Brønsted base-catalyzed annulation of allyl ketones and alkynyl 1,2-diketones

Kong, Xiangbin; Song, Jinshuai; Liu, Jian; Meng, Miao; Yang, Shuang; Zeng, Min; Zhan, Xinyue; Li, Chunsen; Fang, Xinqiang

doi:10.1039/c8cc01020j

Cited by 16 publications

(5 citation statements)

References 38 publications

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“…Alkyne-1,2-diones are of interest for the synthesis of a variety of functionalized and heterocyclic compounds because, as densely functional trielectrophiles (the alkyne, alkynone and dicarbonyl function), they can be easily and selectively transformed by a series of nucleophilic additions, annulations, condensations, and Diels–Alder reactions [ 37 , 38 , 39 , 40 , 41 , 42 , 43 ]. It is highly desirable to develop efficient reaction systems for the synthesis of functionalized pyrazoles from alkyne-1,2-diones and arylhydrazines with high efficiency and regioselectivity under mild reaction conditions.…”

Section: Resultsmentioning

confidence: 99%

Synthesis of Anti-Inflammatory Spirostene-Pyrazole Conjugates by a Consecutive Multicomponent Reaction of Diosgenin with Oxalyl Chloride, Arylalkynes and Hydrazines or Hydrazones

et al. 2021

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Steroid sapogenin diosgenin is of significant interest due to its biological activity and synthetic application. A consecutive one-pot reaction of diosgenin, oxalyl chloride, arylacetylenes, and phenylhydrazine give rise to steroidal 1,3,5-trisubstituted pyrazoles (isolated yield 46–60%) when the Stephens–Castro reaction and heterocyclization steps were carried out by heating in benzene. When the cyclization step of alkyndione with phenylhydrazine was performed in 2-methoxyethanol at room temperature, steroidal α,β-alkynyl (E)- and (Z)-hydrazones were isolated along with 1,3,5-trisubstituted pyrazole and the isomeric 2,3,5-trisubstituted pyrazole. The consecutive reaction of diosgenin, oxalyl chloride, phenylacetylene and benzoic acid hydrazides efficiently forms steroidal 1-benzoyl-5-hydroxy-3-phenylpyrazolines. The structure of new compounds was unambiguously corroborated by comprehensive NMR spectroscopy, mass-spectrometry, and X-ray structure analyses. Performing the heterocyclization step of ynedione with hydrazine monohydrate in 2-methoxyethanol allowed the synthesis of 5-phenyl substituted steroidal pyrazole, which was found to exhibit high anti-inflammatory activity, comparable to that of diclofenac sodium, a commercial pain reliever. It was shown by molecular docking that the new derivatives are incorporated into the binding site of the protein Keap1 Kelch-domain by their alkynylhydrazone or pyrazole substituent with the formation of more non-covalent bonds and have higher affinity than the initial spirostene core.

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Section: Resultsmentioning

confidence: 99%

Synthesis of Anti-Inflammatory Spirostene-Pyrazole Conjugates by a Consecutive Multicomponent Reaction of Diosgenin with Oxalyl Chloride, Arylalkynes and Hydrazines or Hydrazones

et al. 2021

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“…A reaction in which two transiently generated ketone dienolates, each reacting through Cα, are involved in consecutive steps, is reported by Li and Fang (Scheme 29 ). [76] The reaction involves aryl‐substituted allyl ketones 109 and alkynyl‐1,2‐diketones 110 as acceptor under PTC conditions to produce tetrasubstituted cyclopentenones 111 after an intermediate C→O acyl transfer. Attempts to render the process asymmetric by means of chiral ammonium salt C17⋅ Br led to suboptimal enantiocontrol so far.…”

Section: Catalytic Methodsmentioning

confidence: 99%

Extended Enolates: Versatile Intermediates for Asymmetric C‐H Functionalization via Noncovalent Catalysis

Oiarbide

Palomo

2021

Chemistry A European J

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Catalyst-controlled functionalization of unmodified carbonyl compounds is a relevant operation in organic synthesis, especially when high levels of site-and stereoselectivity can be attained. This objective is now within reach for some subsets of enolizable substrates using various types of activation mechanisms. Recent contributions to this area include enantioselective transformations that proceed via transiently generated noncovalent di(tri)enolate-catalyst coor-dination species. While relatively easier to form than simple enolate congeners, di(tri)enolates are ambifunctional in nature and so control of the reaction regioselectivity becomes an issue. This Minireview discusses in some detail this and other problems, and how noncovalent activation approaches based on metallic and metal free catalysts have been developed to advance the field.

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“…Furthermore, control experiment showed that the light is indispensable for the transformation when N,N-dimethylaniline as base (Table 1, entry 10). Examination of light sources was detected under different wavelengths, and the yield ranged from 14% to 34% indicated that the optimal wavelength for this transformation is 460 nm under given conditions (Table 1, entries [11][12]. Finally, replacing B2cat2 by bis(pinacolato)diboron (B2pin2) under identical condition did not obtain any product formation (Table 1, entry 13).…”

Section: Synlett Lettermentioning

confidence: 98%

Photoinduced Metal-Free Arylboration of Unactivated Alkenes: Synthesis of Indoline Boronic Ester

Lu,

He,

Wei

et al. 2023

Synlett

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The environmentally benign synthesis of indoline boronic esters, especially through a way of arylboration to alkenes, remains a challenge due to the use of transition metals or high temperature conditions. We describled a photoinduced metal-free arylboration of unactivated alkenes for the synthesis of indoline boronic esters and 1,2,3,4-tetrahydroquinoline boronic ester in good yields. This approach showed good compatibility and great efficiency for a range of allylphenylamines as well as alkylamine. Remarkably, this transformation also suggested that the base is not necessary for photosensitizer-free diboron reagent-mediated mild generation of aryl radical. Furthermore, compared to previously reported methods, this approach is mild and environmentally benign.

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Brønsted base-catalyzed annulation of allyl ketones and alkynyl 1,2-diketones

Cited by 16 publications

References 38 publications

Synthesis of Anti-Inflammatory Spirostene-Pyrazole Conjugates by a Consecutive Multicomponent Reaction of Diosgenin with Oxalyl Chloride, Arylalkynes and Hydrazines or Hydrazones

Synthesis of Anti-Inflammatory Spirostene-Pyrazole Conjugates by a Consecutive Multicomponent Reaction of Diosgenin with Oxalyl Chloride, Arylalkynes and Hydrazines or Hydrazones

Extended Enolates: Versatile Intermediates for Asymmetric C‐H Functionalization via Noncovalent Catalysis

Photoinduced Metal-Free Arylboration of Unactivated Alkenes: Synthesis of Indoline Boronic Ester

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