Bismuth triflate (0.1 mol %) is a highly efficient catalyst for the cyclization of citronellal 1, a reaction that yields a ratio of 80:20 of isopulegol 2 and neoisopulegol 3. This methodology has also been extended to the synthesis of substituted piperidines. The bismuth triflate catalyzed ene reaction of aldehyde 4 gives a 70:30 mixture of piperidines 5 and 6. The advantages of these methods include the use of a highly efficient catalyst that is relatively nontoxic, cheap and easy to handle.
Bibliographical noteFunding Information:
We are grateful to the National Science Foundation for an RUI (Research at An Undergraduate Institution) grant. We also wish to acknowledge Research Corporation for a Cottrell College Science Award. R.M. wishes to thank The Camille and Henry Dreyfus Foundation for a Henry Dreyfus Teacher Scholar Award.
- Bismuth and compounds
- Carbonyl-ene reaction
- Lewis acids