A radical/polar crossover annulation between allyl-substituted arenes and electron-deficient alkenes is described. Cobalt-catalyzed hydrogen atom transfer (HAT) facilitates tandem radical C-C bond formation that generates functionalized tetralin products in the face of potentially problematic hydrofluorination, hydroalkoxylation, hydrogenation, alkene isomerization, and radical polymerization reactions. The reactions proceed under mild conditions that tolerate many functional groups, leading to a broad substrate scope. This powerful ring-forming reaction very quickly assembles complex tetralins that are the formal products of the largely infeasible Diels-Alder cycloadditions of styrenes.
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http://dx.doi.org/10.1002/anie.202303228 | DOI Listing |
Chem Commun (Camb)
January 2025
Department of Chemistry, Biochemistry and Pharmaceutical Sciences, University of Bern, Freiestrasse 3, 3012 Bern, Switzerland.
Herein, we present an efficient and practical method for multicomponent carbo-heterofunctionalization of alkenes radical-polar crossover photoredox catalysis. Employing geminal bromonitroalkanes as redox-active reagents with a wide range of O-centered nucleophiles allows rapid access to various 1,3-difunctionalized nitro compounds, including β-nitro ketones, 1,3-nitro alcohols, 1,3-nitro ethers as well as cyclic molecules.
View Article and Find Full Text PDFAngew Chem Int Ed Engl
January 2025
Laboratory of Catalysis and Organic Synthesis, Institute of Chemical Sciences and Engineering, École Polytechnique Fédérale de Lausanne, CH-1015, Lausanne, Switzerland.
The azidofunctionalization of alkenes under mild conditions using commercially available starting materials and easily accessible reagents is reported based on a radical-polar crossover strategy. A broad range of alkenes, including vinyl arenes, enamides, enol ethers, vinyl sulfides, and dehydroamino esters, were regioselectively functionalized with an azide and nucleophiles such as azoles, carboxylic acids, alcohols, phosphoric acids, oximes, and phenols. The method led to a more efficient synthesis of 1,2-azidofunctionalized pharmaceutical intermediates when compared to previous approaches, resulting in both reduction of step count and increase in overall yield.
View Article and Find Full Text PDFAngew Chem Int Ed Engl
December 2024
University of Ottawa, Department of Chemistry and Biomolecular Sciences, 10 Marie Curie, k1n6n5, Ottawa, CANADA.
Hydrosilanes and Lewis bases are known to promote various reductive defunctionalizations, rearrangements, and silylation reactions, facilitated by enigmatic silicon/Lewis base-derived reactive intermediates. Despite the wide variety of transformations enabled by this reagent combination, no examples of intermolecular C(sp3)-C(sp3) forming reactions have been reported. In this work, we've identified 1,1,3,3-tetramethyldisiloxane (TMDSO) and KOtBu as a unique reagent combination capable of generating benzylic nucleophiles in-situ from styrene derivatives, which can subsequently react with alkyl halides to give a new C(sp3)-C(sp3) linkage via formal hydroalkylation.
View Article and Find Full Text PDFJ Am Chem Soc
December 2024
Department of Chemistry, University of Wisconsin─Madison, Madison, Wisconsin 53706, United States.
Herein, we introduce a new platform for alkene carboxy-alkylation. This reaction is designed around CO addition to alkenes followed by radical polar crossover, which enables alkylation through carbanion attack on carbonyl electrophiles. We discovered that CO adds to alkenes faster than it reduces carbonyl electrophiles and that this reactivity can be exploited by accessing CO via hydrogen atom transfer from formate.
View Article and Find Full Text PDFJ Org Chem
December 2024
Department of Organic Chemistry, College of Chemistry, Jilin University, 2699 Qianjin Street, Changchun 130012, P R China.
A catalyst-free reductive radical-polar crossover cyclization with alkenes and sodium dithionite to construct densely functionalized cyclic sultines was described. The key to the success of this practical protocol relies not only on a bifunctional role of sodium dithionite, that is, serving as radical initiator and SO source, but also on the diversified conversions (RPCC/SO insertion/S2 cyclization and RPCC/SO insertion/1,4-addition cyclization processes), which enabled efficient construction of target compounds with the high efficiency and atom- and step-economy under mild conditions.
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