Regioselective Amine-Borane Cyclization: Towards the Synthesis of 1,2-BN-3-Cyclohexene by Copper-Assisted Triazole/Gold Catalysis

Stephen E Motika; Qiaoyi Wang; Novruz G Akhmedov; Lukasz Wojtas; Xiaodong Shi

doi:10.1002/anie.201604986

Regioselective Amine-Borane Cyclization: Towards the Synthesis of 1,2-BN-3-Cyclohexene by Copper-Assisted Triazole/Gold Catalysis

Angew Chem Int Ed Engl. 2016 Sep 12;55(38):11582-6. doi: 10.1002/anie.201604986. Epub 2016 Aug 17.

Authors

Stephen E Motika¹, Qiaoyi Wang², Novruz G Akhmedov², Lukasz Wojtas¹, Xiaodong Shi³

Affiliations

¹ Department of Chemistry, University of South Florida, Tampa, FL, 33620, USA.
² Department of Chemistry, West Virginia University, Morgantown, WV, 26505, USA.
³ Department of Chemistry, University of South Florida, Tampa, FL, 33620, USA. xmshi@usf.edu.

PMID: 27532900
DOI: 10.1002/anie.201604986

Abstract

The combination of triazole/gold (TA-Au) and Cu(OTf)2 is identified as the optimal catalytic system for promoting intramolecular hydroboration for the synthesis of a six-membered cyclic amine-borane. Excellent yields (up to 95 %) and regioselectivities (5-exo vs. 6-endo) were achieved through catalyst control and sequential dilution. Good functional-group tolerance was attained, thus allowing the preparation of highly functionalized cyclic amine-borane substrates, which could not be achieved using other methods. Deuterium-labeling studies support the involvement of a hydride addition to a gold-activated alkyne with subsequent C-B bond formation.

Keywords: boranes; copper; gold; heterocycles; reaction mechanisms.

Publication types

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