Rearrangement of 7-Aryloxazolo[5,4-b]pyridines to Benzo[c][1,7]naphthyridine-4(3H)-ones and Thieno[3,2-c][1,7]naphthyridine-6(7H)-ones

Abstract

In this work, we describe the development of the rearrangement for 7-aryl-substituted oxazolo [5,4-b]pyridines treated with aluminum chloride into synthetically hard-to-reach benzo [c][1,7]naphthyridinones. The discovered rearrangement is applied to a variety of electron-rich (hetero)arene substrates. It offers the advantages of mild conditions (90 °C temperature), fast reaction rates (<4 h), compatibility with air moisture, and the use of inexpensive commercial reagents. The proposed reaction mechanism and key elementary reaction acts were studied in detail using quantum chemical calculations. The photophysical properties of the synthesized compounds were studied by steady-state UV−vis spectroscopy.

New Synthesis of Pyrazolo[3,4-b]pyridine Derivatives Based on 5-Aminopyrazole and Azlactones

“…As we previously reported, 7-aryloxazolo [5,4-b]pyridines or 4phenylbenzo[d]oxazoles are capable of rearrangement into benzo[c] [1,7]naphthyridin-4(3H)-ones or phenanthridin-4-ols when reacted with aluminum chloride. 3a,12a,b Oxazolo[5,4b]pyridine derivatives annulated at C(5)-C(6) position were not introduced into this reaction. We have found that heating oxazolo [5,4-b]pyrazolo [4,3-e]pyridines 5a-c, f-i in chlorobenzene to 130°C with a twofold excess of anhydrous AlCl3 leads to the formation of previously unknown benzo [c]pyrazolo [4,3-f] [1,7]naphthyridin-5-ones 7a-c, f, g, pyrazolo [4,3-f]thieno [3,2-c] [1,7]naphthyridin-6-one 7h or furo [3,2-c]pyrazolo [4,3-f] [1,7]naphthyridin-6-one 7i with yields of 42-82% (Scheme 3).…”

Easy Route to New Fused Dihydroisoquinoline-Naphthyridinone Frameworks

“…It should be noted that the resulting benzo[c][1,7]naphthyridine system has not been synthesized until recently. 41,42 Scheme 2. Synthesis of benzo[c]isoquinoline[1,2-g][1,7]naphthyridine-5,7-diones 11a-f.…”

“…It should be noted that the resulting benzo[c] [1,7]naphthyridine system has not been synthesized until recently. 41,42 Compounds 11a-f are poorly soluble in most organic solvents. In their 1 Н and 13 С NMR spectra, recorded in deuterotrifluoroacetic acid, there are no С(15)-H signals.…”

“…It should be noted that the resulting benzo[ c ][1,7]naphthyridine system has not been synthesized until recently. 41 42…”

Synthesis of 3‐Aminopyrido[2,1‐a]isoquinolin‐4‐one Derivatives via Condensation of Azlactones with 1‐Alkyl‐3,4‐dihydroisoquinolines

“…In clinical practice, 5‐amino‐[3,4′‐bipyridin]‐6(1 H )‐one 4 , known as the cardiotonic drug Amrinone, is used [17] . In addition, 3‐aminopyridin‐2(1 H )‐ones are used in the synthesis more complex biologically active compounds [18a–m] …”