Seminar


Department of Chemistry
Indian Institute of Technology Delhi

Phosphoric Acid-Catalyzed, Enantioselective Transformations of H-Bonded ortho-Quinone Methides and ortho-Quinone Methide Imines

Dr. Christoph Schneider
University of Leipzig, Institute of Organic Chemistry, Johannisallee 29, D-04103 Leipzig, Germany. schneider@chemie.uni-leipzig.de

Date: August 27th 2018 (Monday)
Time: 4 PM
Venue: Committee Room, Chemistry Department, 6th Floor

Ortho-quinone methides are highly reactive synthetic intermediates which have only recently begun to attract the attention of synthetic organic chemists.1 They typically react as polarized, electronpoor 1-oxabutadienes with electronrich [2π]-components in hetero-Diels-Alder reactions or with nucleophiles in a conjugate addition both with reconstitution of the aromatic π-system. Using chiral phosphoric acid catalysis (HX*) we have been able to generate hydrogen-bonded ortho-quinone methides 1 in situ starting from readily accessible benzhydryl alcohols. A variety of electronrich π-nucleophiles were then added in a conjugate addition event with excellent enantioselectivity. β-Dicarbonyl compounds, enamides, indoles, and naphthols are among the most suitable nucleophiles employed for this purpose and deliver a broad range of benzo-annulated oxygen heterocycles.2 Furthermore, in a cooperative rhodium-/phosphoric acid-catalyzed approach ortho-quinone methides are trapped with oxonium ylides also generated in situ to yield highly substituted and densely functionalized chromanes.3 The extension of this strategy to ortho-quinone methide imines 2 and the synthesis of nitrogen heterocycles proceeds likewise with good enantio- and diastereocontrol.4,5


    References:
  1. Reviews: a) W.-J. Bai, J. G. David, Z.-G. Feng, M. G. Weaver, K.-L. Wu, T. R. R. Pettus, Acc. Chem. Res. 2014, 47, 3655; b) L. Caruana, M. Fochi, L. Bernardi, Molecules 2015, 20, 11733; c) Z. Wang, J. Sun, Synthesis 2015, 47, 3629; d) A. A. Jaworski, K. A. Scheidt, J. Org. Chem. 2016, 81, 10145-10153.
  2. a) O. El-Sepelgy, S. Haseloff, S. K. Alamsetti, C. Schneider, Angew. Chem. Int. Ed. 2014, 53, 7923; b) S. Saha, C. Schneider, Chem. – Eur. J. 2015, 21, 2348; c) S. Saha, C. Schneider, Org. Lett. 2015, 17, 648; d) S. Saha, S. K. Alamsetti, C. Schneider, Chem. Commun. 2015, 51, 1461.
  3. S. K. Alamsetti, M. Spanka, C. Schneider, Angew. Chem. Int. Ed. 2016, 55, 2392.
  4. a) M. Kretzschmar, T. Hodik, C. Schneider, Angew. Chem. Int. Ed. 2016, 55, 9788, b) T. Hodik, C. Schneider, Org. Biomol. Chem. 2017, 15, 3706-3716.
  5. M. Kretzschmar, F. Hofmann, D. Moock, C. Schneider, Angew. Chem. Int. Ed. 2018, 57, 4774.


All are cordially invited to attend.
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