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

Department of Chemistry

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

24 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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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; Chan, Yu Te; Tsai, Ming-Kang ; Chen, Kwunmin.

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, 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, vol. 18, no. 13, pp. 3098-3101. https://doi.org/10.1021/acs.orglett.6b01265

Gurubrahamam R, Gao BF, Chen YM, Chan YT, Tsai M-K , Chen K. 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. 2016 Jul 1;18(13):3098-3101. https://doi.org/10.1021/acs.orglett.6b01265

Gurubrahamam, Ramani ; Gao, Bing Fong ; Chen, Yan Ming ; Chan, Yu Te ; Tsai, Ming-Kang ; Chen, Kwunmin. / 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. In: Organic Letters. 2016 ; Vol. 18, No. 13. pp. 3098-3101.

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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.",

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AU - Gurubrahamam, Ramani

AU - Gao, Bing Fong

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AU - Chan, Yu Te

AU - Tsai, Ming-Kang

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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

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