Synthesis of pyrimido[1,6-a]quinoxalines via intermolecular trapping of thermally generated acyl(quinoxalin-2-yl)ketenes by Schiff bases

• Svetlana O. Kasatkina,
• Ekaterina E. Stepanova,
• Maksim V. Dmitriev,
• Ivan G. Mokrushin and
• Andrey N. Maslivets

Beilstein J. Org. Chem. 2018, 14, 1734–1742, doi:10.3762/bjoc.14.147

• 3-acylpyrrolo[1,2-a]quinoxaline-1,2,4(5H)-triones react regioselectively with Schiff bases under solvent-free conditions to form pyrimido[1,6-a]quinoxaline derivatives in good yields. Keywords: acyl(quinoxalin-2-yl)ketenes; cycloaddition; pyrimido[1,6-a]quinoxalines; Schiff bases; thermolysis

• intraocular pressure (IOP) [8] etc. (Figure 1). Pyrimido[1,6-a]quinoxalines are one of the most intriguing and unexplored structures representing isosteres of this scaffold. Only few synthetic procedures towards these compounds are described in the literature: heterocyclizations of α-chloroisocyanates with

• synthetic approach towards pyrimido[1,6-a]quinoxalines we looked through the procedures to their closest analogues – pyrido[1,2-a]quinoxalines, the synthesis of which has been explored more frequently [3][4][12][13][14][15][16][17][18][19][20][21][22][23][24][25][26][27][28][29][30][31][32][33][34][35][36