Strain-Activated Diels–Alder Trapping of 1,2-Cyclohexadienes: Intramolecular Capture by Pendent Furans

Lofstrand, Verner A.; McIntosh, Kyle C; Almehmadi, Yaseen A.; West, F. G.

doi:10.1021/acs.orglett.9b02085

Cited by 30 publications

(47 citation statements)

References 39 publications

(24 reference statements)

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“…This intermediate is of particular interest given that cyclic allenes are emerging as powerful building blocks in modern synthesis and the new conceptual approach described here should lead to further developments in this eld. [32][33][34] Further work on generating and harnessing allenic-rhodium and rhodium-stabilized allene species in catalytic processes is currently underway.…”

Section: Discussionmentioning

confidence: 99%

Rhodium-catalysed tetradehydro-Diels–Alder reactions of enediynes via a rhodium-stabilized cyclic allene

et al. 2020

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Section: Discussionmentioning

confidence: 99%

Rhodium-catalysed tetradehydro-Diels–Alder reactions of enediynes via a rhodium-stabilized cyclic allene

et al. 2020

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“…Cyclic allenes are attractive building blocks because trapping can occur under mild conditions and lead to the formation of two new bonds, with the creation of one or more sp 3 centres [26][27][28][29][30][31] . Moreover, the inherent axial chirality of cyclic allene intermediates and the relatively facile interconversion of enantiomers could provide an opportunity to achieve asymmetric reactions through a dynamic kinetic resolution (DKR) 32 .…”

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confidence: 99%

Intercepting fleeting cyclic allenes with asymmetric nickel catalysis

Yamano

Kelleghan

Shao

et al. 2020

Nature

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Strained cyclic organic molecules, such as arynes, cyclic alkynes and cyclic allenes, have intrigued chemists for more than a century with their unusual structures and high chemical reactivity 1 . The considerable ring strain (30-50 kilocalories per mole) 2,3 that characterizes these transient intermediates imparts high reactivity in many reactions, including cycloadditions and nucleophilic trappings, often generating structurally complex products 4 . Although strategies to control absolute stereochemistry in these reactions have been reported using stoichiometric chiral reagents 5,6 , catalytic asymmetric variants to generate enantioenriched products have remained difficult to achieve. Here we report the interception of racemic cyclic allene intermediates in a catalytic asymmetric reaction and provide evidence for two distinct mechanisms that control absolute stereochemistry in such transformations: kinetic differentiation of allene enantiomers and desymmetrization of intermediate π-allylnickel complexes. Computational studies implicate a catalytic mechanism involving initial kinetic differentiation of the cyclic allene enantiomers through stereoselective olefin insertion, loss of the resultant stereochemical information, and subsequent introduction of absolute stereochemistry through desymmetrization of an intermediate π-allylnickel complex. These results reveal reactivity that is available to cyclic allenes beyond the traditional cycloadditions and nucleophilic trappings previously reported, thus expanding the types of product accessible from this class of intermediates. Additionally, our computational studies suggest two potential strategies for stereocontrol in reactions of cyclic allenes. Combined, these results lay the foundation for the development of catalytic asymmetric reactions involving these classically avoided strained intermediates.

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“…A striking example of cyclic allene chemistry was reported by West and co-workers in 2019, where in situ generated 1,2-cyclohexadienes underwent (4 + 2) cycloaddition with tethered furans to access complex tetracyclic products ( Figure 18 ). 183 Substrates 98 were subjected to TBAF to afford cycloadducts 100 , presumably by way of cyclic allene intermediate 99 . The products contain three stereocenters, set in a relative sense, including a quaternary center.…”

Section: Use Of Strained Cyclic Allenes To Access Polycyclic Scaffoldsmentioning

confidence: 99%

Leveraging Fleeting Strained Intermediates to Access Complex Scaffolds

Anthony

Wonilowicz

McVeigh

et al. 2021

JACS Au

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Arynes, strained cyclic alkynes, and strained cyclic allenes were validated as plausible intermediates in the 1950s and 1960s. Despite initially being considered mere scientific curiosities, these transient and highly reactive species have now become valuable synthetic building blocks. This Perspective highlights recent advances in the field that have allowed access to structural and stereochemical complexity, including recent breakthroughs in asymmetric catalysis.

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Strain-Activated Diels–Alder Trapping of 1,2-Cyclohexadienes: Intramolecular Capture by Pendent Furans

Cited by 30 publications

References 39 publications

Rhodium-catalysed tetradehydro-Diels–Alder reactions of enediynes via a rhodium-stabilized cyclic allene

Rhodium-catalysed tetradehydro-Diels–Alder reactions of enediynes via a rhodium-stabilized cyclic allene

Intercepting fleeting cyclic allenes with asymmetric nickel catalysis

Leveraging Fleeting Strained Intermediates to Access Complex Scaffolds

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