Diastereoselective synthesis of CF3-dihydrobenzofurans by [4+1] annulation of in situ-generated CF3-o-quinone methides and sulfur ylides

Synthesis of 4-Hydroxy-5-phenylaminoimidazoles through a Three-Component Reaction of Sulfur Ylides, Nitrosobenzenes, and Amidines

A novel annulation reaction of amidines with sulfur ylides and nitrobenzenes has been developed, affording various novel 4-hydroxy-5-phenylaminoimidazoles in moderate to excellent yields. The 4-hydroxy-5-phenylaminoimidazoles have been further converted into α-ketoamide and imidazol-4-imine derivatives. Moreover, a plausible mechanism for this multicomponent reaction is proposed.

Expeditious synthesis of CF3-phenanthridones through a base-mediated cross-conjugated vinylogous benzannulation (VBA)

Herein, we report a mild, efficient, and rapid approach for the preparation of CF3-phenanthridones through a cross-conjugated vinylogous [4 + 2] benzannulation of easily accessible 4-methyl-3-trifluoroacetylquinolones and nitro-olefins. The present transformation is superior to previous approaches for obtaining CF3-phenanthridones, in that it proceeds exclusively with the assistance of a simple base, eliminating the need for transition metal catalysts or oxidants. The strong electron-withdrawing nature of the CF3-group present in the quinolone moiety promotes the formation of a reactive cross-conjugated vinylogous enolate.

C2-Arylated Indoles and Benzofurans through Formal (4 + 1) Annulation of N-Sulfonyl-2-aminobenzaldehydes and Salicylaldehyde Derivatives with Electron-Deficient Benzyl Chlorides

A two-step formal (4 + 1) annulation-dehydration reaction offers a convenient route to C2-arylated indoles and benzofurans. This reaction exploits the bifunctional reactivity of electron-deficient benzyl chlorides with N-sulfonyl-2-aminobenzaldehydes or salicylaldehyde derivatives. The reaction tolerates both electron-withdrawing and donating groups on the substituted aldehydes, as well as variation of electron-withdrawing groups at the para position of the benzyl chloride reagent. This work also identifies interesting byproducts resulting from the self-reaction of these benzyl chlorides under basic conditions.

Cross-conjugated vinylogous annulation of π-CF3-allyl Pd-complexes with 4-methyl-3-trifluoroacetyl-quinolones

Herein, we disclose the hitherto unknown cross-conjugated vinylogous annulation of π-CF3-allyl Pd complexes with 4-methyl-3-trifluoroacetyl-quinolones to access phenanthridones. The CF3 group in the Pd-π-allyl complex is key for exclusive γ-regioselectivity and further annulation. The solvent switch orchestrates the dihydro-phenanthridones (CH3CN) and hydroxy-phenanthridones (DMF) in good yields, and also showed excellent optoelectronic properties.

A reusable polymer anchored pyridine mediated formal [4 + 1] annulation reaction for the diastereoselective synthesis of 2,3-dihydrobenzofurans

We have developed a highly stereoselective formal [4 + 1] annulation reaction to construct trans-2,3-dihydrobenzofurans utilising in situ generated supported pyridinium ylide. This approach has excellent substrate versatility and gram-scale synthesis capability. Moreover, the polymer-anchored pyridine has been recovered and reused multiple times. The product has been transformed into valuable molecules.

A formal [4 + 1] cycloaddition reaction of Baylis–Hillman bromides with sulfur ylides: facile access to α-alkenyl lactones

A formal [4 + 1] cycloaddition reaction of Baylis–Hillman adducts with sulfur ylides has been developed for the first time.

Recent advances in the application of ylide-like species in [4+1]-annulation reactions: an update review

In this review, advances in [4+1]‐annulation reactions involving sulfonium, sulfoxonium and ammonium ylides, as well as diazo compounds and carbenes are summarized over the last 6 years. Newly emerged methods...

Water-Mediated Intramolecular Cyclization/Oxidation of α-Carbonyl Sulfur Ylides: Synthesis of Corey-Chaykovsky Reagent Type Heterocycles

A new class of Corey-Chaykovsky reagent type five-membered heterocycles with an oxosulfonium ylide moiety has been synthesized by the water-mediated intramolecular cyclization/oxidation of α-carbonyl sulfur ylides generated in situ from sulfonium salts under mild conditions.