Abstract Ionic (2 e − ) nucleophilic addition of allylmetal regents to imines dominates the synthesis of homo‐allyl amine; however, single electron (1 e − ) mediated imine allylation with feedstocks butadiene as an alternative allyl source remains unexplored. In this work, we report a conceptually different radical–radical cross‐coupling strategy for the synthesis of a homoallyl amine between an α‐amino alkyl radical and a transient allylic radical. This metal‐free method provided a novel approach for the synthesis of homoallylic amines (>80 examples) from readily available materials with excellent regioselectivity and exceptional broad functional group compatibility.
This work reports the first visible-light mediated cobalt-catalyzed aldehyde allylation with simple alkenes to produce homo-allylic alcohols. This novel strategy directly uses easily available unactivated alkenes as allyl sources instead of pre-synthesized allylic halides.
Abstract The addition of π‐allylmetal complexes to carbonyls is the most important route to homoallylic alcohols. This study reports the first photocatalytic generation of π‐allyltitanium complexes by a radical strategy. This novel strategy enables the three‐component allylation of carbonyls with 1,3‐butadiene, providing rapid access to valuable homoallylic alcohols (over 60 examples). The exceptional regio‐ and diastereoselectivity provided by dual photoredox/Ti catalysis is comparable to that of the Cr‐catalyzed Nozaki–Hiyama–Kishi allylation reaction.
Hantzsch esters (HEs) are widely recognized as sources of hydride ions (H-) and sacrificial electron donors in their ground state. Here, we report the application of HE as a mediator in [2π+2σ] cycloaddition of bicyclo[1.1.0]butanes (BCBs) with alkenes under photo conditions. Through this strategy, various substituted bicyclo[2.1.1]hexanes can be efficiently prepared.
The metal-hydride hydrogen atom transfer (MHAT) method is widely recognized as a powerful technique for functionalizing alkenes. However, its application in the functionalization of industrial feedstock dienes and allenes is relatively rare due to challenges related to chemo-selectivity. In recent studies, Co-porphines have been identified as highly efficient catalysts under photoirradiation for MHAT, demonstrating an exceptional level of chemoselectivity for the functionalization of dienes and allenes, while disregarding other simple olefins present. This novel method enables the selective reductive coupling of pyridines with dienes and the allylation of aldehydes by the combination with Ti catalysis. Mechanistic studies and density functional theory (DFT) calculations support the idea that the non-reversible transfer of hydrogen atoms from cobalt hydride to dienes and allenes, leading to the generation of allyl radicals, is the key step in the catalytic cycle.
Recently, radical difunctionalization of the feedstock 1,3-butadiene has become an attractive strategy for increasing molecular complexity. Herein, we present a novel approach that effectively combines radical thiol-ene chemistry with TiIII catalysis to enable a three-component aldehyde allylation using 1,3-butadiene as an allyl group source under visible light conditions. This sustainable and straightforward method has facilitated the rapid production of diverse allylic 1,3-thioalcohols with exceptional regio- and diastereoselectivity.
Metal-hydride hydrogen atom transfer (MHAT) has been recognized as a powerful method for alkene functionalization; however, photochemical MAT-mediated chemoselective functionalization of dienes remains undeveloped. In this study, we report a radical strategy (1e–) through MHAT using photoredox cobalt and titanium dual catalysis for aldehyde crotylation with butadiene, achieving excellent regio- and diastereoselectivity.
Abstract Natural stilbenes have shown significant potential in the prevention and treatment of diseases due to their diverse pharmacological activities. Here we present a mild and effective Ti-catalyzed intermolecular radical-relay [2σ + 2π] cycloaddition of bicyclo[1.1.0]-butanes and 1,3-dienes. This transformation enables the synthesis of bicyclo[2.1.1]hexane (BCH) scaffolds containing aryl vinyl groups with excellent regio- and trans -selectivity and broad functional group tolerance, thus offering rapid access to structurally diverse stilbene bioisosteres.
Abstract Ionic (2 e − ) nucleophilic addition of allylmetal regents to imines dominates the synthesis of homo‐allyl amine; however, single electron (1 e − ) mediated imine allylation with feedstocks butadiene as an alternative allyl source remains unexplored. In this work, we report a conceptually different radical–radical cross‐coupling strategy for the synthesis of a homoallyl amine between an α‐amino alkyl radical and a transient allylic radical. This metal‐free method provided a novel approach for the synthesis of homoallylic amines (>80 examples) from readily available materials with excellent regioselectivity and exceptional broad functional group compatibility.
Catalytic metal hydride hydrogen atom transfer (MHAT) reactions have proven to be a powerful method for alkene functionalization. This work reports the discovery of Co-porphines as highly efficient MHAT catalysts with a loading of only 0.01 mol % for unprecedented chemoselective allene functionalization under photoirradiation. Moreover, the newly developed bimetallic strategy by the combination of photo Co-MHAT and Ti catalysis enabled the successful carbonyl allylation with a wide range of amino, oxy, thio, aryl, and alkyl-allenes providing expedient access to valuable β-functionalized homoallylic alcohols in over 100 examples with exceptional regio- and diastereoselectivity. Mechanism studies and DFT calculations supported that selectively transferring hydrogen atoms from cobalt hydride to allenes and generating allyl radicals is the key step in the catalytic cycle.
'/%3e%3cuse xlink:href='%23a' transform='rotate(23.036 .093 25.536)'/%3e%3cuse xlink:href='%23a' transform='rotate(45.87 1.273 16.18)'/%3e%3cuse xlink:href='%23a' transform='rotate(69.945 .996 12.078)'/%3e%3cuse xlink:href='%23a' transform='rotate(20.66 -19.689 31.932)'/%3e%3c/svg%3e)