Synthesis of 4,5-Disubstituted-2-Piperidinones From 4-Piperidinones

Palladium-catalyzed cyclocarbonylation of unsaturated amines. Chemo- and stereoselective synthesis of N-heteroaryl γ- and δ-lactams

“…For example, only small amounts of the cis-isomer were formed (entries 5, and 6) or it was not formed at all (entries 1-4). Using the other amines, bearing a β-or a γ-aza heterocycle (4, 5), or those not having an aza group in the nitrogen substituent (6 and 7), the percentage of the δ-lactam decreased, sometimes in a significant way (entries 10 and 14), while the γ-lactam yield increased (entries [7][8][9][10][11][12][13][14]. Furthermore, the trans-/cis-ratio within the γ-lactams became almost unity, even by changing the solvent and the ligand.…”

“…[1][2][3][4][5] Its importance has led many researchers to investigate new synthetic methodologies for the preparation of azetidinones, 5,6 pyrrolidinones 7-10 and piperidinones. 11,12 Among these preparations, particularly interesting is the metal-catalyzed When toluene was used as solvent and 1,4-bis(diphenylphosphino)butane (dppb) as ligand we recorded a regioselectivity towards the six-membered ring; moreover, in these conditions, the five-membered ring was formed in the two isomeric forms cis-and trans-with a certain diastereoselectivity (trans>cis). It was found, in addition, that the use of CH 2 Cl 2 as solvent and R(+)-2,2'-bis(diphenylphosphino)-1,1'-binaphthalene (binap) as ligand made the reaction regioselective towards the five-membered ring product.…”