxysulfonium ion (211), nucleophilic attack occurs at the electrophilic P-carbon of the 0-activated substrate producing a saturated p-functionalized thionium species (212). Trapping with a second nucleophilic agent affords a product (213) formally derived by sequential attack of two nucleophiles on an abdication (Fig. 10). [Pg.196]

The finding that thionium ions may serve as electrophiles in electrophilic substitution chemistry has greatly extended the synthetic range of the Pummerer reaction. Padwa and Kuethe used intramolecular versions of this process in the preparation of nitrogen-containing heterocycles. Vinyl amido sulfoxide 217 underwent an additive Pummerer reaction, on treatment with triflic anhydride, to yield product 220 (Scheme 56).123 The critical step in this transformation involves a... [Pg.197]

Additive and Vinylogous Additive Pummerer Reactions Sila-Pummerer Reactions Preparation ofTrimethylsiloxy Sulfides The Abnormal Pummerer Reaction... [Pg.909]

Vinyl sulfoxides also partake in additive Pummerer reactions. Of particular interest in this category are cases where the sulfoxide activating agent also provides the internal nucleophile. Two general pathways for such vinylogous additive Pummerer reactions are presented in Scheme 36. ... [Pg.934]

Organic fluorine compounds and methods for their preparation are the central topic of the next four procedures. Much of the synthetic versatility of methyl phenyl sulfone is embodied in FLUOROMETHYL PHENYL SULFONE and the fluoro Pummerer reaction of methyl phenyl sulfoxide with DAST is a key step in its preparation. The utility of this fluoromethyl sulfone in the preparation of fluoroalkenes Is demonstrated in a companion procedure for Z-[2-(FLUOROMETHYLENE) CYCLOHEXYL]BENZENE, a procedure with several prominent stereoselective features. Geminal difluoroalkenes are featured in the following procedure. (3,3 DIFLUOROALLYL)TRIMETHYLSILANE is prepared by a method in which the radical addition of dibromodifluoromethane to alkenes and the selective reduction of a-bromoalkylsilanes are key steps. A procedure for nucleophilic introduction of the trifluoromethyl group completes this set. The key reagent, (TRIFLUOROMETHYL)-TRIMETHYLSILANE is obtained by reductive coupling of TMS chloride and bromotrifluoromethane. Liberation of a CF3- equivalent with fluoride ion in the presence of cyclohexanone affords 1-TRIFLUOROMETHYL-1-CYCLOHEXANOL. [Pg.290]

Additive Pummerer reactions of the type described above using racemic a,P-unsaturated sulfoxides can be accomplished using the following electrophiles acyl chlorides [205,206], dithioacetic acid [207], acetic anhydride [208], mineral acids/alcohols [209], phosphorus pentachloride [210], silyl ketene acetals/zinc iodide [211], thionyl chloride [212], oxalyl chloride [213], trifluoroacetic acid and its anhydride [214-218], triflic anhydride/sodium acetate [219], and dichloroketene (see below). Selected recent examples of work in this area are presented here. [Pg.216]

Applications of the additive mechanism have often remained speculative because both vinylogous and additive pathways can provide the same product and because the preferred mechanism can depend on delicate changes in reaction conditions. Nonetheless, some examples exist in the literature (see next section) concerning the application of additive Pummerer reactions, and we present an innovative application of this Pummerer variant which is preceded by an interrupted Pummerer activation in the next section of this chapter. [Pg.808]

As was introduced earlier in this chapter tScheme 20.22 and previous section), the additive pathway in Pummerer chemistry is in competition with the vinylogous path, and its application is still in some cases unpredictable. Fortunately, Yorimitsu, Oshima, and coworkers have published a sequence of papers providing excellent applications of the additive Pummerer pathway. They used a combination of two Pummerer approaches, such that the activation of sulfoxides was done as usual by an electrophilic reagent, but they used the beginning of a so-called interrupted Pummerer reaction (vide infra) to generate the a,(3-unsaturated sulfonium salt 121. This intermediate did not follow the traditional... [Pg.811]

Scheme 20.27 Additive Pummerer reaction followed by [3,3]-sigmatropic rearrangement. Yorimitsu and Oshima s procedure, with clever modification, has been applied to the S5mthesis... Scheme 20.27 Additive Pummerer reaction followed by [3,3]-sigmatropic rearrangement. Yorimitsu and Oshima s procedure, with clever modification, has been applied to the S5mthesis...
The literature on Pummerer chemistry is quite extensive, and multiple variants are described. However, looking deeply into these alternatives, it becomes apparent that most of them are based on the same principle, and the only variation is the nucleophile source. One example of this is the so-called fluoro-Pummerer reaction, which is in fact a fluoride addition to the normal Pummerer intermediate. The distinguishing feature is the generation of the thionium intermediate, using (diethylamino)sulfur trifluoride (DAST) in combination with metals (Scheme 20.391. DAST is known as a source of nucleophilic fluoride and has been widely used for this purpose. A review on the fluoro-Pummerer reaction was published by Haufe and coworkers in 2012. ... [Pg.819]

Isopropenyl acetate acts as an acetyl transfer reagent in vinylogous additive Pummerer reactions, providing an efficient means for the conversion of vinyl sulfoxides to a-acyl sulfides (167 equation 29). [Pg.936]

The sequence could even be prolonged by including a Pummerer reaction. Thus, treatment of 4-103 with trifluoroacetic acid (TFA) gave the furan 4-104, which underwent a cycloaddition to furnish 4-105 the erythryna skeleton 4-109 was obtained after subsequent addition of a Lewis acid such as BF3- Et20 (Scheme 4.23) [33]. It can be assumed that 4-106, 4-107 and 4-108 act as intermediates. In a more recent example, these authors also used the procedure for the synthesis of indole alkaloids of the Aspidosperma type [34]. [Pg.295]

The mechanism of the formation of compound 67 has been studied by Higa and Krubsack [41] in detail, as shown in Scheme 15. Namely, the initial step of the reaction of the cinnamic acid derivative 66 with thionyl chloride is an electrophilic addition of thionyl chloride across the double bond of cin-namoyl chloride to form the sulfinyl chloride intermediate (66a), which is then converted to 68 by the Pummerer reaction. Dehydrochlorination of 68... [Pg.184]

Suppression of the Pummerer reaction (Fig. 24) could also be a manifestation of the stabilization of the persulfoxide which prevents its interconversion to the hydro-peroxysulfonium ylide, HPSY (Fig. 25), which is the intermediate that has been suggested to undergo a 1,2-shift of the hydroperoxy group and ultimately produces the SC bond cleavage products.92 However, the situation is probably more complex since the intrazeolite reaction of /1-chlorosulfide, 29 (Fig. 28A), requires 7-hydrogen abstraction. The complexation motif (Fig. 28B) which favors the extended rather than folded M+-PS may also play an important role. A complete understanding of these reactions will require additional studies. [Pg.251]

Toru has investigated the stereoselectivity of the conjugate addition of trialkylboranes to 2-arylsulfinylcyclopentenones. Excellent stereocontrol is achieved with different alkyl radicals (Scheme 27) [73-76]. In the acyclic series, the lack of diastereoselectivity in the addition step and a competitive Pummerer rearrangement have limited the synthetic potential of this reaction [77]. [Pg.96]


See other pages where The Additive Pummerer Reaction is mentioned: [Pg.95]    [Pg.217]    [Pg.406]    [Pg.95]    [Pg.217]    [Pg.406]    [Pg.148]    [Pg.224]    [Pg.232]    [Pg.31]    [Pg.644]    [Pg.2285]    [Pg.215]    [Pg.218]    [Pg.807]    [Pg.812]    [Pg.45]    [Pg.185]    [Pg.91]    [Pg.247]    [Pg.569]   


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