Mixed electrolytic reduction of 1,4-dimethylpyridinium methyl sulfate with acetone and of 1-methylpyridiniummethyl sulfate with cyclopentanone

Some time ago we described 1 mixed electrolytic reduction of some pyridine bases with ketones and mixed electrolytic reduction of 1,4-dimethylp yridinium methyl sulfate with acetone and methyl ethyl ketone. In this paper we discuss mixed electrolytic reduction of 1,4-dimethylp yridinium methyl sulfate with acetone in greater detail and, further, the similar reduction of 1-methylpyrid inium methyl sulfate with cyclopentanone. In the first case we obtained after electrolytic reduction on lead electrodes in dilute sulfuric acid a mixture of products from which we isolated by distillation and preparative gas chromatography 1,4-dimethylpiperidine (la), l,4-dimethyl-3-piperideine (Ha), 2-isopropenyl-l,4-dimethyl-3-piperideine (Ilh), 2-(2-hydroxy-2-propyl)-l,4-dimethyl-3-piperideine (Ili), l,4-dimethyl-6-(2-hydroxy-2-propyl)-3-piperideine (Illi), l-methyl-4-tert-butyl-3-piperideine (IIj), <- 2,5,7,7-tetramethyl-2-aza-6-oxabicyclo[3,2.l]-octane (IV), and eventually a mixture of tricyclic compounds, most probably 1,1': 4,4'-tetramethyl-2,2': 4,4'-bipiperidylene (V) and 1,1': 4,4'-tetramethyl-2,4': : 4,2'-bipiperidylene (VI). Substance Ilj is formed probably by a Wagner-Meerwein rearrangement of 4-(2-hydroxy-2-propyl)-1,4-dimethylpiperidine (IXa), which we could not detect in the reaction mixture in this case; however, in the case of a similar mixed electrolytic reduction of l-ethyl-4-methylpyridiniumethyl sulfate alcohol IXb was isolated2. The structure of the bicyclic compound IV followed from its elemental analysis and the analysis of IR and NMR spectra. In the case of a mixture of compounds formed by dimerization of l,4-dimethyl- 3-piperideine or of some of its precursor we cannot exclude the structure formed by connection of the positions, * PartXLIX in the series Studies in Pyridine Series; Part XLVIII: This Journals, 1571 (1975).