Organocatalytic Enantioselective Vinylogous Pinacol Rearrangement Enabled by Chiral Ion Pairing

Wu, Hua; Wang, Qian; Zhu, Jieping

doi:10.1002/anie.201609911

Cited by 60 publications

(21 citation statements)

References 83 publications

(10 reference statements)

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“…We propose that the asymmetric induction occurs during the 1,2hydride migration. Catalytic enantioselective 1,2migrations of prochiral carbocations have been demonstrated only for the migration of alkyl groups, and often in ring-strain releasing processes (25,26). Such asymmetric 1,2-migrations are difficult because the catalyst must differentiate the prochiral faces of the highly reactive, planar carbocation intermediates.…”

Section: Ofmentioning

confidence: 99%

Anti-Markovnikov alkene oxidation by metal-oxo–mediated enzyme catalysis

Hammer

Kubik

Watkins

et al. 2017

Science

166

128

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Catalytic anti-Markovnikov oxidation of alkene feedstocks could simplify synthetic routes to many important molecules and solve a long-standing challenge in chemistry. Here we report the engineering of a cytochrome P450 enzyme by directed evolution to catalyze metal-oxo-mediated anti-Markovnikov oxidation of styrenes with high efficiency. The enzyme uses dioxygen as the terminal oxidant and achieves selectivity for anti-Markovnikov oxidation over the kinetically favored alkene epoxidation by trapping high-energy intermediates and catalyzing an oxo transfer, including an enantioselective 1,2-hydride migration. The anti-Markovnikov oxygenase can be combined with other catalysts in synthetic metabolic pathways to access a variety of challenging anti-Markovnikov functionalization reactions.

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Section: Ofmentioning

confidence: 99%

Anti-Markovnikov alkene oxidation by metal-oxo–mediated enzyme catalysis

Hammer

Kubik

Watkins

et al. 2017

Science

166

128

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“…Thea bsolute configuration of 2a was determined by X-ray crystallography, [18] and the configurations of the other b,g-unsaturated ketones were assigned accordingly. Recrystallization (CH 2 Cl 2 /MeCN) furnished the desired product in enantiopure form.…”

Section: Angewandte Chemiementioning

confidence: 99%

“…Recrystallization (CH 2 Cl 2 /MeCN) furnished the desired product in enantiopure form. Thea bsolute configuration of 2a was determined by X-ray crystallography, [18] and the configurations of the other b,g-unsaturated ketones were assigned accordingly.…”

mentioning

confidence: 99%

Organocatalytic Enantioselective Vinylogous Pinacol Rearrangement Enabled by Chiral Ion Pairing

Wu,

Wang,

Zhu

2016

Angewandte Chemie

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An enantioselective pinacol rearrangement of functionalized (E)-2-butene-1,4-diols was developed. In the presence of a catalytic amount of a chiral BINOL-derived N-triflyl phosphoramide, these 1,4-diols rearranged to b,g-unsaturated ketones in excellent yields and enantioselectivities. The formation of a chiral ion pair between the intermediary allylic cation and the chiral phosphoramide anion was postulated to be responsible for the highly efficient chirality transfer. These chiral building blocks were further converted into enantioenriched polysubstituted tetrahydrofuran and tetrahydronaphthalene derivatives.Pinacol rearrangements, which convert 1,2-diols into ketones under acidic conditions, are a blueprint for a group of carbenium-based molecular reorganization processes.[1] As such reactions generate a new stereogenic center, the ability to control the stereochemical outcome would significantly expand their synthetic utility. However, several factors intrinsic to the reaction mechanism have made this endeavor highly demanding. First, the regioselective generation of one of the two possible carbenium intermediates under strongly acidic conditions is difficult. Second, differentiation of the prochiral faces of highly reactive planar carbocation intermediates is a formidable challenge as it falls out of the reach of typical Lewis acid and Brønsted acid catalysis. As a matter of fact, Antillas chiral phosphoric acid (CPA) catalyzed rearrangement of indolyl diols is the only example of an enantioselective pinacol rearrangement to date (Scheme 1 a).[2] In this transformation, the benzylic cation is generated regioselectively and stabilized in the form of conjugated iminium species A, [3] thereby facilitating the transfer of chiral information. Indeed, imines are the most widely exploited substrates in CPA-catalyzed asymmetric transformations. [4,5] To circumvent the aforementioned challenges, a number of efficient catalytic enantioselective semipinacol rearrangements have been developed. [6][7][8] Two key structural elements have been strategically incorporated into the substrates of these reactions in order to a) regioselectively generate the cationic intermediate or its equivalent and b) render the 1,2-CÀC bond shift a ring-strain-releasing process (Scheme 1 b). While the synthetic significance of these transformations is self-evident, constraints imposed on the substrate structure have nevertheless limited the full exploitation of the pinacol rearrangement. In connection with our ongoing studies of organocatalytic enantioselective transformations, [9] we became interested in the chiral contact ion pairs [10] formed between a CPA and cationic intermediates other than iminium species, [11,12] and we chose allylic cations [13] as our playground. We herein report a catalytic enantioselective vinylogous pinacol rearrangement of 1,4-diols 1 to b,gunsaturated ketones 2 (Scheme 1 c) and provide evidence that supports the hypothesis that chiral allylic contact ion pair B is a key intermediate for the transfer ...

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“…Among all organic reactions, rearrangements are an exciting class of transformations where unusual or even unexpected products can be obtained. Many rearrangements are of practical use in synthetic organic chemistry, including Beckmann [1][2][3][4], Claisen [5][6][7][8], pinacol [9][10][11][12], Wagner-Meerwein [13][14][15][16], Curtius [17][18][19][20], Hofmann [21][22][23][24], Overmann [25][26][27][28] rearrangements, and many others. In organophosphorus chemistry, rearrangements are less developed transformations, however, some examples can be found in the literature (Scheme 1).…”

Section: Introductionmentioning

confidence: 99%

[1,3]/[1,4]-Sulfur atom migration in β-hydroxyalkylphosphine sulfides

Włodarczyk

Borowski

Stankevič

2020

Beilstein J. Org. Chem.

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β-Hydroxyalkylphosphine sulfides undergo [1,3]- or [1,4]-sulfur atom phosphorus-to-carbon migration in the presence of Lewis or Brønsted acids. The direction of sulfur atom migration depends on the type of acid used for the reaction. In the presence of a Brønsted acid, mainly [1,3]-rearrangement is observed, whereas a Lewis acid catalyzes the [1,4]-sulfur migration. To gain insight into the mechanism of these transformations, the stereochemistry of these rearrangements have been tested, along with the conduction of some control experiments and DFT calculations.

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Organocatalytic Enantioselective Vinylogous Pinacol Rearrangement Enabled by Chiral Ion Pairing

Cited by 60 publications

References 83 publications

Anti-Markovnikov alkene oxidation by metal-oxo–mediated enzyme catalysis

Anti-Markovnikov alkene oxidation by metal-oxo–mediated enzyme catalysis

Organocatalytic Enantioselective Vinylogous Pinacol Rearrangement Enabled by Chiral Ion Pairing

[1,3]/[1,4]-Sulfur atom migration in β-hydroxyalkylphosphine sulfides

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