Electrostatically enhanced phosphoric acids and their applications in asymmetric friedel-crafts alkylations

Jie Ma; Steven R. Kass

doi:10.1021/acs.joc.9b01741

Electrostatically enhanced phosphoric acids and their applications in asymmetric friedel-crafts alkylations

Jie Ma, Steven R. Kass

Chemistry (Twin Cities)

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

11 Scopus citations

Abstract

A series of electrostatically enhanced phosphoric acid catalysts were synthesized and studied. These compounds possess two positively charged N-octylpyridinium or triarylphosphonium ion centers at the 3,3′-positions of the (R)-BINOL backbone to enhance reactivity and provide needed steric bulk for enantioselective transformations. Catalytic activities for Friedel-Crafts alkylations of indoles with trans-β-nitrostyrenes were studied. Both types of catalysts accelerate reaction conversions relative to noncharged analogues, and good enantioselectivities up to 90% ee are observed with the phosphonium-ion-tagged phosphoric acids. This transformation also can be scaled up to synthetically useful amounts, affording >250 mg of product without losing any reactivity or selectivity.

Original language	English (US)
Pages (from-to)	11125-11134
Number of pages	10
Journal	Journal of Organic Chemistry
Volume	84
Issue number	17
DOIs	https://doi.org/10.1021/acs.joc.9b01741
State	Published - Sep 6 2019

Bibliographical note

Funding Information:
Generous support from the National Science Foundation (CHE-1665392) and the Petroleum Research Fund (55631-ND4) as administered by the American Chemical Society is gratefully acknowledged.

Publisher Copyright:
© 2019 American Chemical Society.

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10.1021/acs.joc.9b01741

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title = "Electrostatically enhanced phosphoric acids and their applications in asymmetric friedel-crafts alkylations",

abstract = "A series of electrostatically enhanced phosphoric acid catalysts were synthesized and studied. These compounds possess two positively charged N-octylpyridinium or triarylphosphonium ion centers at the 3,3′-positions of the (R)-BINOL backbone to enhance reactivity and provide needed steric bulk for enantioselective transformations. Catalytic activities for Friedel-Crafts alkylations of indoles with trans-β-nitrostyrenes were studied. Both types of catalysts accelerate reaction conversions relative to noncharged analogues, and good enantioselectivities up to 90% ee are observed with the phosphonium-ion-tagged phosphoric acids. This transformation also can be scaled up to synthetically useful amounts, affording >250 mg of product without losing any reactivity or selectivity.",

author = "Jie Ma and Kass, {Steven R.}",

note = "Funding Information: Generous support from the National Science Foundation (CHE-1665392) and the Petroleum Research Fund (55631-ND4) as administered by the American Chemical Society is gratefully acknowledged. Publisher Copyright: {\textcopyright} 2019 American Chemical Society.",

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AU - Kass, Steven R.

N1 - Funding Information: Generous support from the National Science Foundation (CHE-1665392) and the Petroleum Research Fund (55631-ND4) as administered by the American Chemical Society is gratefully acknowledged. Publisher Copyright: © 2019 American Chemical Society.

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N2 - A series of electrostatically enhanced phosphoric acid catalysts were synthesized and studied. These compounds possess two positively charged N-octylpyridinium or triarylphosphonium ion centers at the 3,3′-positions of the (R)-BINOL backbone to enhance reactivity and provide needed steric bulk for enantioselective transformations. Catalytic activities for Friedel-Crafts alkylations of indoles with trans-β-nitrostyrenes were studied. Both types of catalysts accelerate reaction conversions relative to noncharged analogues, and good enantioselectivities up to 90% ee are observed with the phosphonium-ion-tagged phosphoric acids. This transformation also can be scaled up to synthetically useful amounts, affording >250 mg of product without losing any reactivity or selectivity.

AB - A series of electrostatically enhanced phosphoric acid catalysts were synthesized and studied. These compounds possess two positively charged N-octylpyridinium or triarylphosphonium ion centers at the 3,3′-positions of the (R)-BINOL backbone to enhance reactivity and provide needed steric bulk for enantioselective transformations. Catalytic activities for Friedel-Crafts alkylations of indoles with trans-β-nitrostyrenes were studied. Both types of catalysts accelerate reaction conversions relative to noncharged analogues, and good enantioselectivities up to 90% ee are observed with the phosphonium-ion-tagged phosphoric acids. This transformation also can be scaled up to synthetically useful amounts, affording >250 mg of product without losing any reactivity or selectivity.

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Electrostatically enhanced phosphoric acids and their applications in asymmetric friedel-crafts alkylations

Abstract

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