Synthesis of 7-Prenylindole

I have seen some days ago this publication from M. Pirrung concerning the synthesis of 7-Prenylindole starting from indoline. This molecule is key ring in many natural products. As depicted below, the synthesis starts with copper catalyzed N-alkylation of indoline with 2-chloro- 2-methylbut-3-yne in THF in 91% yield on 10 mmol scale. After the reduction of the CC triple bound in alkene, the dimethylallylindoline obtained is submitted to a micro-wave assisted aza-claisen rearrangement in 90% yield (this step has been performed in a monomode micro-wave oven in a sealed tube at 150°C). Finally, the indoline has been oxidized into indole with MnO2 in DCM in 88% Yield.



I like this synthesis first, of course because this is indole ring, but also because the author uses one of my favorite reaction, the aza-claisen rearrangement, and my favorite tool for organic synthesis, a micro-wave oven.

Practical Synthesis of 7-Prenylindole
Xin Xiong and Michael C. Pirrung
http://pubs3.acs.org/acs/journals/doilookup?in_doi=10.1021/jo070734v

For the application of the 7-Prenylindole from the same author see:

Glyceraldehyde 3-Phosphate Dehydrogenase Is a Cellular Target of the Insulin Mimic Demethylasterriquinone B1
Hyunsoo Kim, Liu Deng, Xin Xiong, William D. Hunter, Melissa C. Long, and Michael C. Pirrung
http://pubs3.acs.org/acs/journals/doilookup?in_doi=10.1021/jm070437i