Frustrated Lewis Pair-Catalyzed Cycloisomerization of 1,5-Enynes via a 5-endo-dig Cyclization/Protodeborylation Sequence

Sergej Tamke; Zheng-Wang Qu; Nikolai A Sitte; Ulrich Flörke; Stefan Grimme; Jan Paradies

doi:10.1002/anie.201511921

Frustrated Lewis Pair-Catalyzed Cycloisomerization of 1,5-Enynes via a 5-endo-dig Cyclization/Protodeborylation Sequence

Angew Chem Int Ed Engl. 2016 Mar 18;55(13):4336-9. doi: 10.1002/anie.201511921. Epub 2016 Mar 3.

Authors

Sergej Tamke¹, Zheng-Wang Qu², Nikolai A Sitte¹, Ulrich Flörke³, Stefan Grimme⁴, Jan Paradies⁵

Affiliations

¹ Institute of Organic Chemistry, University of Paderborn, Warburger Strasse 100, 33098, Paderborn, Germany.
² Mulliken Center for Theoretical Chemistry, Institut für Physikalische und Theoretische Chemie, University of Bonn, Beringstrasse 4, 53115, Bonn, Germany.
³ Institute of Inorganic and Analytical Chemistry, University of Paderborn, Germany.
⁴ Mulliken Center for Theoretical Chemistry, Institut für Physikalische und Theoretische Chemie, University of Bonn, Beringstrasse 4, 53115, Bonn, Germany. grimme@thch.uni-bonn.de.
⁵ Institute of Organic Chemistry, University of Paderborn, Warburger Strasse 100, 33098, Paderborn, Germany. jan.paradies@uni-paderborn.de.

PMID: 26939012
DOI: 10.1002/anie.201511921

Abstract

The first frustrated Lewis pair-catalyzed cycloisomerization of a series of 1,5-enynes was developed. The reaction proceeds via the π-activation of the alkyne and subsequent 5-endo-dig cyclization with the adjacent alkene. The presence of PPh3 was of utmost importance on the one hand to prevent side reactions (for example, 1,1-carboboration) and on the other hand for the efficient protodeborylation to achieve the catalytic turnover. The mechanism is explained on the basis of quantum-chemical calculations, which are in full agreement with the experimental observations.

Keywords: 1,5-enynes; cycloisomerization; frustrated Lewis pairs; kinetic isotope effect; protodeborylation.

Publication types

Research Support, Non-U.S. Gov't