Carbene-Catalyzed Activation of 2-Aminobenzaldehyde for Access to Chiral Fluorescent Quinazolinone

[1,5]-Oxy/Thio/Azole Sigmatropic Rearrangement versus Indolyl-Spirocyclization: Tandem Reactions of 2-Azidobenzoate with Isocyanides for Accessing Quinazolin-4(3H)-ones

A general protocol for the synthesis of a variety of functionalized quinazolinones has been developed through a sequential Pd-catalyzed coupling/1,5-alkyloxy/thio/azole shift/6π electrocyclization reaction of isocyanides and 2-carbonylaryl azides. When 3-(2-isocyanoethyl)indoles were utilized, an unusual competitive reaction between [1,5]-shift and indole-spirocyclization was observed, which renders a modular synthesis of quinazolinones and spiroindolenine-3,3'-pyrrolo[2,1-b]quinazolinones in a highly chemoselective manner.

Catalytic enantioselective [3+2] and [4+2]-annulation of cyclic N-sulfonyl ketimines with γ- or δ-hydroxy-α,β-unsaturated ketones

A highly efficient asymmetric [3+2] and [4+2]-annulation of cyclic N-sulfonyl ketimines with γ- or δ-hydroxy-α,β-unsaturated ketones has been developed. This innovative reaction employs an organocatalytic approach, utilizing a hydrogen-bonding bifunctional squaramide-based catalyst. The process enables precise synthesis of chiral polyheterotricyclic oxazolidines and 1,3-oxazinane derivatives, revealing intricate structures with incorporated chiral quaternary centers. Remarkably, this method delivers high yields and exceptional enantioselectivities and diastereoselectivities, achieving up to 99% yield, >20 : 1 dr, and >99% ee.

Organocatalytic Enantioselective Synthesis of Polycyclic Benzosultams from 2-Amino-β-nitrostyrenes with Cyclic N-Sulfonyl Ketimines

A highly efficient enantioselective [4 + 2] cycloaddition of 2-amino-β-nitrostyrenes with cyclic N-sulfonyl ketimines has been developed. This reaction utilizes an organocatalytic approach, employing a multiple-hydrogen-bonding bifunctional squaramide-based catalyst. The process allows for the precise synthesis of chiral polycyclic benzosultams, showcasing intricate structures that incorporate chiral quaternary centers. Noteworthy outcomes of this method include high yields with excellent enantioselectivities and diastereoselectivities (up to 97% yield, 96% ee, and >20:1 dr).

Synthesis of Polycyclic Imidazolidinones via Cascade [3 + 2]-Annulation of β-Oxo-acrylamides with Cyclic N-Sulfonyl Imines

An Et3N-catalyzed cascade [3 + 2]-annulation of β-oxo-acrylamides with cyclic N-sulfonyl ketimines or sulfamate-derived imines is developed under mild reaction conditions, which provides a concise and efficient route to access valuable sultam- or sulfamidate-fused imidazolidinone derivatives in good to excellent yields (80-95% yields) with excellent diastereoselectivities (>20:1 drs). The current protocol features atom economy, a transition-metal-free process, and broad functional group tolerance. Moreover, the asymmetric variant of the [3 + 2]-cycloaddition reaction was achieved in the presence of diphenylethanediamine or quinine-based bifunctional squaramide organocatalysts C-1 and C-11, giving the corresponding chiral polycyclic imidazolidinones in 68-90% yields with 25-94% ees and >20:1 drs in all cases.