Intramolecular acylation of α-sulfinyl carbanions with masked α,β-unsaturated esters: a general strategy to 5-alkylidene-2-cyclopentenones

Pohmakotr, Manat; Thamapipol, Sirinporn; Tuchinda, Patoomratana; Reutrakul, Vichai

doi:10.1016/j.tet.2006.12.036

Cited by 9 publications

(5 citation statements)

References 40 publications

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“…Noting our previous success in the fluoride-catalyzed nucleophilic addition of 1 and CF 3 SiMe 3 to succinic anhydride, 12,17 we reason that fluoride-catalyzed nucleophilic addition of 1 to a maleic anhydride−cyclopentadiene adduct 2 18 and a maleic anhydride−cyclohexadiene adduct 3 18 should proceed with high stereoselectivity to produce the corresponding adducts 4 and 5 (Scheme 1). Stereoselective addition of Grignard reagents (R 1 MgX) to 4 or 5 would provide 6 or 7, which should serve as key compounds for the synthesis of gemdifluoromethylenated cage γ-butyrolactone 8 (6,6-difluorooctahydro-2H-3,5-methanopentaleno [1,6-bc]furan-2-ones) or 9 (7,7-difluorooctahydro-3,6-methanoindeno[1,7-bc]furan-2-(2a 1 H)-ones) through the readily formed gem-difluoromethylene radical upon the reductive cleavage of the PhS−CF 2 bond, followed by intramolecular radical cyclization using Bu 3 SnH/ AIBN.…”

Section: ■ Results and Discussionmentioning

confidence: 85%

“…(d, J = 3.1 Hz), 87.4 (dd, J = 33.1, 22.1 Hz), 53.6, 52.3, 47.0, 46.2, 43.6; 19 F NMR (470 MHz, CDCl 3 ): δ −78.6 (d, J = 208.4 Hz, 1F), −76.9 (dd, J = 208.4, 10.1 Hz, 1F); MS: m/z (% relative intensity) 385 (M + + H,18), 384(M + , 12), 318 (4), 275 (21), 225 (14), 159(100), 77 (20); HRMS (ESI-TOF) calcd for C 22 H 18 F 2 O 2 SNa [M + Na] + 407.0893, found 407.0877.…”

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confidence: 99%

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Synthesis ofgem-Difluoromethylenated Polycyclic Cage Compounds

et al. 2015

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The synthesis of gem-difluoromethylenated polycyclic cage compounds, utilizing PhSCF2SiMe3 as a gem-difluoromethylene building block, is described. The fluoride-catalyzed nucleophilic addition of PhSCF2SiMe3 to both maleic anhydride-cyclopentadiene and maleic anhydride-cyclohexadiene adducts was accomplished with high stereoselectivity to provide the corresponding adducts that were treated with Grignard reagents, followed by acid-catalyzed lactonization to afford the corresponding γ-butyrolactones, each as a single isomer. These γ-butyrolactones underwent intramolecular radical cyclization to give the corresponding tetracyclic cage γ-butyrolactones, which were employed as precursors for the synthesis of gem-difluoromethylenated tetracyclic cage lactols or tetracyclic cage furans, upon treatment with Grignard reagents.

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Section: ■ Results and Discussionmentioning

confidence: 85%

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confidence: 99%

Synthesis ofgem-Difluoromethylenated Polycyclic Cage Compounds

et al. 2015

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“…The use of achiral imines produces a mixture of diastereoisomers, as is indicated by Equation b in Scheme 8.11 [46]. Similar strategies were used in the synthesis of cyanodihydropyridines (Equation d, Scheme 8.10) [51,52]. Intramolecular versions of the addition of sulfinylcarbanions have been also reported and applied to the synthesis of different natural and bioactive compounds.…”

Section: Alkyl Carbanionsmentioning

confidence: 99%

Sulfur‐Bearing Lithium Compounds in Modern Synthesis

Ruano

Parra

Alemán

2014

Lithium Compounds in Organic Synthesis

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Sulfur functions have been widely used for the stabilization of lithium carbanions. Their different oxidation states determine a variety of mechanisms for such stabilization, mainly related with their electronic effects (−I and −M) and associative abilities and also with the relative position of sulfur with respect to the C-Li bond. As additional interest, the sulfur of some of these functions is a stable stereogenic center, and their interactions with prochiral lithium carbanions are able to control the stereochemical course of their reactions with electrophiles, which can be successfully used in asymmetric synthesis. Finally, the chemical versatility of the sulfur functions and their easy elimination under diverse conditions confer to the sulfur-stabilized lithium carbanions a very important role in modern synthetic chemistry. In this chapter, we have organized the information attending to the relative position of the carbanionic center with respect to the sulfur function (α-, β-, and γ-lithiation, see Figure 8.1). Each item has been subdivided according to the nature of the sulfur function stabilizing the carbanion. In this sense, sulfoxides, sulfones, and sulfoximines are the three main functions stabilizing any type of lithium-carbanions, but the thioethers have also been described as stabilizing in αand β-lithiation processes. The fragment connecting S and Li is always formed by carbon atoms, but N is present in some cases of γ-lithiation.This chapter covers the literature of the last 10-12 years concerning the preparation and main synthetic applications of the lithium carbanions stabilized by sulfur functions. In most of the cases, the information that appeared in this century helps understand the role of the sulfur functions in the stabilization of the lithium carbanions, and therefore we have only mentioned, as introduction, the seminal references in the field. However, in those cases where there are few references in the last decade and most of the information has been reported before 2000, we have included and briefly commented on the most significant contributions to be able to understand the interest of such stabilizing functions. During the last decade have appeared excellent revisions concerning the reactivity and structure of lithium carbanions [1], the use of different sulfur functions in asymmetric synthesis [2], as Lithium Compounds in Organic Synthesis: From Fundamentals to Applications, First Edition. Edited by Renzo Luisi and Vito Capriati.

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“…44,57 The thermolysis of five-membered sulfinylcycloketones was already reported. [28][29][30][31][32][33][34][35] While sometimes characterized by a radical mechanism 58 instead of an internal concerted elimination, 57 thermolysis concomitantly releases an enone and a sulfenic acid, the last one could be simply trapped to avoid an α to β sulfoxide migration process 59 and/or an alkene isomerization, thus potentially decreasing the selectivity toward the targeted product (Fig. 4).…”

Section: Mechanism and Computational Srearmentioning

confidence: 99%

“…15,16 The thermolysis of sulfoxides, also known as a thermal desulfinylation reaction, is a thermal syn-elimination which has been widely documented in the literature as a valuable synthetic methodology. [21][22][23][24][25][26][27][28][29][30][31][32][33][34][35] Despite its potential for the production of 1, the thermolysis of sulfoxides requires harsh conditions (high temperatures and long reaction times in batch), which increases the likelihood of product degradation, thermal alkene isomerization, and decreases the selectivity toward the target product. Using selenoxide derivatives instead significantly reduces the activation barrier, yet the toxicity of organoselenium derivatives limits the applicability of such a reaction for pharmaceutical purposes.…”

Section: Introductionmentioning

confidence: 99%