Studies on Organophosphorus Compounds XVIII^†. Oxidation of Tertiary Alicyclic Amines With Elemental Sulfur in Hexamethylphosphoric Triamide (HMPA). Oxidative Rearrangements of Hexahydroazepines and Octahydroazocines to Bis(3-Pyrrolyl)Polysulfides

By heating (100-160 °C) N-alkylsubstituted alicyclic amines, R-N(CH₂) (n = 4, 5, 6), with elemental sulfur in HMPA, oxidation of the amine ring afforded the corresponding thiolactams, 2. Thus N-benzylthiopyrrolidone, 2a (67%), N-(2-phenylethyl)-2-thiopyrrolidone, 2b (71%), N-benzyl-2-thiopiperidone, 2c (27%), N-(2-phenylethyl)-2-thiopiperidone, 2d (63%), N-methyl-e-thiocaprolactame, 2e (45%), and N-(2-phenylethyl)-e-thiocaprolactame, 2f (10%) were prepared. From oxidation of N-alkylhexahydroazepines and N-alkyloctahydroazocines were produced as the main products bis (1-alkyl-2-ethyl-3-pyrrolyl) polysulfides, 3, and bis (1-alkyl-2-(n-propyl)-3-pyrrolyl) polysulfides, 4, respectively. Reduction of these with Zn, HCl or LiAlH₄ followed by methylation (MeI) gave the corresponding 3-(methylthio)-pyrroles, 8 in 20-49% overall yields. 1-(2-Phenylethyl)-2-ethyl-3-mercaptopyrrole, 7, was isolated in 48% yield from reduction (Zn, HCl) of the corresponding dipyrrolyl polysulfide. 3, 4-Dithiolated pyrroles were recognized in most reactions and isolated in some cases. The structures of the pyrroles were established by ¹H NMR, ¹³C NMR, and MS.