Mild arylboronic acid catalyzed selective [4 + 3] cycloadditions: access to cyclohepta[b]benzofurans and cyclohepta[b]indoles

Cao, Kou-Sen; Bian, Hong-Xu; Zheng, Wen‐Hua

doi:10.1039/c5ob00653h

Cited by 35 publications

(12 citation statements)

References 63 publications

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“…3,5-Bis(trifluoromethyl)phenylboronic acid was used as a catalyst to synthesize valuable cyclohepta-[b]benzofurans, cyclohepta[b]benzothiophenes and cyclohepta[b]indoles 6.1c (Scheme 6.1). 111 Syntheses of this scaffold have been previously accomplished by Wu, 78 Winne, 93 Hsung 112 and Li, 113 but this report was one of the first to use boronic acid catalysis. The authors noted that they tested various Lewis and Brønsted acids as well as protic acids with similar pK a values as the boronic acid chosen, but none enabled the desired (4+3)-annulation.…”

Section: Boronic Acid Catalysis and Photocatalysismentioning

confidence: 99%

Recent Advances in Transition-Metal-Free (4+3)-Annulations

et al. 2021

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Abstract(4+3)-Annulations are incredibly versatile reactions which combine a 4-atom synthon and a 3-atom synthon to form both 7-membered carbocycles as well as heterocycles. We have previously reviewed transition-metal-catalyzed (4+3)-annulations. In this review, we will cover examples involving bases, NHCs, phosphines, Lewis and Brønsted acids as well as some rare examples of boronic acid catalysis and photocatalysis. In analogy to our previous review, we exclude annulations involving cyclic dienes like furan, pyrrole, cyclohexadiene or cyclopentadiene, as Chiu, Harmata, Fernándes and others have recently published reviews encompassing such substrates. We will however discuss the recent additions (2010–2020) to the literature on (4+3)-annulations involving other types of 4-atom-synthons.1 Introduction2 Bases3 Annulations Using N-Heterocyclic Carbenes3.1 N-Heterocyclic Carbenes (NHCs)3.2 N-Heterocyclic Carbenes and Base Dual-Activation4 Phosphines5 Acids5.1 Lewis Acids5.2 Brønsted Acids6 Boronic Acid Catalysis and Photocatalysis7 Conclusion

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Section: Boronic Acid Catalysis and Photocatalysismentioning

confidence: 99%

Recent Advances in Transition-Metal-Free (4+3)-Annulations

et al. 2021

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“…In 2015, Zheng and co‐workers reported the first example of arylboronic acid catalyzed [4+3] cycloaddition between indole or benzofuran alcohols 101 and 1,3‐diene 102 (Scheme ) . Catalyst 104 displayed good activity for the reaction and the seven‐membered ring could be constructed under mild conditions.…”

Section: Boron‐based Catalysts For C−c Bond Formationmentioning

confidence: 99%

Boron‐Based Catalysts for C−C Bond‐Formation Reactions

Rao

Kinjo

2018

Chemistry An Asian Journal

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Because the construction of the C-C bond is one of the most significant reactions in organic chemistry, the development of an efficient strategy has attracted much attention throughout the synthetic community. Among various protocols to form C-C bonds, organoboron compounds are not just limited to stoichiometric reagents, but have also made great achievements as catalysts because of the easy modification of the electronic and steric impacts on the boron center. This review presents recent developments of boron-based catalysts applied in the field of C-C bond-formation reactions, which are classified into four kinds on the basis of the type of boron catalyst: 1) highly Lewis acidic borane, B(C F ) ; 2) organoboron acids, RB(OH) , and their ester derivatives; 3) borenium ions, (R BL)X; and 4) other miscellaneous kinds.

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“…Unless otherwise stated, all reagents were purchased from commercial suppliers and used without further purification. Substrates 1 were synthesized according to the literature method. , Analytical thin-layer chromatography (TLC) was performed on silica gel and visualized by irradiation with UV light. For column chromatography, 200–300 mesh silica gel was used.…”

Section: Experimental Sectionmentioning

confidence: 99%

Ag(I)-Promoted Dehydroxylation and Site-Selective 1,7-Disulfonylation of Diaryl(1H-indol-2-yl)methanols

et al. 2018

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A novel dehydroxylation and site-selective 1,7-disulfonylation reaction of diaryl(1 H-indol-2-yl)methanols with sodium sulfinates was described. The protocol provided an efficient strategy for the synthesis of disulfonylated 2-(diarylmethyl)indoles by exploring a range of substrates. The mechanistic studies revealed that silver nitrate served as both a Lewis acid and an oxidant for the sequential 1,7-disulfonylation process leading to the formation of final products.

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Mild arylboronic acid catalyzed selective [4 + 3] cycloadditions: access to cyclohepta[b]benzofurans and cyclohepta[b]indoles

Cited by 35 publications

References 63 publications

Recent Advances in Transition-Metal-Free (4+3)-Annulations

Recent Advances in Transition-Metal-Free (4+3)-Annulations

Boron‐Based Catalysts for C−C Bond‐Formation Reactions

Ag(I)-Promoted Dehydroxylation and Site-Selective 1,7-Disulfonylation of Diaryl(1H-indol-2-yl)methanols

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