Palladium‐Catalyzed Ring‐Opening of 2‐Alkylidenecyclobutanols: Stereoselective Synthesis of γ,δ‐Unsaturated Ketones by C−C Bond Cleavage

Chen, Ling; Sun, Feng‐Na; Sun, Yi; Xu, Zheng; Zheng, Zhan‐Jiang; Cui, Yuming; Cao, Jian; Xu, Li‐Wen

doi:10.1002/adsc.201701078

Cited by 14 publications

(5 citation statements)

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“…The reaction also tolerated a boronic ester substituent on the aryl triflate (16), which, like the bromo example (10), provides a useful handle for further coupling. Heterocyclic triflates, including 2-pyridinyl (17) and 8-quinolinyl triflate (18) were also found to be excellent substrates.…”

Section: Resultsmentioning

confidence: 99%

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Carbopalladation of C–C σ-bonds enabled by strained boronate complexes

2018

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Transition metal-catalysed cross-coupling reactions, particularly those mediated by palladium, are some of the most broadly used chemical transformations. The fundamental reaction steps of such crosscouplings typically include oxidative addition, transmetalation, carbopalladation of a -bond, and/or reductive elimination. Herein, we describe an unprecedented fundamental reaction step: a C−C σ-bond carbopalladation. Specifically, an aryl palladium(II) complex interacts with a −bond of a strained bicyclo[1.1.0]butyl boronate complex to enable addition of the aryl palladium(II) species and an organoboronic ester substituent across a C−C -bond. The overall process couples readily available aryl triflates and organoboronic esters across a cyclobutane unit with total diastereocontrol. The pharmaceutically-relevant 1,1,3-trisubstituted cyclobutane products are decorated with an array of modular building blocks, including a boronic ester which can be readily derivatized.

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Section: Resultsmentioning

confidence: 99%

“…In the context on transition-metal catalysis, the activation of highly strained C−C -bonds has been achieved, 14,15 but is generally limited to oxidative addition 16 and -carbon elimination processes (e.g. the ring-opening of cyclopropylsilyl ethers 17 and cyclobutanols 18 to give alkyl ketones).…”

Section: Introductionmentioning

confidence: 99%

Carbopalladation of C–C σ-bonds enabled by strained boronate complexes

2018

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“…In the ring-opening/coupling reactions of unsymmetrical cyclobutanol derivatives having an sp 2 carbon such as benzocyclobutenol 25 , cyclobutenol 28 , and alkylidenecyclobutanol 31 with aryl bromides, the C(sp 2 )–C(sp 3 ) bond is selectively cleaved because of the facile interaction between the palladium center and the sp 2 carbon (Scheme a–c, respectively). This site-selectivity has been exploited in the synthesis of triphenylene 36 starting from tricyclic benzocyclobutenol 33 and phenyl bromide 4 (Scheme ).…”

Section: Cyclobutanolsmentioning

confidence: 99%

Cleavage of Carbon–Carbon σ-Bonds of Four-Membered Rings

2020

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This article reviews synthetic transformations involving cleavage of a carbon− carbon bond of a four-membered ring, with a particular focus on the examples reported during the period from 2011 to the end of 2019. Most significant is the progress of catalytic reactions involving oxidative addition of carbon−carbon bonds onto transition metals or β-carbon elimination of transition metal alkoxides. When they are looked at from synthetic perspectives, they offer unique and efficient methods to build complex natural products and structures that are difficult to construct by conventional methods. On the other hand, β-scission of radical intermediates has also attracted increasing attention as an alternative elementary step to cleave carbon−carbon bonds. Its site-selectivity is often complementary to that of transition metalcatalyzed reactions. In addition, Lewis acid-mediated and thermally induced ring-opening of cyclobutanone derivatives has garnered renewed attention. On the whole, these examples demonstrate unique synthetic potentials of structurally strained four-membered ring compounds for the construction of organic skeletons.

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“…Thus, identifying a catalytic system which can chemoselectively promote C(sp 2 )–C(sp 3 ) bond activation and C(sp 3 )–C(sp) bond formation and at the same time obtain high enantioselectivity is a formidable challenge. As a continuation of our research on the synthesis and reactions of four-membered rings,26 we report a novel Pd/Cu-catalyzed enantioselective alkyl alkynylation via tandem C(sp 2 )–C(sp 3 ) bond activation/Sonogashira reaction of cyclobutanones with terminal alkynes.…”

Section: Resultsmentioning

confidence: 99%