RSS-Feed abonnieren
DOI: 10.1055/s-2008-1072762
Hydroamination of Nonactivated Alkenes
Rezensent(en):Benjamin List, Frank LayGeorg-August-Universität Göttingen, Germany
Phosphoric Acid Diesters as Efficient Catalysts for Hydroaminations of Nonactivated Alkenes and an Application to Asymmetric Hydroaminations
Synlett 2008, 995-998
Publikationsverlauf
Publikationsdatum:
21. Mai 2008 (online)
Key words
hydroamination - phosphoric acid - alkenes - cycloisomerization
Significance
A catalytic amount of Brønsted acid enables high yielding intramolecular hydroaminations of electronically unactivated alkenes with basic amines. Screenings identified phosphoric acid 1 as the most active catalyst for this cycloisomerization. Substrates with ether, nitro, ester, or chloro functionalities are tolerated. By using enantiomerically pure phosphoric acid (R)-1a the authors show an unprecedented example of a metal-free asymmetric hydroamination of nonactivated alkenes, albeit with modest selectivity (er = 58.5:41.5).
Comment
This intramolecular addition of an amine to a C-C double bond depicts a direct and atom-economical access to N-heterocycles, which are ubiquitous in natural products as well as biologically active compounds. Most organocatalytic additions of N-nucleophiles to olefins require activation of the alkene functionality. The observed effectiveness of this addition might be due to the intramolecular nature of this cycloisomerization. A screening of different enantiopure phosphoric acids might result in higher enantiomeric ratios.