Indium-catalyzed synthesis of benzannulated spiroketals by intramolecular double hydroalkoxylation of <i>ortho</i>-(hydroxyalkynyl)benzyl alcohols

Pérez-Guevara, Raquel; Sarandeses, Luis A.; Martı́nez, M. Montserrat; Sestelo, José Pérez

doi:10.1039/d2qo01600a

Cited by 7 publications

(2 citation statements)

References 51 publications

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“…[24][25][26] Moreover, they are known to exhibit similar properties to gold(I) catalysts as soft π Lewis acids. [27][28][29][30][31][32][33] Thus, cross coupling between bromoalkynes and allylsilanes can be catalyzed by both gold(I) and indium(III) salts. [34] However, only an aryl-substituted bromoacetylene was used in this coupling reaction, which involves elimination of the bromine atom.…”

Section: Introductionmentioning

confidence: 99%

“…This means that In(III)‐catalyzed reactions do not need to be performed in the absence of oxygen or water, which could be beneficial in the fine chemicals industry by improving the atom economy and reducing waste [24–26] . Moreover, they are known to exhibit similar properties to gold(I) catalysts as soft π Lewis acids [27–33] . Thus, cross coupling between bromoalkynes and allylsilanes can be catalyzed by both gold(I) and indium(III) salts [34] .…”

Section: Introductionmentioning

confidence: 99%

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Indium(III)‐Catalyzed Haloalkynylation Reaction of Alkynes

Daniels,

Wölper,

Haberhauer

2024

Chemistry A European J

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Green chemistry strives for sustainability at the molecular level and is gaining increasing relevance in the development of chemical reactions. The haloalkynylation reaction is a highly atom–economical C−C coupling reaction that was previously only achieved using transition metal catalysts. It enables the introduction of an alkyne unit and a halogen atom into the target molecule. Herein, we present a haloalkynylation reaction catalyzed by indium(III) halides. The use of indium(III) bromide as a catalyst leads exclusively to the cis addition products with yields up to 86 %. In addition, iodoacetylenes can be applied for the first time for the haloalkynylation reaction of internal alkynes which is an important step forward in the development of industrially relevant and sustainable catalysts. In contrast to gold catalysis, which proceeds via a similar mechanism, the use of alkyl‐substituted haloacetylenes as reagents is also possible. Based on 13C labeling experiments and quantum chemical calculations, we postulate two possible mechanisms for the indium(III)‐catalyzed haloalkynylation reactions.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Indium(III)‐Catalyzed Haloalkynylation Reaction of Alkynes

Daniels,

Wölper,

Haberhauer

2024

Chemistry A European J

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Stereospecific Indium(III)‐Catalysed Tandem Cycloisomerization of Functionalized 1,6‐enynes: Scope and Mechanistic Insights

Pérez‐Guevara,

Sarandeses,

Álvarez

et al. 2024

Adv Synth Catal

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Tandem cycloisomerization reactions of functionalized 1,6‐enynes under indium(III) catalysis are described. This atom‐economic transformation proceeds smoothly with 5‐exo‐dig regioselectivity using commercial In(III) halides and 1,6‐enynes furnished with alcohol, carboxylic acid or amine functional groups to give bicyclic structures in good yields and diastereoselectivities. The reaction with enynals involves a three–step mechanism to give an oxatricycle and a conjugated 1,3‐diene. In the absence of the internal nucleophile the enyne cycloisomerization evolves through a skeletal rearrangement or a cyclopropanation reaction after the regioselective 5‐exo‐dig cyclization. The 1,6‐enyne cycloisomerization is stereospecific and the stereoselectivity appears to be independent of the internal nucleophile. Experimental data support a common reaction mechanism involving an initial alkyne electrophilic π‐coordination of In(III) followed by Markovnikov electrophilic alkene addition and ring‐closure by nucleophilic attack. DFT studies hold up a stepwise mechanism involving the formation of a chiral non‐classical carbocation intermediate that determines the diastereoselectivity of this tandem cycloisomerization reaction.

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Stereodivergent Synthesis of Spiroaminals via Chiral Bifunctional Hydrogen Bonding Organocatalysis

Gayen,

Sar,

Ghorai

2024

Angewandte Chemie

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Spiroaminals represent novel structural motifs prevalent in diverse natural products and biologically active molecules. Achieving their enantioselective synthesis is a highly desirable and challenging task in synthetic endeavors due to their intricate molecular frameworks. Herein, we accomplished the first stereodivergent construction of spiroaminals using chiral bifunctional organocatalyzed intramolecular 1,2‐addition followed by an oxa‐Michael addition cascade in a high atom and step economical pathway. A proper modulation of the cinchona‐derived squaramide catalysts efficiently provided access to all the possible stereoisomers with high yield, diastereoselectivity, and excellent enantioselectivity while displaying a broad substrate tolerance. Additionally, we validated the scalability of the reaction and demonstrated the synthesis of variable spiroaminal scaffolds, confirming the viability of our protocol.

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Indium-catalyzed synthesis of benzannulated spiroketals by intramolecular double hydroalkoxylation of ortho-(hydroxyalkynyl)benzyl alcohols

Abstract: The synthesis of benzannulated spiroketals by a double intramolecular hydroalkoxylation reaction of o-(hydroxyalkynyl)benzyl alcohols under indium(III) catalysis is reported. The reaction proceeds, under mild reaction conditions, using low catalyst loading...

Cited by 7 publications

References 51 publications

Indium(III)‐Catalyzed Haloalkynylation Reaction of Alkynes

Indium(III)‐Catalyzed Haloalkynylation Reaction of Alkynes

Stereospecific Indium(III)‐Catalysed Tandem Cycloisomerization of Functionalized 1,6‐enynes: Scope and Mechanistic Insights

Stereodivergent Synthesis of Spiroaminals via Chiral Bifunctional Hydrogen Bonding Organocatalysis

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