In contrast to the well-studied asymmetric catalyzed synthesis of tetrahydroquinolines, the asymmetric methodologies toward 3,4-dihydroquinolin-2-ones are quite rare. Herein, the first asymmetric cascade reaction is reported between ethynyl benzoxazinanones and mixed-anhydrides generated from aryl acetic acids and pivaloyl chloride, based on synergistic catalysis. This allowed the formation of attractive 3,4-dihydroquinolin-2-ones bearing two vicinal chiral centers at C3 and C4 in high yields with excellent diastereo- and enantioselectivities. A plausible chiral induction model for this reaction was proposed. The utility of this methodology was exemplified by further elaboration of the cyclization products by removal of the N-protecting groups.
3,4-Fused
tricyclic indole scaffolds are ubiquitous in bioactive
natural products and pharmaceuticals. A new protocol for the synthesis
of 3,4-fused tricyclic indoles has been developed through cascade
carbopalladation and C–H amination with N,N-di-tert-butyldiaziridinone. The protocol
allows access to a range of 3,4-fused tricyclic indoles, including
those containing various linkers and fused with medium-sized rings.
Rucaparib can be synthesized via this reaction, providing an advantageous
synthetic method for the FDA-approved cancer medicine.
Asymmetric 1,6-addition of malonates to para-quinone methides has been developed by using amide-phosphonium salts derived from easily available chiral α-amino acids as bifunctional phase transfer catalysts. Stabilized para-quinone methides with various substituents on the phenyl ring were reacted with diphenyl malonates to give functionalized diaryl methines in excellent yields and high to excellent ee's. Furthermore, to show the utility of this methodology, a gram scale synthesis of an 1,6-addition adduct and its further elaboration into the key intermediate for synthesis of GPR40 agonists were also described.
A novel and straightforward approach
for the synthesis of tribenzo[b,d,f]azepines starting
from 2-iodobiphenyls and 2-bromoanilines has been developed. A wide
range of tribenzo[b,d,f]azepines were obtained in good to excellent yields via a cascade
intermolecular palladium-catalyzed C–H activation/dual coupling
reaction. C,C-palladacycles, which
are generated by C–H activation of 2-iodobiphenyls, should
be the reaction intermediates.
A Mannich reaction between N-Boc isatin imine and α,α-dicyanoolefin as well as subsequent oxidative cleavage of the malonic nitrile moiety were described.
A Pd-catalyzed trans-selective carbosilylation
reaction of alkynes has been developed. The trans-vinylpalladium species, generated through intramolecular syn-carbopalladation of alkynes and subsequent cis-trans isomerization, were captured by hexamethyldisilane
to form multisubstituted vinylsilanes. This reaction provides a useful
strategy for the stereoselective synthesis of isoquinolinone-containing
exocyclic tetrasubstituted vinylsilanes.
The first copper-catalyzed enantioselective propargylation of trialkyl methantricarboxylate with propargylic alcohol derivatives was developed. The tricarboxylate unit in the obtained adducts could be easily transformed into a malonate moiety by treating with in situ generated NaOEt in excellent yield without racemization.
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