Unlocking Ylide Reactivity in the Metal-Catalyzed Allylic Substitution Reaction: Stereospecific Construction of Primary Allylic Amines with Aza-Ylides

Evans, P. Andrew; Clizbe, Elizabeth A.

doi:10.1021/ja9041302

Cited by 45 publications

(18 citation statements)

References 33 publications

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“…[3a] Furthermore, the synthesis of the corresponding achiral linear products usually use prefunctionalized allylic derivatives with a leaving group under basepromoted or metal-catalyzed conditions. [4] Over the past few decades, allylic substitution [5][6][7][8][9] and allylic oxidation [10] have been the preferred methods for the synthesis of allylic derivatives. Limitations of these approaches include the requirement of a stoichiometric amount of a leaving group or an oxidant, thus making them less attractive in terms of atom economy.…”

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confidence: 99%

“…We then tested a range of achiral bidentate diphosphine ligands with different bite angles. The ligand dppf proved to be superb in terms of the regioselectivity ( Table 1, entry [4][5][6][7][8][9], and a slight excess of benzimidazole (1.2 equiv) led to an increased yield of 89 % with excellent L/B and E/Z selectivity (Table 1, entry 10). Surprisingly, the reaction proceeded smoothly without any additive.…”

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confidence: 99%

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Atom‐Economic, Regiodivergent, and Stereoselective Coupling of Imidazole Derivatives with Terminal Allenes

2014

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New Rh- and Pd-catalyzed regiodivergent and stereoselective intermolecular coupling reactions of imidazole derivatives with mono-substituted allenes are herein reported. Using a Rh(I)/Josiphos system, perfect regioselectivities and high enantiomeric excess were obtained, while a Pd(II)/dppf system gave linear products with high regioselectivities and high E/Z selectivities. This method permits the atom economic synthesis of valuable branched and linear allylic imidazole derivatives.

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confidence: 99%

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Atom‐Economic, Regiodivergent, and Stereoselective Coupling of Imidazole Derivatives with Terminal Allenes

2014

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“…[20][21][22][23][24] The regioselectivities in reactions using rhodium, [25][26][27][28][29][30][31][32][33] iridium, [34][35][36][37][38] and ruthenium [39][40][41] complexes are quite different from those of palladium-catalyzed reaction. Therefore, chiral iridium complexes controlling regio-and enantioselectivities have been a subject of current interest.…”

Section: Resultsmentioning

confidence: 99%

Regio- and Enantioselective Allylic Substitution with Less Active N- or O-Nucleophiles Catalyzed by Iridium-Complex of Bis(oxazolinyl)pyridine

Miyabe

Moriyama

Takemoto

2011

CHEMICAL & PHARMACEUTICAL BULLETIN

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Enantioselective transition metal-catalyzed allylic substitutions have been developed as fundamentally important crosscoupling reactions. [1][2][3][4][5][6][7][8] In general, the heteroatom nucleophiles in these reactions have been largely limited to alkylamines, anilines, carboxylates and phenols. Our laboratory is interested in searching the synthetically useful heteroatom nucleophiles for the synthesis of functionalized allylic compounds (Fig. 1).9) As our successful examples, we have recently reported the utility of oximes 1 and guanidines 5 and 6 as nucleophiles in the transition metal-catalyzed allylic substitution. [10][11][12][13][14] Hydroxylamines are also attractive synthetic reagents for allylic substitution, since they have nitrogen and oxygen atoms as nucleophiles. However, the allylic substitution with hydroxylamines has not been studied well and is limited to a simple palladium-catalyzed amination 15,16) ; thus, there are no reports on asymmetric reactions. We have recently reported that hydroxylamines 2 and 3 having an N-electron-withdrawing substituent, also known as hydroxamic acids, act as reactive oxygen nucleophiles in the enantioselective allylic substitution ( Fig. 1). 17,18) As a part of our program directed toward searching the synthetically useful heteroatom nucleophiles, we describe in detail the study of hydroxylamines 4 as nitrogen nucleophiles in the regio-and enantioselective iridium-catalyzed allylic substitutions. 19) In this study, we also expected that comparison with alkylamines, p-anisidine, and 4-methoxyphenol would lead to informative suggestions regarding the asymmetric reaction using the iridium complex of pybox (bis(oxazolinyl)pyridine) ligand. Results and DiscussionControlling both regio-and enantioselectivities has been of great importance in the allylic substitution of unsymmetrical substrates with heteroatom nucleophiles. [20][21][22][23][24] The regioselectivities in reactions using rhodium, [25][26][27][28][29][30][31][32][33] iridium, [34][35][36][37][38] and ruthenium [39][40][41] complexes are quite different from those of palladium-catalyzed reaction. Therefore, chiral iridium complexes controlling regio-and enantioselectivities have been a subject of current interest. Recently, we reported that the iridium-complex of pybox catalyzed allylic substitution of unsymmetrical substrates to form branched products with good enantioselectivities. 13,14,17,19) Prior to exploring the enantioselective reaction, we first investigated the viability of hydroxylamine 4A having N-benzoyl and O-benzyl groups (Chart 1). Although the reaction of 4A with carbonate 7 was less effective in the absence of a base, the reaction of 4A with acetate 8 proceeded smoothly by employing Et 2 Zn as a base to give the branched product 9Aa in 60% yield without formation of the linear product.Based on these results, we next investigated iridium-catalyzed asymmetric allylic substitution with hydroxylamine 4A under basic conditions (Chart 2). In this study, phosphate 10a was employed as an unsymm...

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“…The aromatic aldehyde 1 reacts with diketone 3 or 5 in the presence of sodium hydroxide to give the Knoevenagel product, the α-ylidene β-diketone A. This reacts instantly with the pyridinium ylide B to form the zwitterionic intermediate C. The intermediate C undergoes cyclization with the elimination of pyridine 20 to give the desired product 4 or 6 in a regio-and diastereoselective manner in a process similar to the Michael-initiated ring-closure reaction.…”

Section: Scheme 1 Proposed Three-component Reaction For the Synthesismentioning

confidence: 99%

Regio- and Diastereoselective Synthesis of trans-2,3-Dihydrofuran Derivatives in an Aqueous Medium

2013

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Unlocking Ylide Reactivity in the Metal-Catalyzed Allylic Substitution Reaction: Stereospecific Construction of Primary Allylic Amines with Aza-Ylides

Cited by 45 publications

References 33 publications

Atom‐Economic, Regiodivergent, and Stereoselective Coupling of Imidazole Derivatives with Terminal Allenes

Atom‐Economic, Regiodivergent, and Stereoselective Coupling of Imidazole Derivatives with Terminal Allenes

Regio- and Enantioselective Allylic Substitution with Less Active N- or O-Nucleophiles Catalyzed by Iridium-Complex of Bis(oxazolinyl)pyridine

Regio- and Diastereoselective Synthesis of trans-2,3-Dihydrofuran Derivatives in an Aqueous Medium

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