Reduction of some Cyclic Amides by Lithium Aluminium Hydride

Abstract

ON reduction by lithium aluminium hydride, amides usually give amines¹: it has now been found that N-methyl phenanthridones behave rather differently, yielding quaternary (phenanthridinium) compounds. Phenanthridones are reduced to phenanthridines. Thus, N-methyl phenanthridone and N-3-dimethyl phenanthridone (m.p. 139°; found: C, 80.6; H, 5.8; N, 6.15 per cent; calc. for C₁₅H₁₃ON: C, 80.7; H, 5.8; N, 6.3 per cent) reduced in ethereal solution on the 300-mgm. scale gave respectively 60 and 55 per cent yields of the quaternary iodides (3-methyl phenanthridine methiodide, m.p. 278°; found: C, 53.8; H, 4.1; N, 4.5; I, 37.4 per cent; calc. for C₁₅H₁₄NI: C, 53.75; H, 4.2; N, 4.18; I, 37.9 per cent). The analogous N-methyl quinolone likewise gave N-methyl quinolinium chloride (identified as its platinichloride), but the reaction was less easy, two hours refluxing in dibutyl ether giving a 20 per cent yield. Among the reduction products of N-methyl pyridone, only a trace of quaternary compound (isolated as picrate) was found, together with methylamine (7 per cent isolated as the platinichloride).