The oxidation and diels-alder reactions of N-methyl-3-isoquinolone1

✍ Scribed by Norbert J. Mruk; Howard Tieckelmann

• Publisher: Elsevier Science
• Year: 1970
• Tongue: French
• Weight: 206 KB
• Volume: 11
• Category: Article
• ISSN: 0040-4039
• DOI: 10.1016/s0040-4039(01)97948-1

✦ Synopsis

In the course of work on the alkylation of heterocyclic ambident anions2j3 we have studied 3-hydroxyisoquinoline (1) and its alkylated derivatives. N-Methyl-3-isoquinolone (2) has been previously described as being unstable4 and as deteriorating rapidly. 5 We report on the oxidation and Diels-Alder chemistry of this compound. Alkylation of (1) with methyl iodide in a solution of sodium methoxide and methanol gave (2) as a yellow viscous oil. Treatment of (2) with boiling benzene exposed to air gave the N-methyl homophthalimide derivatives (3) and (4). The melting point of (3) and its oxime agree with literature values. 697 Spectral data confirmed the structure of (3): IR (Nujol, microns), 5.79 (C=O), 5.85 (GO), and 5.97 (C=O); nmr (DMSO-d6), 3.25 ppm.(s, 3H, NCH3), 7.6-8.4 ppm., (m, 4H, aromatic protons): mass spectrum, molecular ion at m/e = 189. The diketohydroxyhomophthalimide (4), m.p. 177-179' (decomp.) gave satisfactory elemental analysis. Spectral data were as follows: IR (Nujol, microns), 3.08 (OH,sharp), 5.86 (GO), 6.00 (GO); nmr (DMSO-d6), 3.14 PPm. (s,3,NCH3), 5.87 ppm.(s, 1, Hi), 7.4-8.1 ppm. (m,4,aromatic protons): mass spectrum molecular ion at m/e = 191. When dry DMSO-d6 was used as the nmr solvent, the H4 proton appeared as a doublet at about 5.8 ppm. and the hydroxyl proton as a doublet at about 6.8 ppm. When slightly acidified D20 was added the two doublets collapsed and a sharp'singlet appeared at 5.87 PPm.