2-Methylisoquinolinium iodide

Treatment of the pyrazolium[4,3-r/][l,2,3]oxadiazolium diiodide 124 with -hydroxy- or /)-dimethylaminobenzalde-hyde yielded the pyrazolo[4,3-r/][l,2,3]oxadiazole styryl and azastyryl cyanines 83a and 83b in modest yields. Parallel reaction with -nitrosophenol furnished 83c. Reaction of 124 with 1-ethylquinolinium iodide afforded 84a directly. However, 3-anilinocarbomylmethyl-2,4-diethyl-(N-phenylcarbomylmethyl)pyrazolium(4,3-r/)[l,2,3]oxadiazolium diiodide 125 arising from reaction of 124 with diphenylformamidine in refluxing acetic anhydride, is the precursor to 84b which follows from subsequent reaction with 2-methylisoquinolinium iodide (Scheme 16) <1994MI905-1>. 

The reduction of 2-substituted-isoquinolinium salts has been reported by Torossian65 with potassium borohydride in water, by Mirza,68 and by Durmand et al.,87,68 using sodium borohydride in aqueous methanol to yield 1,2,3,4-tetrahydroisoquinolines. The reduction of the second double bond appears to arise from a mechanism similar to that leading to tetrahydropyridines from pyridinium ions (see Section I). Mirza66 (see also Bose60) found that the reduction of berberine (60) with sodium borohydride could be stopped at the 1,2-dihydro-intermediate (61), and Karrer and Brook70 showed that the 1,2-dihydroisoquinoline formed by the lithium aluminum hydride reduction of l-phenyl-2-methylisoquinolinium iodide (62) could be further reduced to the 1,2,3,4-tetrahydroisoquinoline (63) with sodium borohydride in methanol. Awe et al.71,72 and Huffman73... 

The methoxyl group was placed at C-ll (yohimban numbering) by analogy with harmine, but C-10 could not be excluded with certainty. However, it has since been shown that the spectrum of alstoniline chloride is similar to that of synthetic 3-(6-methoxy-3-methyl-2-indolyl)-2-methylisoquinolinium iodide (XXII), whereas the spectrum... 

Write a sequence of mechanistic steps to explain the conversion of 2-methylisoquinolinium iodide into... 

Isoquinolones. When N-methylisoquinolinium iodide (1) in f-butyl alcohol is treated with solid KOH and then oxygenated, N-methylisoquinolone (2) is obtained in 827o yield. The oxidation is believed to involve the pseudo base a. The choice of solvent is important, but the substituent on nitrogen does not affect the yield. Also, the reaction appears to be general for heterocyclic iminium salts. ... 

N-Methylisoquinolinium iodide allowed to react with 2,6-dichlorobenzaldehyde and NaBH4 in dimethylformamide 4-(2,6-didilorobenzyl)-2-methyl-1,2-di-... 

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