Synthesis of Pyrido[1,2-<i>b</i>]indazoles via Aryne [3 + 2] Cycloaddition with<i>N</i>-Tosylpyridinium Imides

Zhao, Jingjing; Wu, Chao; Li, Pan; Ai, Wenying; Chen, Hongli; Wang, Chaojie; Larock, Richard C.; Shi, Feng

doi:10.1021/jo200863e

Cited by 71 publications

(26 citation statements)

References 41 publications

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“…The successful oxazole formation from ynamides 21a–d with an electronic ‘push‐pull’ substitution pattern contrasts with the known reactions of N ‐acylpyridinium‐ N ‐aminides as 1,3‐C,N dipoles in the presence of dimethyl acetylenedicarboxylate 28. However, the choice of ylide proved critical as in the presence of 6a , 21b reacts to give pyrazolo[1,5‐ a ]pyridine 28 and no oxazole (Scheme ) 31b…”

Section: Resultsmentioning

confidence: 99%

Efficient and Flexible Synthesis of Highly Functionalised 4‐Aminooxazoles by a Gold‐Catalysed Intermolecular Formal [3+2] Dipolar Cycloaddition

2016

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Oxazolesa re important motifs within bioactive and functional materials.C omplex, fully substituteda nd functionalised 4-aminooxazoles are accessed by an efficienti ntermolecular reactionb etween an ynamide and an N-acylpyridinium N-aminide in the presence of ag old catalyst. Thef ormal [3+ +2] dipolar cycloaddition employs an ucleophilic nitrenoid approach to access the 1,3-N,O-dipole character in ac ontrollable fashion.T he selectivity for ac ycloaddition pathwayp rovides as tark contrast against the indiscriminate reactivity of electrophilic acyl nitrenes.P rotocolsf or the formation of acylfunctionalised aminides are reported from accessible precursors including carboxylic estersa nd acids.T he function of these aminides in the oxazole-forming reaction has been exploreda nd it is shown that substantial elaboration is accommodated despite proximity to the reactivec entre.A saresult functional oxazole-based motifs,s uch as chiral oxazoles with biologically pertinent substitution patterns,a re readily accessible.T he use of ynamide types that are unexplored or little used in gold catalysis has been evaluated. Unusual all-heteroatom substitution patterns around the oxazole are shown to be accessible using thio-ynamides.T he studys hows that ac lose stoichiometry of reactantsi ss uitable alongsider elatively low loadings of the bench-stable precatalysts in practicallys traightforward multi-mmol scale reactions.T he efficiency and flexibility of this regioselective intermolecular preparation is demonstrated in the ready synthesis of oxazoles with substantial structural and functional group variation.

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Section: Resultsmentioning

confidence: 99%

Efficient and Flexible Synthesis of Highly Functionalised 4‐Aminooxazoles by a Gold‐Catalysed Intermolecular Formal [3+2] Dipolar Cycloaddition

2016

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“…Inspired by Ellis and Sundberg's work, 16 we envisioned that employing N-sulfonylpyridinium imides 7 as the starting material should lead to a smooth reaction to pyrido [1,2-b]indazoles (8), and hopefully will provide a synthetically useful approach to this scaffold. To our pleasure, we have demonstrated the preliminary success of this proposed approach in an earlier communication, 21 and herein we wish to disclose in full our investigation, including an expansion in the reaction scope.…”

Section: Introductionmentioning

confidence: 82%

Aryne [3 + 2] cycloaddition with N-sulfonylpyridinium imides and in situ generated N-sulfonylisoquinolinium imides: a potential route to pyrido[1,2-b]indazoles and indazolo[3,2-a]isoquinolines

Zhao

et al. 2012

Org. Biomol. Chem.

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The aryne [3 + 2] cycloaddition process with pyridinium imides breaks the aromaticity of the pyridine ring. By equipping the imide nitrogen with a sulfonyl group, the intermediate readily eliminates a sulfinate anion to restore the aromaticity, leading to the formation of pyrido[1,2-b]indazoles. The scope and limitation of this reaction are discussed. As an extension of this chemistry, N-tosylisoquinolinium imides, generated in situ from N'-(2-alkynylbenzylidene)-tosylhydrazides via an AgOTf-catalyzed 6-endo-dig electrophilic cyclization, readily undergo aryne [3 + 2] cycloaddition to afford indazolo[3,2-a]-isoquinolines in the same pot, offering a highly efficient route to these potential anticancer agents.

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“…The 1,3-dipoles of 1 [ 43 ], 2 [ 44 ], 3 [ 45 ] and 4 [ 46 , 47 , 48 , 49 , 50 , 51 ] were synthesized according to the literature methods. The substrates 5a−h were prepared according to the literature procedures [ 36 , 52 , 53 , 54 , 55 , 56 , 57 ].…”

Section: Methodsmentioning

confidence: 99%

Asymmetric Synthesis of Tetrahydroisoquinoline Derivatives through 1,3-Dipolar Cycloaddition of C,N-Cyclic Azomethine Imines with Allyl Alkyl Ketones

Feng

Chen

et al. 2021

Molecules

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[3 + 2] A 1,3-Dipolar cycloaddition of C,N-cyclic azomethine imines with allyl alkyl ketones has been achieved. The reaction proceeds under mild conditions and tolerates a wide range of functional groups. An array of tetrahydroisoquinoline derivatives is generally constructed with good diastereoselectivities and enantioselectivities (up to >25:1 dr, >95% ee). Moreover, the absolute configuration of the product was previously determined by using the quantum electronic circular dichroism calculation and ECD spectrum method.

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Synthesis of Pyrido[1,2-b]indazoles via Aryne [3 + 2] Cycloaddition withN-Tosylpyridinium Imides

Abstract: The [3 + 2] cycloaddition of arynes with N-tosylpyridinium imides, followed by an elimination of Ts(-), affords pyrido[1,2-b]indazoles under mild reaction conditions in good yields.

Cited by 71 publications

References 41 publications

Efficient and Flexible Synthesis of Highly Functionalised 4‐Aminooxazoles by a Gold‐Catalysed Intermolecular Formal [3+2] Dipolar Cycloaddition

Efficient and Flexible Synthesis of Highly Functionalised 4‐Aminooxazoles by a Gold‐Catalysed Intermolecular Formal [3+2] Dipolar Cycloaddition

Aryne [3 + 2] cycloaddition with N-sulfonylpyridinium imides and in situ generated N-sulfonylisoquinolinium imides: a potential route to pyrido[1,2-b]indazoles and indazolo[3,2-a]isoquinolines

Asymmetric Synthesis of Tetrahydroisoquinoline Derivatives through 1,3-Dipolar Cycloaddition of C,N-Cyclic Azomethine Imines with Allyl Alkyl Ketones

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