4-Quinolone

4-Quinolone is an organic compound derived from quinoline. It and 2-quinolone are the two most important parent (meaning simplified) quinolones. 4-Quinolone exists in equilibrium with a minor tautomer, 4-hydroxyquinoline (CAS#611-36-9). Aside from pedagogical interest, 4-Quinolone is of little intrinsic value but its derivatives, the 4-quinolone antibiotics represent a large class of important drugs.[1]

The tautomeric equilibrium relating 4-quinolone (right) and 4-hydroxyquinoline (left)

4-Quinolone

Names
Other names 1H-Quinolin-4-one
Identifiers
CAS Number	529-37-3
3D model (JSmol)	Interactive image
ChEBI	CHEBI:155900
ECHA InfoCard	100.009.336
EC Number	210-268-2
PubChem CID	69141
UNII	M1O131WXFO
CompTox Dashboard (EPA)	DTXSID50209980
InChI InChI=1S/C9H7NO/c11-9-5-6-10-8-4-2-1-3-7(8)9/h1-6H,(H,10,11) Key: PMZDQRJGMBOQBF-UHFFFAOYSA-N
SMILES C1=CC=C2C(=C1)C(=O)C=CN2
Properties
Chemical formula	C9H7NO
Molar mass	145.161 g·mol^−1
Melting point	208–210 °C (406–410 °F; 481–483 K)
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
Infobox references

Synthesis

The chemical synthesis of quinolones often involves ring-closing reactions.[2] Such reactions often install a hydroxyl group (an –OH functional group) on the carbon across from the ring nitrogen (i.e., the C-4 positions). An example of such a synthesis is the Camps cyclization, which, depending on starting materials and reaction conditions, can give both 2-hydroxyquinolines (B) and 4-hydroxyquinolines (A) as shown. The hydroxyquinolines tautomerize to the quinolones.

The Camps cyclization, a quinoline synthesis giving 2- and 4-hydroxyquinolines.

References

1. Andriole, VT The Quinolones. Academic Press, 1989.
2. Shi, Pengfei; Wang, Lili; Chen, Kehao; Wang, Jie; Zhu, Jin (2017). "Co(III)-Catalyzed Enaminone-Directed C-H Amidation for Quinolone Synthesis". Organic Letters. 19: 2418–2421. doi:10.1021/acs.orglett.7b00968. PMID 28425721.