Palladium-Catalyzed Carbonylative [2 + 2] Cycloaddition for the Stereoselective Synthesis of Either cis- or trans-3-Alkenyl .beta.-Lactams

The Stereoselective Synthesis of Alkenyl‐β‐lactams by Palladium‐Catalyzed [2+2] Carbonylative Cycloaddition

“…According to previously reported data, [33,34] as well as the data in Table 1, the CO insertion would always occur between the carbon (C-3) directly attached to the halogen and the palladium (structure 17). When the halogen is not in the terminal position of the allylic chain, we found, instead, that the insertion occurs at the less hindered carbon atom (C-1) of structure 15.…”

“…Scheme 3 d) Palladium-catalyzed carbonylation of the allyl phosphate 4 in the presence of imines, under CO pressure. [33,34] The reaction is stereoselective since the formation of the trans-7 or the cis-8 β-lactam depends on the imine used for the coupling. An imine conjugated 6 with a carbonyl group gives the cis-β-lactam, whereas the unconjugated imine 5 gives the trans isomer (Scheme 4).…”

Application of diethyl ethynephosphonate for the synthesis of 3-phosphonylated β-lactams via Kinugasa reaction

“…1 H-NMR analysis of the crude product revealed the presence of a single product, which was identified as the trans-isomer on the basis of the HC(3)-HC(4) coupling constant of 2.1 Hz. 22 Analogously, β-lactams trans-6b-h with a benzyl, phenyl or methyl group at N(1) were obtained with complete diastereoselectivity and in good yields (Table 1). The type of substituent on the N-atom influences neither the reaction course nor the yield of the formed product.…”

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.…”