General Methodology for the Preparation of Unsymmetrical α-Linked Bisenones via Ligandless Cross-Coupling Reactions

Williams, David R.; Bawel, Seth A.

doi:10.1021/acs.orglett.7b00497

“…Such reaction conditions have commonly been referred to as "ligandless" conditions in other systems. [22][23][24][25][26][27][28] Previously,w ef ound that [PPh 4 ][2]a nd [PPh 4 ] 2 [3] (Scheme 1) could be synthesized by the addition of one and two equivalents of "A gCF 3 "t o1 in the presence of [PPh 4 ]Cl. [29] Thee lectronic properties of 2 and 3 were extensively studied through the use of density functional theory (DFT) calculations,s pectroscopy-oriented configuration interaction (SORCI) calculations,X -ray absorption spectroscopy,a nd cyclic voltammetry.…”

Section: Introductionmentioning

confidence: 99%

Solvated Nickel Complexes as Stoichiometric and Catalytic Perfluoroalkylation Agents**

Shreiber

¹

2021

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The acetonitrile-solvated [(MeCN)Ni(C2F5)3]-was prepared in order to compare and contrast its reactivity with the known [(MeCN)Ni(CF3)3]-towards organic electrophiles. Both [(MeCN)Ni(CF3)3]-and [(MeCN)Ni(C2F5)3]-successfully react with aryl iodonium and diazonium salts as well as alkynyl iodonium salts to give fluoroalkylated organic products. Electrochemical analysis of [(MeCN)NiII(C2F5)3]-suggests that, upon electro-oxidation to [(MeCN)nNi(C2F5)3], reductive homolysis of a perfluoroethyl radical occurs, with the concomitant formation of [(MeCN)Ni(C2F5)2]. Catalytic C-H trifluoromethylations of electron rich arenes were successfully achieved using either [(MeCN)Ni(CF3)3]-or the related [Ni(CF3)4]2-. Stoichiometric reactions of the solvated nickel complexes reveal that "ligandless" nickel is exceptionally capable of serving as reservoir of CF3 anions or radicals under catalytically relevant conditions.File list (2) download file view on ChemRxiv Solvated Nickel.pdf (714.84 KiB) download file view on ChemRxiv Solvated Nickel SI.pdf (1.22 MiB)

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“…Given these considerations, we became interested in developing new fluoroalkylation methods with nickel that employed solvent as the only coordinating ligand. Such reaction conditions have commonly been referred to as “ligandless” conditions in other systems [22–28] …”

Section: Introductionmentioning

confidence: 99%

“…Such reaction conditions have commonly been referred to as "ligandless" conditions in other systems. [22][23][24][25][26][27][28] Previously,w ef ound that [PPh 4 ][2]a nd [PPh 4 ] 2 [3] (Scheme 1) could be synthesized by the addition of one and two equivalents of "AgCF 3 "t o1 in the presence of [PPh 4 ]Cl. [29] Thee lectronic properties of 2 and 3 were extensively studied through the use of density functional theory (DFT) calculations,s pectroscopy-oriented configuration interaction (SORCI) calculations,X -ray absorption spectroscopy,a nd cyclic voltammetry.…”

Section: Introductionmentioning

confidence: 99%

Solvated Nickel Complexes as Stoichiometric and Catalytic Perfluoroalkylation Agents**

Shreiber

¹

2021

Angewandte Chemie

4

0

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The acetonitrile-solvated [(MeCN)Ni(C2F5)3]-was prepared in order to compare and contrast its reactivity with the known [(MeCN)Ni(CF3)3]-towards organic electrophiles. Both [(MeCN)Ni(CF3)3]-and [(MeCN)Ni(C2F5)3]-successfully react with aryl iodonium and diazonium salts as well as alkynyl iodonium salts to give fluoroalkylated organic products. Electrochemical analysis of [(MeCN)NiII(C2F5)3]-suggests that, upon electro-oxidation to [(MeCN)nNi(C2F5)3], reductive homolysis of a perfluoroethyl radical occurs, with the concomitant formation of [(MeCN)Ni(C2F5)2]. Catalytic C-H trifluoromethylations of electron rich arenes were successfully achieved using either [(MeCN)Ni(CF3)3]-or the related [Ni(CF3)4]2-. Stoichiometric reactions of the solvated nickel complexes reveal that "ligandless" nickel is exceptionally capable of serving as reservoir of CF3 anions or radicals under catalytically relevant conditions.File list (2) download file view on ChemRxiv Solvated Nickel.pdf (714.84 KiB) download file view on ChemRxiv Solvated Nickel SI.pdf (1.22 MiB)

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“…Recently, we have reported general methodology for the synthesis of α-linked bisenone systems via a ligandless palladium cross coupling. 8 This reaction facilitates the formation of highly substituted, electron-deficient 1,3-dienes. These dienes undergo regio-and stereocontrolled condensations with indoles to afford complex tetrahydrocarbazoles in a single step via a tandem Michael-Mannich reaction.…”

mentioning

confidence: 99%

IBX Oxidations for the Synthesis of Substituted 2H-Pyrans

Williams¹,

Bawel²,

Haddadpour³

et al. 2021

HETEROCYCLES

2

0

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Facile oxidation of highly substituted 3,5-hexadien-1-ols using 3-iodoxybenzoic acid (IBX) in DMSO has resulted in a one-pot preparation of 2,3,4,6-tetrasubstituted 2H-pyrans.Cycloisomerizations of the 1-oxatriene moiety, produced in the oxidation, spontaneously occur via a disrotatory oxa-electrocyclization. The 2H-pyran products of Table 1 features three differentiated carbonyl substituents. In Celebration of Professor Yasuyuki Kita on His 77th BirthdayThe pyran heterocycle is a common structural motif found within pharmaceuticals, agrichemicals, and biologically active natural products. Several reviews have summarized a variety of techniques for the preparation of substituted pyrans. 1 Methods for the synthesis of tetrahydropyrans have been extensivelyexplored, and we have previously described a general strategy using asymmetric S E ' allylation reactions for enantiocontrolled syntheses of substituted tetrahydropyrans 2,3 Similarly, the formation of dihydropyrans has attracted much attention because these structural motifs also appear within naturally-occurring macrolactones of biological interest. 4 While syntheses of tetrahydropyrans and dihydropyrans are often focused on issues of stereochemistry and efficient strategies for regiocontrolled substitutions, the increased unsaturation of 2H-pyrans results in the characterization of notably less stable species. Successful methods toward substituted derivatives of this reactive family of pyrans are generally limited in scope.In this communication, we report an efficient preparation of 2H-pyrans stemming from 3-iodoxybenzoic acid (IBX) oxidations of highly substituted 3,5-hexadien-1-ols with in situ electrocyclization. The formation of 2H-pyrans via the oxa-electrocyclization reaction has been reported by several investigators in the course of studies for natural product synthesis, 5 and a recent review has compiled key strategies for

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General Methodology for the Preparation of Unsymmetrical α-Linked Bisenones via Ligandless Cross-Coupling Reactions

Cited by 12 publications

References 43 publications

Solvated Nickel Complexes as Stoichiometric and Catalytic Perfluoroalkylation Agents**

Solvated Nickel Complexes as Stoichiometric and Catalytic Perfluoroalkylation Agents**

Solvated Nickel Complexes as Stoichiometric and Catalytic Perfluoroalkylation Agents**

IBX Oxidations for the Synthesis of Substituted 2H-Pyrans

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