The Synaptic Leap

A new patent application using a multistep reaction (Ugi reaction) for the synthesis of Praziquantel
 

 
This recent patent application describes a new method for the synthesis of rac-Praziquantel.[1] The key step in this procedure is a multi-step reaction, also known as the Ugi reaction, which enables the formation of the intermediate 5 up to 89%. [2,3] Under Broensted-acidic conditions a Pictet-Spegler-cyclization yields 6 or Praziquantel 7, depending on the various substituents R2.

[1]    “Novel Synthesis of Praziquantel“, A. Dömling, Patent Application 2009, WO 2009/11533(A1), Language: German.
[2]    “Multicomponent Reactions with Isocyanides” A. Dömling, I. Ugi, Angew. Chem.2000, 39, 18, 3168 – 3210.
[3]    "Recent Developments in Isocyanide Based Multicomponent Reactions in Applied Chemistry", A. Dömling, Chem. Rev. 2006, 106 ,1, 17–89; DOI: 10.1021/cr0505728.
 
We just tried this exact reaction 2 weeks ago :) http://usefulchem.wikispaces.com/Exp258 [JCB]