Hydroaminoalkylation: Tantalum Catalysts for C-H Alkylation of Amines
stoichiometry 1:1 + low temperature + short reaction times + high selectivity
- Compatible with unactivated alkenes
- Ratio of alkene : secondary amine = 1:1
- 100% atom-economic reaction
- At 110°C conversion of terminal alkenes
- At 130°C conversion of internal alkenes
- Reaction time 1h (terminal), 20h (internal)
The catalytic functionalization of alkenes represents an efficient method for the synthesis of amine building blocks for the chemical, pharmaceutical, and agrochemical industry. Current catalytic amine functionalization methods are typically not compatible with unactivated amines. Often, a stoichiometric excess of alkene (>1.5 eq.), high reaction temperatures (>130°C), and long reaction times (>20h) are required in addition to co-catalysts, protecting/directing groups on the amines, and various reaction additives, adding to the operational costs and making these processes not environmentally sustainable.
Researchers at The University of British Columbia have developed a suite of tantalum (V) catalysts. The tested catalysts require only stoichiometric amounts of alkene and secondary amine (ratio 1:1), wherein neat reactions are favorable. Reactions proceed with excellent region-selectivity at modest temperatures with fast reaction times. For example, the hydroamination of N-methylaniline with 1-octene yields up to 93% of the branched product in 1 hour (TOF 18.6h-1). No reaction by-products are generated, as this is a 100% atom-economic reaction.