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Keywords = organocatalyzed cycloadditions

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16 pages, 1864 KiB  
Article
Organocatalyzed Enantioselective [3+2] Cycloaddition Reactions for Synthesis of Dispiro[benzothiophenone-indandione-pyrrolidine] Derivatives
by Hong-Yan Liu and Da-Ming Du
Molecules 2024, 29(20), 4856; https://doi.org/10.3390/molecules29204856 - 13 Oct 2024
Viewed by 1452
Abstract
An organocatalytic enantioselective [3+2] cycloaddition reaction involving 2-arylidene-1,3-indandiones and N-2,2-difluoroethylbenzothiophenone imines was developed. This approach efficiently afforded dispiro[benzothiophenone-indandione-pyrrolidine]s, featuring three stereocenters, in 84–98% yields with 3–93% ee and 9:1–>20:1 dr. Notably, the method maintained its yield and enantioselectivity integrity even in a [...] Read more.
An organocatalytic enantioselective [3+2] cycloaddition reaction involving 2-arylidene-1,3-indandiones and N-2,2-difluoroethylbenzothiophenone imines was developed. This approach efficiently afforded dispiro[benzothiophenone-indandione-pyrrolidine]s, featuring three stereocenters, in 84–98% yields with 3–93% ee and 9:1–>20:1 dr. Notably, the method maintained its yield and enantioselectivity integrity even in a gram-scale amplification experiment. For example, the product with substituents on aromatics were obtained in 90% yield with 91% ee and >20:1 dr. Its absolute configuration was established through X-ray single-crystal diffraction analysis, and a plausible reaction mechanism was proposed. Full article
(This article belongs to the Special Issue Advances in Asymmetric Tandem Reactions)
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31 pages, 8603 KiB  
Review
Synthesis of Non-Racemic Pyrazolines and Pyrazolidines by [3+2] Cycloadditions of Azomethine Imines
by Franc Požgan, Hamad Al Mamari, Uroš Grošelj, Jurij Svete and Bogdan Štefane
Molecules 2018, 23(1), 3; https://doi.org/10.3390/molecules23010003 - 21 Dec 2017
Cited by 30 | Viewed by 7607
Abstract
Asymmetric [3+2] cycloadditions of azomethine imines comprise a useful synthetic tool for the construction of pyrazole derivatives with a variable degree of saturation and up to three stereogenic centers. As analogues of pyrrolidines and imidazolidines that are abundant among natural products, pyrazoline and [...] Read more.
Asymmetric [3+2] cycloadditions of azomethine imines comprise a useful synthetic tool for the construction of pyrazole derivatives with a variable degree of saturation and up to three stereogenic centers. As analogues of pyrrolidines and imidazolidines that are abundant among natural products, pyrazoline and pyrazolidine derivatives represent attractive synthetic targets due to their extensive applications in the chemical and medicinal industries. Following the increased understanding of the mechanistic aspect of metal-catalyzed and organocatalyzed [3+2] cycloadditions of 1,3-dipoles gained over recent years, significant strides have been taken to design and develop new protocols that proceed efficiently under mild synthetic conditions and duly benefit from superior functional group tolerance and selectivity. In this review, we represent the current state of the art in this field and detailed methods for the synthesis of non-racemic pyrazolines and pyrazolidines via [3+2] metal and organocatalyzed transformations reported since the seminal work of Kobayashi et al. and Fu et al. in 2002 and 2003 up to the end of year 2017. Full article
(This article belongs to the Special Issue Pyrazole Derivatives)
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17 pages, 922 KiB  
Review
Enantioselective Organocatalyzed Synthesis of 2-Amino-3-cyano-4H-chromene Derivatives
by Isaac G. Sonsona, Eugenia Marqués-López and Raquel P. Herrera
Symmetry 2015, 7(3), 1519-1535; https://doi.org/10.3390/sym7031519 - 26 Aug 2015
Cited by 36 | Viewed by 9769
Abstract
The structural motif that results from the fusion of a benzene ring to a heterocyclic pyran ring, known as chromene, is broadly found in nature and it has been reported to be associated with a wide range of biological activity. Moreover, asymmetric organocatalysis [...] Read more.
The structural motif that results from the fusion of a benzene ring to a heterocyclic pyran ring, known as chromene, is broadly found in nature and it has been reported to be associated with a wide range of biological activity. Moreover, asymmetric organocatalysis is a discipline in expansion that is already recognized as a well-established tool for obtaining enantiomerically enriched compounds. This review covers the particular case of the asymmetric synthesis of 2-amino-3-cyano-4H-chromenes using organocatalysis. Herein, we show the most illustrative examples of the methods developed by diverse research groups, following a classification based on these five different approaches: (1) addition of naphthol compounds to substituted α,α-dicyanoolefins; (2) addition of malononitrile to substituted o-vinylphenols; (3) addition of malononitrile to N-protected o-iminophenols; (4) Michael addition of nucleophiles to 2-iminochromene derivatives; and (5) organocatalyzed formal [4+2] cycloaddition reaction. In most cases, chiral thioureas have been found to be effective catalysts to promote the synthetic processes, and generally a bifunctional mode of action has been envisioned for them. In addition, squaramides and cinchona derivatives have been occasionally used as suitable catalysts for the substrates activation. Full article
(This article belongs to the Special Issue Asymmetric Catalysis)
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