ring closure reactions ring closure reactions O 0130 36 -075 Cyclization of Phenacyl 2-{[2,2-Di(ethoxycarbonyl)vinyl]amino}benzoate. -The thermal cyclization of the title compound (III) is achieved in Ph 2 O to afford quinolone (IV). The phenacyl group does not cyclize even on prolonged heating. Heating in sulfuric acid results in hydrolysis of the ethyl ester group furnishing the corresponding carboxylic acid (V). -(HRADIL, P.; KVAPIL, L.; HLAVAC, J.; LEMR, K.; SEVCIK, J.; Collect. Czech. Chem. Commun. 63 (1998) 4, 520-524; Farmak, CZ-771 17 Olomouc, Czech Rep.; EN)

A general and efficient synthesis of 4-substituted-1H-pyrazole-3,5-diamines was developed to access derivatives with an aryl, heteroaryl, or styryl group, which are otherwise relatively difficult to prepare. The first step is based on the Suzuki-Miyaura cross-coupling reaction utilizing the XPhos Pd G2 precatalyst. The coupling reactions of 4-bromo-3,5-dinitro-1H-pyrazole with the electron-rich/deficient or sterically demanding boronic acids enabled the production of the corresponding dinitropyrazoles. The subsequent iron-catalyzed reduction of both nitro groups with hydrazine hydrate accomplished the synthesis. The additional demethylation of the 4-methoxystyryl derivative allowed the production of the carboanalog of CAN508 reported as a selective CDK9 inhibitor.

The cyclization of phenacyl anthranilate has been studied with the aim to develop the synthesis of 2‐(2′‐aminophenyl)‐4‐phenyloxazole. However, a different course of the reaction than expected was observed. 2‐Phenyl‐2‐hydroxymethyl‐4‐oxo‐1,2,3,4‐tetrahydroquinazoline (3a) was formed by the reaction of phenacyl anthranilate (2) with ammonium acetate under various conditions. 3‐Hydroxy‐2‐phenyl‐4(1H)‐quinolinone (4) arose by heating compound 3a in acetic acid. The same compound was obtained by melting compound 3a, but the yield was lower. Different types of products resulted in the reaction of compound 3a with acetic anhydride. Under mild conditions acetylated products 2‐acetoxymethyl‐2‐phenyl‐4‐oxo‐1,2,3,4‐tetrahydroquinazoline (7a) and 2‐acetoxymethyl‐3‐acetyl‐2‐phenyl‐4‐oxo‐1,2,3,4‐tetrahydroquinazoline (8) were prepared. If the reaction was carried out under reflux of the reaction mixture, molecular rearrangement took place to give cis and trans 2‐methyl‐4‐oxo‐3‐(1‐phenyl‐2‐acetoxy)vinyl‐3,4‐dihydroquinazolines (9a and 9b). All prepared compounds have been characterised by their 1H, 13C and 15N NMR spectra, IR spectra and MS.

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