Organocascade Synthesis of Annulated (Z)-2-Methylenepyrans: Nucleophilic Conjugate Addition of Hydroxycoumarins and Pyranone to Branched Nitro Enynes via Allene Formation/Oxa-Michael Cyclization/Alkene Isomerization Sequence

Ramani Gurubrahamam; Bing Fong Gao; Yan Ming Chen; Yu Te Chan; Ming Kang Tsai; Kwunmin Chen

doi:10.1021/acs.orglett.6b01265

Organocascade Synthesis of Annulated (Z)-2-Methylenepyrans: Nucleophilic Conjugate Addition of Hydroxycoumarins and Pyranone to Branched Nitro Enynes via Allene Formation/Oxa-Michael Cyclization/Alkene Isomerization Sequence

Ramani Gurubrahamam, Bing Fong Gao, Yan Ming Chen, Yu Te Chan, Ming Kang Tsai^*, Kwunmin Chen

^*Corresponding author for this work

Department of Chemistry

Research output: Contribution to journal › Article › peer-review

41 Citations (Scopus)

Abstract

An efficient organocatalytic reaction using 1,3-nitro enynes with 4-hydroxycoumarin and 4-hydroxy-6-methyl-2-pyrone to afford pyrano-annulated scaffolds in high yield (up to 88% yield) and excellent stereoselectivities (up to >20:1 dr and >99% ee) is described. The reaction proceeded through sequential conjugate addition, allene formation, intramolecular oxa-Michael 6-endo-dig cyclization and DABCO-catalyzed olefin isomerization. A kinetic profile for isomerization was established. The mechanism for the organocascade reaction was proposed according to requisite computational and mechanistic experimental studies.

Original language	English
Pages (from-to)	3098-3101
Number of pages	4
Journal	Organic Letters
Volume	18
Issue number	13
DOIs	https://doi.org/10.1021/acs.orglett.6b01265
Publication status	Published - 2016 Jul 1

ASJC Scopus subject areas

Biochemistry
Physical and Theoretical Chemistry
Organic Chemistry

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CCDC 1465297: Experimental Crystal Structure Determination
Gurubrahamam, R. (Creator), Gao, B. (Creator), Chen, Y. M. (Creator), Chan, Y. (Creator), Tsai, M. B. (Creator) & Chen, K. (Creator), Unknown Publisher, 2016
DOI: 10.5517/ccdc.csd.cc1l5rn5, http://www.ccdc.cam.ac.uk/services/structure_request?id=doi:10.5517/ccdc.csd.cc1l5rn5&sid=DataCite
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Gurubrahamam, R., Gao, B. F., Chen, Y. M., Chan, Y. T., Tsai, M. K., & Chen, K. (2016). Organocascade Synthesis of Annulated (Z)-2-Methylenepyrans: Nucleophilic Conjugate Addition of Hydroxycoumarins and Pyranone to Branched Nitro Enynes via Allene Formation/Oxa-Michael Cyclization/Alkene Isomerization Sequence. Organic Letters, 18(13), 3098-3101. https://doi.org/10.1021/acs.orglett.6b01265

Organocascade Synthesis of Annulated (Z)-2-Methylenepyrans: Nucleophilic Conjugate Addition of Hydroxycoumarins and Pyranone to Branched Nitro Enynes via Allene Formation/Oxa-Michael Cyclization/Alkene Isomerization Sequence. / Gurubrahamam, Ramani; Gao, Bing Fong; Chen, Yan Ming et al.
In: Organic Letters, Vol. 18, No. 13, 01.07.2016, p. 3098-3101.

Research output: Contribution to journal › Article › peer-review

Gurubrahamam, R, Gao, BF, Chen, YM, Chan, YT, Tsai, MK & Chen, K 2016, 'Organocascade Synthesis of Annulated (Z)-2-Methylenepyrans: Nucleophilic Conjugate Addition of Hydroxycoumarins and Pyranone to Branched Nitro Enynes via Allene Formation/Oxa-Michael Cyclization/Alkene Isomerization Sequence', Organic Letters, vol. 18, no. 13, pp. 3098-3101. https://doi.org/10.1021/acs.orglett.6b01265

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title = "Organocascade Synthesis of Annulated (Z)-2-Methylenepyrans: Nucleophilic Conjugate Addition of Hydroxycoumarins and Pyranone to Branched Nitro Enynes via Allene Formation/Oxa-Michael Cyclization/Alkene Isomerization Sequence",

abstract = "An efficient organocatalytic reaction using 1,3-nitro enynes with 4-hydroxycoumarin and 4-hydroxy-6-methyl-2-pyrone to afford pyrano-annulated scaffolds in high yield (up to 88% yield) and excellent stereoselectivities (up to >20:1 dr and >99% ee) is described. The reaction proceeded through sequential conjugate addition, allene formation, intramolecular oxa-Michael 6-endo-dig cyclization and DABCO-catalyzed olefin isomerization. A kinetic profile for isomerization was established. The mechanism for the organocascade reaction was proposed according to requisite computational and mechanistic experimental studies.",

author = "Ramani Gurubrahamam and Gao, {Bing Fong} and Chen, {Yan Ming} and Chan, {Yu Te} and Tsai, {Ming Kang} and Kwunmin Chen",

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AU - Gurubrahamam, Ramani

AU - Gao, Bing Fong

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AU - Chan, Yu Te

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AB - An efficient organocatalytic reaction using 1,3-nitro enynes with 4-hydroxycoumarin and 4-hydroxy-6-methyl-2-pyrone to afford pyrano-annulated scaffolds in high yield (up to 88% yield) and excellent stereoselectivities (up to >20:1 dr and >99% ee) is described. The reaction proceeded through sequential conjugate addition, allene formation, intramolecular oxa-Michael 6-endo-dig cyclization and DABCO-catalyzed olefin isomerization. A kinetic profile for isomerization was established. The mechanism for the organocascade reaction was proposed according to requisite computational and mechanistic experimental studies.

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Organocascade Synthesis of Annulated (Z)-2-Methylenepyrans: Nucleophilic Conjugate Addition of Hydroxycoumarins and Pyranone to Branched Nitro Enynes via Allene Formation/Oxa-Michael Cyclization/Alkene Isomerization Sequence

Abstract

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CCDC 1465297: Experimental Crystal Structure Determination

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