Iridium and a Brønsted acid cooperatively catalyzed chemodivergent and stereoselective reactions of vinyl benzoxazinones with azlactones

Abstract

Under cooperative catalysis of iridium and a Brønsted acid, different C4-substituted azlactones react with vinyl benzoxazinones via a formal [4+2] cycloaddition or substitution reaction in a chemo- and stereoselective mode.

An Update of Transition Metal-Catalyzed Decarboxylative Transformations of Cyclic Carbonates and Carbamates

“…It was found that the utilization of the newly exploited chiral P,S-ligand and hydrogen bonding is the key to control the regioselectivity for this reaction. Apart from palladium catalysis, iridium/Brønsted acid co-catalytic system was applied for the preparation of quinolinones through a formal [4 + 2] cycloaddition by the Shi group [15]. Later, the same group developed a palladium-catalyzed cascade cyclization reaction of para-quinone methides and cyclic carbamates [16].…”

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

“…In case of ligands PCy 3 and dppp, both of them gave 3 aa in the same chemical yields (entries 3 vs. 4). In contrast with the former cases, the chemical yield of the [4 + 2] cycloaddition differently increased with the use of ligands dppb and dppf (entries 1-4 vs. [5][6]. Finally, we found that ligand PPh 3 worked most efficiently among all the checked ligands, and furnished product 3 aa in the highest chemical yield (entry 7).…”

“…2). Very recently, the research groups of Mukherjee and Shi separately disclosed the [4+2] cycloadditions of ethynyl‐ or vinyl‐substituted benzoxazinones with oxazol‐5‐(4 H )‐ones. Basically, the N ‐Ts substituent in the vinyl benzoxazinone scaffolds functions as the key structural requirement for the above‐mentioned elegant chemical transformations.…”

Recent Advances in Azlactone Transformations

“…Another important contribution concerning the preparation of dihydrocoumarin scaffolds (48) cycloaddition reactions between o-hydroxylstyrenes (44), which acts as oxa-diene precursors, and azlactones (45) through a cooperative catalysis approach; simultaneously employing a Brønsted acid catalysis (46) and Brønsted base catalysis (47) (Scheme 13). [34] The matched couple between chiral phosphoric acid and chiral guanidine catalysts on the substrates activation was the highlight of this work.…”

“…Recently, Shi and co-workers described a cooperative catalysis methodology, employing a iridium complex and a Brønsted acid, in the formal [4+2] cycloadditions between vinyl benzoxazinones (86) and azlactones (87), leading to 3,4-dihydroquinolin-2-one (88) in good to excellent yields (ranging from Scheme [44] During the reaction optimization, the authors observed that the use of iridium complex catalyst was superior to most approaches towards vinyl benzoxazinanones using palladium-based catalysts. Moreover, different substituted vinyl benzoxazinones (89) and 2-substituted azlactones (90 and 91) were well tolerated in the optimized reaction conditions.…”