Transition-metal-free base catalyzed intramolecular cyclization of 2-ynylphenols for efficient and facile synthesis of 2-substituted benzo[<i>b</i>]furans

Liu, Yong; Lü, Tao; Tang, Weifang; Gao, Jian

doi:10.1039/c8ra03882a

Cited by 22 publications

(25 citation statements)

References 52 publications

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“…The Sonogashira coupling of 9 with 1‐hexyne gave diyne 10 , and the subsequent removal of the acetyl groups with K 2 CO 3 and MeOH at 0 °C gave diol 11 in 22 % yield. In this deprotection step, the use of NaOH or hydrazine and/or reactions at room temperature resulted in lower yields of 11 due to the formation of the undesired benzofuran derivative through 5‐endo cyclization [22] . Similarly, diol 16 was synthesized in four steps from naphthalene‐2,6‐diol ( 12 ) via dibromide 13 , diacetate 14 , and diyne 15 under almost the same reaction conditions as the synthesis of diol 11 .…”

Section: Resultsmentioning

confidence: 99%

Synthesis of Cyclophenacene‐ and Chiral‐Type Cyclophenylene‐Naphthylene Belts

et al. 2022

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We report the synthesis of a [20]cyclophenacene‐type cyclophenylene‐naphthylene (CPN) belt and the enantioselective synthesis of chiral‐type CPN belts (up to >99 % ee) by the cationic rhodium(I)‐catalyzed intramolecular [2+2+2] cycloaddition of naphthalene‐embedded cyclic polyynes. The synthesis of a depth‐expanded CPN belt was also attempted, but the final intramolecular [2+2+2] cycloaddition was unsuccessful. Theoretical calculations clarified that the reactivity depends on the stability of the transition state in the initial oxidative cycloaddition step which is subject to molecular strain. The cylindrical structures of these CPN belts were confirmed by X‐ray crystallographic analyses. As a result of π‐extension through the introduction of naphthalenes in the chiral‐type CPN belts, the anisotropy dissymmetry factors of electronic circular dichroism and circularly polarized luminescence are amplified compared with the corresponding zigzag‐type chiral cyclophenylene belts.

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Section: Resultsmentioning

confidence: 99%

Synthesis of Cyclophenacene‐ and Chiral‐Type Cyclophenylene‐Naphthylene Belts

et al. 2022

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“…Transition metal-free, base-catalyzed intramolecular hydroalkoxylation of o-alkynyl phenols 18 was studied by Gao and co-workers for the rapid synthesis of benzofuran derivatives 19 in good yield (Scheme 10). [26] Various o-alkynyl phenols were treated with 10 mol% of Cs 2 CO 3 in CH 3 CN to furnish corresponding benzofuran derivatives. In general, it was observed that electron-rich aryl/aliphatic alkyne (R 2 = aryl ring with the electron-releasing group or alkyl) offered the corresponding furan in excellent yield.…”

Section: Base Catalyzed/promoted Intramolecular Hydroalkoxylationmentioning

confidence: 99%

Metal‐Free Intramolecular Hydroalkoxylation of Alkyne: Recent Advances

Nanda

2021

ChemistrySelect

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Dedicated to Professor Sundarbabu BaskaranHydroalkoxylation of alkyne offers a unique platform to rapidly access structurally complex and densely functionalized oxygenbearing heterocycles. Further, to enhance the synthetic utility, various cascade reactions including hydroalkoxylation have been reported in both stereo-as well as enantioselective manner under metal and metal-free conditions. A collection of the most representative and recent methods employing metalfree hydroalkoxylation events are presented in this review article. Organocatalytic Intramolecular Hydroalkoxylation CascadeUndoubtedly, organocatalytic Michael addition reaction has come fore as one of the powerful methods for the formation of CÀ C, CÀ N, and CÀ O bonds. [12] In this context, nitroenynes have

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“…CD intensity of 1 gradually decreased with time and disappeared after 72 h, while the half of that remained in 2 . o ‐Alkynyl phenol derivatives were known to form benzofuran rings under basic conditions [11] . For pyridine‐acetylene‐aniline structures, a similar decomposition to indole might occur slowly.…”

Section: Figurementioning

confidence: 99%

A Pyridine‐Acetylene‐Aniline Oligomer: Saccharide Recognition and Influence of this Recognition Array on the Activity as Acylation Catalyst

2020

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In order to create new functions of foldamer‐type hosts, various kinds of recognition arrays are expected to be developed. Here, a pyridine‐acetylene‐aniline unit is presented as a new class of a saccharide recognition array. The conformational stabilities of this array were analyzed by DFT calculation, and suggested that a pyridine‐acetylene‐aniline oligomer tends to form a helical structure. An oligomer of this array was synthesized, and its association for octyl β‐D‐glucopyranoside was confirmed by 1H NMR measurements. UV/Vis, circular dichroism, and fluorescence titration experiments revealed its high affinity for octyl glycosides in apolar solvents (Ka=104 to 105 M−1). This oligomer was relatively stable under basic conditions, and therefore this array was expected to be applied to the derivatization of saccharides. A 4‐(dialkylamino)pyridine attached pyridine‐acetylene‐aniline oligomer proved to catalyze the acylation of the octyl glucoside.

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Transition-metal-free base catalyzed intramolecular cyclization of 2-ynylphenols for efficient and facile synthesis of 2-substituted benzo[b]furans

Abstract: An efficient and practical transition-metal-free synthesis of 2-substituted benzo[b]furans catalyzed by readily accessible base was developed with broad substrates scope.

Cited by 22 publications

References 52 publications

Synthesis of Cyclophenacene‐ and Chiral‐Type Cyclophenylene‐Naphthylene Belts

Synthesis of Cyclophenacene‐ and Chiral‐Type Cyclophenylene‐Naphthylene Belts

Metal‐Free Intramolecular Hydroalkoxylation of Alkyne: Recent Advances

A Pyridine‐Acetylene‐Aniline Oligomer: Saccharide Recognition and Influence of this Recognition Array on the Activity as Acylation Catalyst

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