Didehydro-4-piperidinones

Didehydro-4-piperidinones of type 2-456 and 2-457 are useful intermediates for the synthesis of various substituted benzoquinolizines [243, 244, 245b-c] this scaffold is found in many natural products [245b-d]. 

Reaction with inUnes derived from a-amino esters. In the presence of ZnCh (1 equiv.) the imine 1 derived from L-valine reacts with this diene to form 6-substituted 2,3-didehydro-4-piperidinones 2 and 3 with high diastereoselectivity (92 8). This reaction is believed to involve a Mannich reaction to form a, which undergoes Michael cyclization to form 2 and 3 in the ratio 92 8. 

---

See also in sourсe #XX -- [ ]

See also in sourсe #XX -- [ ]

---