Enantioselective and Regioselective Ruthenium‐Catalyzed Decarboxylative Etherification of Allyl Aryl Carbonates

Austeri, Martina; Linder, David; Lacour, Jérôme

doi:10.1002/chem.200800619

Cited by 60 publications

(28 citation statements)

References 89 publications

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“…[17] These previous results and new information are summarized in Table 1. For instance, starting from the unsubstituted cinnamyl phenyl carbonate (3a), full conversion was achieved in 2 h and good selectivity levels were measured for the corresponding phenyl ether 4a (b:l ratio > 95:05, ee 84%, entry 1).…”

Section: Resultsmentioning

confidence: 81%

“…[d] Results reported in a preliminary form in ref. [17] cinnamyl moiety was first evaluated. A slight increase of the reaction time was noticed with a para-chlorine atom (2.5 h, 92% conv., entry 2) while a stronger effect was induced by a nitro substituent (7 h, 87% conv., entry 3).…”

Section: Resultsmentioning

confidence: 99%

“…[17] A 1:1 mixture of two differently substituted secondary allylic carbonates (6d, 6e) was treated under our standard catalytic conditions (Scheme 1). At the end of the reaction, 1 H NMR (400 MHz, C 6 D 6 ) analysis showed a statistical mixture of products (4b and 4d) and of cross-over products (4a and 4e).…”

Section: Entrymentioning

confidence: 99%

“…More specifically, the first example of an effective enantioselective decarboxylative allylic etherification was detailed. [17] Our group showed that allyl aryl carbonates are suitable substrates. In the presence of a combination of [18] and readily prepared pyridine monooxazoline (pymox) ligand 2 (Figure 1), [19] the substrates provided, after carbon dioxide extrusion, the corresponding allyl phenyl ethers with high enantiomeric purity and regioselectivity (up to 87% ee and b:l > 20:1).…”

Section: Introductionmentioning

confidence: 99%

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(Cyclopentadienyl)ruthenium‐Catalyzed Regio‐ and Enantioselective Decarboxylative Allylic Etherification of Allyl Aryl and Alkyl Carbonates

2010

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(Cyclopentadienyl)tris(acetonitrile)ruthenium hexafluorophosphate {[CpRu(NCMe)3][PF6]} or (cyclopentadienyl)(η6-naphthalene)ruthenium hexafluorophosphate {[CpRu(η6-naphthalene)][PF6]} in combination with a pyridine oxazoline ligand efficiently catalyze the decarboxylative allylic rearrangement of allyl aryl carbonates. Good levels of regio- and enantioselectivity are obtained. Starting from enantioenriched secondary carbonates, the reaction is stereospecific and the corresponding allylic ethers are obtained with net retention of configuration. An intermolecular version of this transformation was also developed using allyl alkyl carbonates as substrates. Conditions were found to obtain the corresponding products with similar selectivity as in the intramolecular process. Through the use of a hemi-labile hexacoordinated phosphate counterion, a zwitterionic air- and moisture-stable chiral ruthenium complex was synthesized and used in the enantioselective etherification reactions. This highly lipophilic metal complex can be recovered and efficiently reused in subsequent catalysis runs

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Section: Resultsmentioning

confidence: 81%

Section: Resultsmentioning

confidence: 99%

Section: Entrymentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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(Cyclopentadienyl)ruthenium‐Catalyzed Regio‐ and Enantioselective Decarboxylative Allylic Etherification of Allyl Aryl and Alkyl Carbonates

2010

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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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2-[(4S)-4-(1,1-Dimethylethyl)-4,5-dihydro-2-oxazolyl]-pyridine & 2-[(4R)-4-(1,1-Dimethylethyl)-4,5-dihydro-2-oxazolyl]-pyridine

Lacour

Austeri

2012

Encyclopedia of Reagents for Organic Synthesis

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Enantioselective and Regioselective Ruthenium‐Catalyzed Decarboxylative Etherification of Allyl Aryl Carbonates

Cited by 60 publications

References 89 publications

(Cyclopentadienyl)ruthenium‐Catalyzed Regio‐ and Enantioselective Decarboxylative Allylic Etherification of Allyl Aryl and Alkyl Carbonates

(Cyclopentadienyl)ruthenium‐Catalyzed Regio‐ and Enantioselective Decarboxylative Allylic Etherification of Allyl Aryl and Alkyl Carbonates

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

2-[(4S)-4-(1,1-Dimethylethyl)-4,5-dihydro-2-oxazolyl]-pyridine & 2-[(4R)-4-(1,1-Dimethylethyl)-4,5-dihydro-2-oxazolyl]-pyridine

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