Ligand-free copper powder-catalyzed and KOtBu-accelerated expeditious synthesis of substituted benzoxazoles

Copper-catalyzed domino synthesis of ynamines

The hitherto unexplored N-alkynylation of electron-withdrawing or protecting group free N-heteroarenes such as indole, carbazole and pyrrole was developed using gem-dibromoalkenes to synthesize ynamines under ligand-free copper-catalyzed domino conditions. The development methodology of ynamines was also applied in the synthesis of enynamines, multi-coupled bis-ynamines, tris-ynamines, and the natural product peyonine, demonstrating its broad synthetic scope and applications.

Cu(II)/Vasicine Promoted Intramolecular C-O Formation: Synthesis of Benzoxazoles in EtOH

AIMS AND OBJECTIVES

Benzoxazoles are valuable bicyclic aromatic compounds; the construction of benzoxazoles via C-O cross-coupling reactions has attracted more and more attention.

MATERIALS AND METHODS

The best condition of C-O bond formation from o-haloanilides was carried out, taking Cu(OTf)₂ (5 mol%) and vasicine (10 mol%) as the catalysts in EtOH in the presence of K₂CO₃ (2 eq.) for 12 h at 90°C.

RESULTS

A series of 2-substituted benzoxazoles have been prepared in high yields from 2-bromoanilides and 2- iodioanilides under mild conditions.

CONCLUSION

We have developed an efficient Cu-vasicine catalytic system for intramolecular C-O bond formation. This strategy is applicable to the synthesis of a wide variety of 2-substituted benzoxazoles by intramolecular O-arylation of o-haloanilides.

Efficient Cu-catalyzed intramolecular O-arylation for synthesis of benzoxazoles in water

An efficient method was developed for synthesis of benzoxazoles by Cu-catalyzed intramolecular O-arylation of o-halobenzanilides in water. This strategy provides several advantages, such as high yields, water as a green solvent and functional groups tolerance.

An efficient method was developed for synthesis of benzoxazoles by Cu-catalyzed intramolecular O-arylation of o-halobenzanilides in water.

From simple quinoxalines to potent oxazolo[5,4-f]quinoxaline inhibitors of glycogen-synthase kinase 3 (GSK3)

2,7-Disubstituted oxazolo[5,4-f]quinoxalines were synthesized from 6-amino-2-chloroquinoxaline in four steps (iodination at C5, substitution of the chloro group, amidation and copper-catalysed cyclization) affording 28 to 44% overall yields. 2,8-Disubstituted oxazolo[5,4-f]quinoxaline was similarly obtained from 6-amino-3-chloroquinoxaline (39% overall yield). For the synthesis of other oxazolo[5,4-f]quinoxalines, amidation was rather performed before substitution; moreover, time-consuming purification steps were avoided between the amines and the final products (38 to 54% overall yields). Finally, a more efficient method involving merging of the last two steps in a sequential process was developed to access more derivatives (37 to 65% overall yields). Most of the oxazolo[5,4-f]quinoxalines were evaluated for their activity on a panel of protein kinases, and a few 2,8-disubstituted derivatives proved to inhibit GSK3 kinase. While experiments showed an ATP-competitive inhibition on GSK3β, structure-activity relationships allowed us to identify 2-(3-pyridyl)-8-(thiomorpholino)oxazolo[5,4-f]quinoxaline as the most potent inhibitor with an IC50 value of about 5 nM on GSK3α.

Synthesis of benzoxazoles via the copper-catalyzed hydroamination of alkynones with 2-aminophenols

We describe herein the synthetic method to benzoxazole derivatives via the copper-catalyzed hydroamination of alkynones with 2-aminophenols.

N-Heterocyclic carbene copper(i) complex-catalyzed synthesis of 2-aryl benzoxazoles and benzothiazoles

A new an efficient synthesis of 2-aryl benzoxazoles and benzothiazoles by intramolecular cyclization of 2-haloanilides/2-halothioanilides using a copper(i)-NHC complex is described.

Copper-catalyzed synthesis of benzoxazoles via tandem cyclization of 2-halophenols with amidines

This work reports a simple, efficient and alternative synthetic route for the preparation of benzoxazoles via tandem cyclization of 2-halophenols with amidines.

Intramolecular oxidative deselenization of acylselenoureas: a facile synthesis of benzoxazole amides and carbonic anhydrase inhibitors

A mild, efficient and one pot procedure to access benzoxazoles using easily accessible acylselenoureas as starting materials has been discovered.