Abstract
An attempted selective hydrogenation of 9:10-double bond of 3, 4-dihydro-9, 10-dehydro-(2′, 1′:1, 2-benzoquinolizinium) salts by means of Na2S2O4-Na2CO3 ended fruitless. In its stead ring cleavage took place, yielding N-β-phenethylpyridones with quantitative yield in smooth reaction. This clvaeage reaction appeared to be a base-induced one, since sodium hydroxide or silver oxide worked as well, whereas smooth cleavage was effected by sodium carbonate only in the presence of sodium dithionite, and the labile quinolinium hydrogen sulfite formed first as an intermediate seems to be prerequisite in this case. The selective hydrogenation was achieved with LiAlH4 in absolute ether. The compound thus produced (VIII) was found to be highly sensitive to oxidation, rapidly decolorizing on exposure to air.
