Abstract
Transient dative substrate-Ti interactions have been found to play a key role in controlling the regioselectivity of alkyne insertion and [2+2] cycloaddition in Ti-catalyzed [2+2+1] pyrrole synthesis and Ti-catalyzed alkyne hydroamination. TMS-protected alkynes with pendent Lewis basic groups can invert the regioselectivity of TMS-protected alkyne insertion, leading to the selective formation of highly substituted 3-TMS pyrroles. The competency of various potential directing groups was investigated, and it was found that the directing-group effect can be tuned by modifying the catalyst Lewis acidity, the directing-group basicity, or the directing-group tether length. Dative directing-group effects are unexplored with Ti catalysts, and this study demonstrates the potential power of dative substrate-Ti interactions in tuning selectivity.
| Original language | English (US) |
|---|---|
| Pages (from-to) | 216-223 |
| Number of pages | 8 |
| Journal | ACS Catalysis |
| Volume | 9 |
| Issue number | 1 |
| DOIs | |
| State | Published - Jan 4 2019 |
Bibliographical note
Funding Information:Financial support was provided by the National Institutes of Health (1R35GM119457) and the Alfred P. Sloan Foundation (I.A.T. is a 2017 Sloan Fellow). Equipment for the Chemistry Department NMR facility was supported through a grant from the National Institutes of Health (S10OD011952) with matching funds from the University of Minnesota.
Publisher Copyright:
Copyright © 2018 American Chemical Society.
Keywords
- alkynes
- directing-group effects
- multicomponent reactions
- pyrroles
- titanium