Synthesis of 3,4-disubstituted piperidines by ene cyclisation of 4-aza-1,7-dienes
摘要:
Ene cyclisation of a variety of 4-aza-1,7-dienes affords 3,4-disubstituted piperidines. In particular, cyclisation of diesters 14 and 20 catalysed by MeAlCl2 gives the corresponding trans 3,4-disubstituted piperidines with diastereomeric ratios of > 200:1. (c) 2005 Elsevier Ltd. All rights reserved.
A highly diastereo- and enantioselective intramolecular Alder-ene reaction with an alkene as the enophile has been developed by using a chiral N,N′-dioxide/nickel(II) complex as the catalyst. This protocol provides a facileroute towards the synthesis of diverse 3,4-disubstituted chroman, tetrahydroquinoline, piperidine and thiochroman derivatives in high yields with good to excellent diastereo- and