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Abstract Allylation and conjunctive cross‐coupling represent two useful, yet largely distinct, reactivity paradigms in catalysis. The union of these two processes would offer exciting possibilities in organic synthesis but remains largely unknown. Herein, we report the use of allyl electrophiles in nickel‐catalyzed conjunctive cross‐coupling with a non‐conjugated alkene and dimethylzinc. The transformation is enabled by weakly coordinating, monodentate aza‐heterocycle directing groups that are useful building blocks in synthesis, including saccharin, pyridones, pyrazoles, and triazoles. The reaction occurs under mild conditions and is compatible with a wide range of allyl electrophiles. High chemoselectivity through substrate directivity is demonstrated by the facile reactivity of the β‐γ alkene of the starting material, whereas the ϵ‐ζ alkene of the product is preserved. The generality of this approach is further illustrated through the development of an analogous method with alkyne substrates. Mechanistic studies reveal the importance of the dissociation of the weakly coordinating directing group to allow the allyl moiety to bind and facilitate C(sp3)−C(sp3) reductive elimination.
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Cucurbiturils as Reaction Containers for Photocycloaddition of Olefins
Abstract The [2+2] photocycloaddition (PCA [2+2]) of alkenes is one of the most synthetically useful photoreactions. It is a convenient one‐step reaction that is useful for generating substituted cyclobutanes, polymers, and biologically relevant molecules. However, the reaction efficiency is limited by its bimolecular nature requiring encounter between two reactants within the narrow window of excited state lifetime of the photoactive alkene, and competition from the unimolecular photoisomerization. Our groups have utilized macrocyclic cavitands, especially cucurbiturils(CB), to confine two alkene molecules within their cavities and steer them towards a single dimer regio‐ and stereoselectively. Although, primarily the review focuses on photocycloaddition within CBs, such reactions in closely related cavitands such as cyclodextrins (CD) and calixarenes (CA) are also briefly mentioned to provide a comparison with CBs. Studies on photocycloaddition of olefins within CB by other research groups are also briefly highlighted. A mechanistic model, with ability to predict the nature of the dimer product formed within the above reaction containers is included.
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- Award ID(s):
- 1807729
- PAR ID:
- 10048351
- Publisher / Repository:
- Wiley Blackwell (John Wiley & Sons)
- Date Published:
- Journal Name:
- Israel Journal of Chemistry
- Volume:
- 58
- Issue:
- 3-4
- ISSN:
- 0021-2148
- Page Range / eLocation ID:
- p. 264-275
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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