Enantioselective Nitrone Cycloadditions of α,β-Unsaturated 2-Acyl Imidazoles Catalyzed by Bis(oxazolinyl)pyridine−Cerium(IV) Triflate Complexes

Evans, David A.; Song, Hyun‐Ji; Fandrick, Keith R.

doi:10.1021/ol061223i

Cited by 147 publications

(70 citation statements)

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“…[16] Furthermore, 11 was also converted into oxazolidinone 13 by routine operations [18] and the same conclusion was also obtained by comparison of the optical rotation value of 13 and that of the known compound.…”

supporting

confidence: 58%

“…Similar low endo/exo selectivities with the aliphatic alkyl nitrones were observed previously. [16] To determine the absolute configuration of isoxazoline adduct 4, 4c was converted into the previously known compound 8 as shown Scheme 1. Treatment of 4c with benzaldehyde and potassium carbonate in ethanol at room temperature for 2 h afforded enone 7 in 89 % yield.…”

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confidence: 99%

“…[5c] and 14, [16] respectively (Scheme 2). Initially, 11 and 12 were obtained from 4a and 4d by the same routine operations.…”

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confidence: 99%

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Catalytic Asymmetric 1, 3‐Dipolar Cycloaddition Reaction of Nitrones with α′‐Phosphoric Enones by a Chiral Ligand‐ Copper(II) Triflate Complex

2008

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Catalytic Asymmetric 1, 3‐Dipolar Cycloaddition Reaction of Nitrones with α′‐Phosphoric Enones by a Chiral Ligand‐ Copper(II) Triflate Complex

2008

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“…For example, complexes with the general formula Ln(pybox)(A) 3 (A ¼ monodentate anionic ligand) have been shown to catalyze a broad selection of reactions, such as enantioselective Diels-Alder [141] and nitrone cycloadditions [142], Friedel-Craft alkylations [143], asymmetric Mannich-type reactions [144], as well as a variety of ene-reactions [145]. It is important to note that most of these processes are catalyzed by in situ prepared complexes, rather than well-defined species, and thus remain out of the scope of this review.…”

Section: Rare Earth Metal Oxazoline Complexes In Asymmetric Catalysismentioning

confidence: 99%

Rare Earth Pincer Complexes: Synthesis, Reaction Chemistry, and Catalysis

Hänninen

Zamora

Hayes

2015

The Privileged Pincer-Metal Platform: Coordination Chemistry &Amp; Applications

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The research field surrounding rare earth pincer complexes has reached a stage where a comprehensive review about the reactivity and catalytic behavior of these species is justified. In this contribution, we begin with a brief introduction on common strategies for the preparation of rare earth pincer complexes, continuing with a section devoted to the versatile reactivity observed for this class of compound. Thereafter, several types of compounds are discussed, including extremely reactive hydrides, cationic species, and intriguing scandium imido complexes. Finally, the last portion of this chapter sums up the hitherto reported catalytic studies, including discussions on ring-opening polymerization of cyclic esters, polymerization of olefins and hydroamination reactions, as well as several examples of more infrequently encountered catalytic processes.

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“…14 Cleavage of the diazoacetoacetate to the diazoacetate and carboxylic acid, a well-known and widely used transformation, 15 followed by esterification of the resulting carboxylic acid with chiral (S)-1-(1-naphthyl)ethanol formed the β-substituted esters (9) in high yield without loss of chirality. Methylation of the imidazole functional group according to the reported procedure 16 smoothly removed the imidazole and produced chiral diesters 10 in good yield. Comparing the NMR data of compound 10e with reported data for the known (1S,3S)-10e and (1S,3R)-10e 14a Confirmed that the product formed from the Mukaiyama-Michael reaction of 1d with 7e is indeed (5S)-8e.…”

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Highly Enantioselective Catalytic Synthesis of Functionalized Chiral Diazoacetoacetates

Doyle

2011

Angewandte Chemie

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The Michael reaction is one of the most general and versatile methods for carbon-carbon bond formation, 1 and its Mukaiyama-Michael variant provides an efficient strategy for the addition of silyl enol ethers to α,β-unsaturated carbonyl compounds. 2 Catalytic asymmetric reactions with broad variations in α,β-unsaturated carbonyl compounds and chiral catalyst (Lewis acid and Brønsted acid) are well documented, 3,4 and the enantioenriched 1,5-dicarbonyl compounds formed from these reactions have proven to be useful building blocks. However, there has been limited variation in the silyl enol ethers used in these reactions, and none of them have incorporated multiple functional groups.We have recently reported condensation reactions of methyl 3-(trialkylsilanoxy)-2-diazo-3-butenoates (1) in Mukaiyama-aldol, 5 Mukaiyama-Michael, 6 and Mannich 5 processes (Scheme 1) in our efforts to construct functionalized diazo compounds. These reactions are especially facile owing to the stabilization afforded by the diazo functional group to the intermediate formed by electrophilic addition (E + + 1 → 5). The resulting multifunctional diazoacetoacetates have proven to be valuable building blocks for the efficient synthesis of functionally complex organic compounds. 5,7 However, attempts to construct chiral multifunctional diazoacetoacetates have been only moderately successful with the only example being the asymmetric catalytic Mukaiyama-aldol reactions of a limited array of aromatic aldehydes with 1 catalyzed by AgF/(R)-BINAP. 8 We now report the first examples of a broadly applicable, highly enantioselective synthesis of chiral γ-functionalized diazoacetoacetates by catalytic Mukaiyama-Michael addition reactions of 3-(tertbutyldimethylsilyloxy)-2-diazo-3-butenoate 1.A survey of chiral Lewis acids for the direct Mukaiya-maaldol or Mukaiyama Michael reactions of 1 with α,β-unsaturated carbonyl compounds showed limited reactivity and low enantioselectivity. The success of Evans' N-oxazolidinone derivatized α,β-unsaturated carbonyl compounds in chiral Lewis acid catalyzed asymmetric reactions 9 prompted us to

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Enantioselective Nitrone Cycloadditions of α,β-Unsaturated 2-Acyl Imidazoles Catalyzed by Bis(oxazolinyl)pyridine−Cerium(IV) Triflate Complexes

Cited by 147 publications

References 10 publications

Catalytic Asymmetric 1, 3‐Dipolar Cycloaddition Reaction of Nitrones with α′‐Phosphoric Enones by a Chiral Ligand‐ Copper(II) Triflate Complex

Catalytic Asymmetric 1, 3‐Dipolar Cycloaddition Reaction of Nitrones with α′‐Phosphoric Enones by a Chiral Ligand‐ Copper(II) Triflate Complex

Rare Earth Pincer Complexes: Synthesis, Reaction Chemistry, and Catalysis

Highly Enantioselective Catalytic Synthesis of Functionalized Chiral Diazoacetoacetates

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