Efficient Generation of Biologically Active <i>H</i>-Pyrazolo[5,1-<i>a</i>]isoquinolines via Multicomponent Reaction

Chen, Zhiyuan; Wu, Jie

doi:10.1021/ol101988q

Cited by 151 publications

(58 citation statements)

References 62 publications

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“…Another example of a base-catalyzed [3+3] cycloaddition of azomethine imines 166 takes place with 1,4-dithiane-2,5-diol 247. DABCO catalyzes this process (Scheme 96) in methanol giving products 248 resulting from the attack of the base to mercaptoacetaldehyde followed by addition to the azomethine imine and subsequent intramolecular cyclization, the diastereoselectivity 66 being controlled by the anomeric effect. 144 Nucleophilic phosphine catalysis has been used for different types of [3+n] cycloaddition of azomethine imines 166 with allenoates 77 (Scheme 98).…”

Section: Scheme 91 No Cation-catalyzed [3+2] Cycloaddition Of Azomethmentioning

confidence: 99%

1,3-Dipolar cycloadditions of azomethine imines

2015

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Azomethine imines are considered 1,3-dipoles of the aza-allyl type which are transient intermediates and should be generated in situ but can also be stable and isolable compounds. They react with electron-rich and electron-poor olefins as well as with acetylenic compounds and allenoates mainly by a [3 + 2] cycloaddition but they can also take part in [3 + 3], [4 + 3], [3 + 2 + 2] and [5 + 3] with different dipolarophiles. These 1,3-dipolar cycloadditions (1,3-DC) can be performed not only under thermal or microwave conditions but also using metallo- and organocatalytic systems. In recent years enantiocatalyzed 1,3-dipolar cycloadditions have been extensively considered and applied to the synthesis of a great variety of dinitrogenated heterocycles with biological activity. Acyclic azomethine imines derived from mono and disubstituted hydrazones could be generated by prototropy under heating or by using Lewis or Brønsted acids to give, after [3 + 2] cycloadditions, pyrazolidines and pyrazolines. Cyclic azomethine imines, incorporating a C-N bond in a ring, such as isoquinolinium imides are the most widely used dipoles in normal and inverse-electron demand 1,3-DC allowing the synthesis of tetrahydro-, dihydro- and unsaturated pyrazolo[1,5-a]isoquinolines in racemic and enantioenriched forms with interesting biological activity. Pyridinium and quinolinium imides give the corresponding pyrazolopyridines and indazolo[3,2-a]isoquinolines, respectively. In the case of cyclic azomethine imines with an N-N bond incorporated into a ring, N-alkylidene-3-oxo-pyrazolidinium ylides are the most popular stable and isolated dipoles able to form dinitrogen-fused saturated and unsaturated pyrazolopyrazolones as racemic or enantiomerically enriched compounds present in many pharmaceuticals, agrochemicals and other useful chemicals.

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Section: Scheme 91 No Cation-catalyzed [3+2] Cycloaddition Of Azomethmentioning

confidence: 99%

1,3-Dipolar cycloadditions of azomethine imines

2015

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“…A four-component reaction of 2-alkynylbenzaldehydes 111, hydrazines 112, methanol, and a,b-unsaturated carbonyl compounds 122 was demonstrated as an efficient protocol to provide compounds 137 in 54-91% yields. [44] The presence of N-heterocyclic carbene (IPr) would promote the formation of 1,2-dihydroisoquinolines 129 through the reaction of 2-alkynylbenzaldehyde hydrazides 15 with a,b-unsaturated aldehydes 118. In the transformation, the corresponding products were afforded in 54-94% yields, and none of the cyclization product was isolated.…”

Section: A C H T U N G T R E N N U N G [3+2] Cyclization Of N-imide Ymentioning

confidence: 99%

N‐Imide Ylide‐Based Reactions: CH Functionalization, Nucleophilic Addition and Cycloaddition

Qiu

Kuang

2014

Adv Synth Catal

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As valuable building blocks for introducing nitrogen, N-imide ylides represent an important class of reactive species and are synthons for the synthesis of nitrogen-containing heterocycles that potentially have biological activities. During the past decades, tremendous efforts have been devoted to the tandem processes involving N-imide ylides as well as their asymmetric applications. In particular, several types of N-imide ylide-based reactions have been established, such as C À H functionalization, nucleophilic addition, and cycloaddition, etc. In this review, recent advances in N-imide ylides chemistry are presented ordered according to the sequence of various reaction types.

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“…1,2 Among groups of isoquinolines, H-pyrazolo[5,1-a]isoquinolines have been recognized as the subjects of in-depth investigation in organic synthesis due to their promising biological activities, such as the inhibitor of PTP1B and CDC25B, TC-PTP. 3 So far, continuous efforts are dedicated for the constructions of these polycyclic compounds. 4 For instance, Wu and co-workers reported the synthesis of H-pyrazolo[5,1-a]isoquinolines via copper(II)-catalyzed oxidative reactions of tertiary amines with N 0 -(2-alkynylbenzylidene) hydrazides in air.…”

Section: Introductionmentioning

confidence: 99%