Stoichiometric Reactions of Enamines Derived from Diphenylprolinol Silyl Ethers with Nitro Olefins and Lessons for the Corresponding Organocatalytic Conversions – a Survey

Authors

  • Dieter Seebach,

    Corresponding author
    1. Laboratorium für Organische Chemie, Departement Chemie und Angewandte Biowissenschaften, ETH-Zürich, Hönggerberg HCI, Wolfgang-Pauli-Strasse 10, CH-8093 Zürich, (phone: +41-44-632-2990; fax: +41-44-632-1144)
    • Laboratorium für Organische Chemie, Departement Chemie und Angewandte Biowissenschaften, ETH-Zürich, Hönggerberg HCI, Wolfgang-Pauli-Strasse 10, CH-8093 Zürich, (phone: +41-44-632-2990; fax: +41-44-632-1144)
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  • Xiaoyu Sun,

    1. Laboratorium für Organische Chemie, Departement Chemie und Angewandte Biowissenschaften, ETH-Zürich, Hönggerberg HCI, Wolfgang-Pauli-Strasse 10, CH-8093 Zürich, (phone: +41-44-632-2990; fax: +41-44-632-1144)
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    • Postdoctoral fellow at ETH Zürich 2011/12, partially financed by Swiss National Science Foundation (SNF-No. 200020-126693). All the isolations of intermediates and preparations of single crystals, described herein, have been carried out by X. S.

  • Marc-Olivier Ebert,

    1. Laboratorium für Organische Chemie, Departement Chemie und Angewandte Biowissenschaften, ETH-Zürich, Hönggerberg HCI, Wolfgang-Pauli-Strasse 10, CH-8093 Zürich, (phone: +41-44-632-2990; fax: +41-44-632-1144)
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  • W. Bernd Schweizer,

    1. Laboratorium für Organische Chemie, Departement Chemie und Angewandte Biowissenschaften, ETH-Zürich, Hönggerberg HCI, Wolfgang-Pauli-Strasse 10, CH-8093 Zürich, (phone: +41-44-632-2990; fax: +41-44-632-1144)
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  • Nirupam Purkayastha,

    1. Laboratorium für Organische Chemie, Departement Chemie und Angewandte Biowissenschaften, ETH-Zürich, Hönggerberg HCI, Wolfgang-Pauli-Strasse 10, CH-8093 Zürich, (phone: +41-44-632-2990; fax: +41-44-632-1144)
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    • Postdoctoral fellow at ETH Zürich 2012/13.

  • Albert K. Beck,

    1. Laboratorium für Organische Chemie, Departement Chemie und Angewandte Biowissenschaften, ETH-Zürich, Hönggerberg HCI, Wolfgang-Pauli-Strasse 10, CH-8093 Zürich, (phone: +41-44-632-2990; fax: +41-44-632-1144)
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  • Jörg Duschmalé,

    1. Laboratorium für Organische Chemie, Departement Chemie und Angewandte Biowissenschaften, ETH-Zürich, Hönggerberg HCI, Wolfgang-Pauli-Strasse 10, CH-8093 Zürich, (phone: +41-44-632-2990; fax: +41-44-632-1144)
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  • Helma Wennemers,

    1. Laboratorium für Organische Chemie, Departement Chemie und Angewandte Biowissenschaften, ETH-Zürich, Hönggerberg HCI, Wolfgang-Pauli-Strasse 10, CH-8093 Zürich, (phone: +41-44-632-2990; fax: +41-44-632-1144)
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  • Takasuke Mukaiyama,

    1. Tokyo University of Science, Department of Industrial Chemistry, Faculty of Engineering, Kagurazaka, Shinjuku-ku, Tokyo 162-8601, Japan and Department of Chemistry, Tohoku University, 6-3 Aramaki-Aza, Aoba-ku, Sendai, Miyagi 980-8578, Japan (phone: +81-22-795-3554; fax: +81-22-795-6566)
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    • Some of the experiments were carried out by T. M. during a three-month stay at ETH Zürich (August–October 2012), financed by Tokyo University of Science.

  • Meryem Benohoud,

    1. Tokyo University of Science, Department of Industrial Chemistry, Faculty of Engineering, Kagurazaka, Shinjuku-ku, Tokyo 162-8601, Japan and Department of Chemistry, Tohoku University, 6-3 Aramaki-Aza, Aoba-ku, Sendai, Miyagi 980-8578, Japan (phone: +81-22-795-3554; fax: +81-22-795-6566)
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    • Postdoctoral fellow at Tokyo University of Science (2010–2012), financed by JSPS (PE10034; P10817).

  • Yujiro Hayashi,

    Corresponding author
    1. Tokyo University of Science, Department of Industrial Chemistry, Faculty of Engineering, Kagurazaka, Shinjuku-ku, Tokyo 162-8601, Japan and Department of Chemistry, Tohoku University, 6-3 Aramaki-Aza, Aoba-ku, Sendai, Miyagi 980-8578, Japan (phone: +81-22-795-3554; fax: +81-22-795-6566)
    • Tokyo University of Science, Department of Industrial Chemistry, Faculty of Engineering, Kagurazaka, Shinjuku-ku, Tokyo 162-8601, Japan and Department of Chemistry, Tohoku University, 6-3 Aramaki-Aza, Aoba-ku, Sendai, Miyagi 980-8578, Japan (phone: +81-22-795-3554; fax: +81-22-795-6566)
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  • Markus Reiher

    Corresponding author
    1. Laboratorium für Physikalische Chemie, Departement Chemie und Angewandte Biowissenschaften, ETH-Zürich, Hönggerberg HCI F 235, Wolfgang-Pauli-Strasse 10, CH-8093 Zürich, (phone: +41-44-633-4308; fax: +41-44-633-1595)
    • Laboratorium für Physikalische Chemie, Departement Chemie und Angewandte Biowissenschaften, ETH-Zürich, Hönggerberg HCI F 235, Wolfgang-Pauli-Strasse 10, CH-8093 Zürich, (phone: +41-44-633-4308; fax: +41-44-633-1595)
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  • Part of the results described herein had been reported in a preliminary communication [1].

Abstract

The stoichiometric reactions of enamines prepared from aldehydes and diphenyl-prolinol silyl ethers (intermediates of numerous organocatalytic processes) with nitro olefins have been investigated. As reported in the last century for simple achiral and chiral enamines, the products are cyclobutanes (4 with monosubstituted nitro-ethenes), dihydro-oxazine N-oxide derivatives (5 with disubstituted nitro-ethenes), and nitro enamines derived from γ-nitro aldehydes (6, often formed after longer reaction times). The same types of products were shown to be formed, when the reactions were carried out with peptides H-Pro-Pro-Xaa-OMe that lack an acidic H-atom. Functionalized components such as alkoxy enamines, nitro-acrylates, acetamido-nitro-ethylene, or hydroxylated nitro olefins also form products carrying the diphenyl-prolinol silyl ether as a substituent. All of these products must be considered intermediates in the corresponding catalytic reactions; the investigation of their chemical properties provided useful hints about the rates, the conditions, the catalyst resting states or irreversible traps, and/or the limitations of the corresponding organocatalytic processes. High-level DFT and MP2 computations of the structures of alkoxy enamines and thermodynamic data of a cyclobutane dissociation are also described. Some results obtained with the stoichiometrically prepared intermediates are not compatible with previous mechanistic proposals and assumptions.

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