Stoichiometric and catalytic inter- and intramolecular hydroamination of terminal alkynes by frustrated Lewis pairs

Tayseer Mahdi; Douglas W Stephan

doi:10.1002/chem.201501535

Stoichiometric and catalytic inter- and intramolecular hydroamination of terminal alkynes by frustrated Lewis pairs

Chemistry. 2015 Jul 27;21(31):11134-42. doi: 10.1002/chem.201501535. Epub 2015 Jun 25.

Authors

Tayseer Mahdi¹, Douglas W Stephan²

Affiliations

¹ Department of Chemistry, University of Toronto, 80 St. George St, Toronto, ON, M5S 2H6 (Canada).
² Department of Chemistry, University of Toronto, 80 St. George St, Toronto, ON, M5S 2H6 (Canada). dstephan@chem.utoronto.ca.

PMID: 26110237
DOI: 10.1002/chem.201501535

Abstract

Frustrated Lewis pairs (FLPs) based on sterically encumbered anilines and the Lewis acid B(C6 F5 )3 were found to react with terminal alkynes effecting intermolecular hydroamination affording iminium alkynylborate species of the form [RPhNC(R')Me][R'CCB(C6 F5 )3 ]. In these cases, the reagent ratio of borane, aniline, and alkyne is 1:1:2. These reactions could also be performed in an intramolecular fashion by using anilines with alkynyl substituents effecting cyclization reactions. The use of 10 mol % B(C6 F5 )3 under a H2 atmosphere provides a one-pot synthesis of the pyrrolidine 12, the piperidines 13-15, the azepane 16, the isoindoline 17, and the benzoxazine 18.

Keywords: alkynes; anilines; frustrated Lewis pairs; hydroamination; hydrogen activation.