Catalytic Asymmetric Construction of the Tryptanthrin Skeleton via an Enantioselective Decarboxylative [4 + 2] Cyclization

Abstract

The first catalytic asymmetric construction of the tryptanthrin skeleton has been established, taking advantage of a palladium(0)/chiral ligand-catalyzed enantioselective decarboxylative [4 + 2] cyclization of vinyl benzoxazinanones with isatins. This reaction has not only provided a direct and efficient method for constructing chiral tryptanthrin skeleta in high yields and excellent enantioselectivities (up to 97% yield, >99% ee) but also represents the first catalytic asymmetric decarboxylative cyclization of vinyl benzoxazinanones with isatins.

Palladium‐Catalyzed Decarboxylative Asymmetric Allylic Alkylation: Development, Mechanistic Understanding and Recent Advances

“…Shi reported the asymmetric construction of the trypanthrin skeleton utilizing the decarboxylative [4+2] cyclization strategy (Scheme A) . Vinylbenzoxazinanones 280 underwent Pd‐catalyzed decarboxylation to form the Pd‐polarized aza‐ o ‐xylylenes that were intercepted by the amide N–H of the isatins 281 at the internal carbon of the allyl fragment.…”

Formal [4+2] Cycloaddition of Vinyl Benzoxazinones with Oxazol‐5‐(4H)‐Ones for Diastereoselective Construction of 3,4‐Disubstituted Dihydro‐2(1H)‐Quinolinones

“…Up to now, the vinyl benzoxazinones bearing a N-H moiety have rarely been chosen as a building block in the cycloaddition. [7] So, the development of their novel cycloadditions is highly demanded for the construction of structurally varying heterocycles.…”

Non‐Bonding Interactions Enable the Selective Formation of Branched Products in Palladium‐Catalyzed Allylic Substitution Reactions

“…In the same year, Mei, Shi, and co‐workers reported a nice example of an asymmetric decarboxylative allylic‐amination/cyclization reaction of vinyl benzoxazinanones 49 with isatins 50 in the presence of [Pd 2 (dba) 3 (CHCl 3 )] and chiral spiro ‐phosphorus ligand L8 (Scheme ). This reaction provided a range of tryptanthrins ( 51 ) in good yields with high chemo‐ and enantioselectivities.…”