Palladium-catalyzed stereoselective decarboxylative allylation of azlactones: access to (Z)-trisubstituted allylic amino acid derivatives

Abstract

A palladium-catalyzed stereoselective decarboxylative allylation of azlactones with vinyl methylene cyclic carbonates (VMCCs) as allyl precursors is developed. This method allows the formation of a series of trisubstituted allylic amino...

Tandem Allylic Amination/oxa-Michael Addition of Vinyl Methylene Cyclic Carbonates via Palladium-Organo Relay Catalysis

“…A 1,6-dioxa-3a-azaphenalene derivative 3p could be obtained in 90% yield from 2-aminobenzene-1,3diol 1p, in which four new bonds were formed. 11 Next, we focused our efforts on the synthesis of enantioenriched 3,4-dihydro-2H-benzo[b] [1,4]oxazines (Table 1). However, due to the existence of a background reaction catalyzed by palladium, the realization of the asymmetric version is expected to be relatively more difficult.…”

“…Next, cinchonidinederived squaramide VI acted as a bifunctional organocatalyst to promote the second intramolecular Michael addition reaction. In the proposed catalytic model TS-i, the Brønsted acid unit of squaramide catalyst VI captures the ketone of intermediate ii and the Brønsted base motif activates the hydroxyl group of 2-aminophenol via hydrogen bonding, and then the final 3,4-dihydro-2H-benzo[b] [1,4] Reaction conditions: 1 (0.3 mmol), 2a (0.45 mmol) and Pd(PPh 3 ) 4 (0.009 mmol, 3.0 mol %), Ligand (0.018 6.0 mol %) in solvent (6.0 mL) at rt for 12 h. b PG = tosyl. c PG = SO 2 (2-Np).…”

“…First, the reaction could be run at gramscale and maintained the corresponding high efficiency. Next, the carbonyl group of the final product could further undergo reduction, oximation, and nucleophilic addition to form a series of benzo[b] [1,4]oxazine derivatives 5-9.…”

“…Diastereoselectivity could also be achieved. Product derivatization showed that more benzo[b]- [1,4]oxazine derivatives could be obtained through several simple conversions. The development of more tandem reactions based on allylic substitution of dipoles is ongoing in our laboratory.…”

“…As one of the important zwitterionic allylpalladium precursors, vinyl methylene cyclic carbonates (VMCCs) were first developed by Zhi et al and employed in [3 + 2] cycloadditions. Subsequently, the research groups of Guo, Yuan, and Zhang further explored the reactivity of these VMCCs, respectively. At present, VMCCs have been utilized in [3+n] cycloadditions, [5+n] cycloadditions, allylic substitutions, and others (Scheme , a).…”