Some aspects of selenium chemistry

Abstract

A procedure for the synthesis of heteroaromatic amine derivatives of binary phosphorus selenides, P?ééSe?éç.3 B, P?éäSe?éç.2 B', P?éäSe?éç.3 B'' and P?éäSe?éê.6 B'', is described. This series of compounds, with B=isoquinoline, B'=pyridine and 4-methylpyridine and B''= 4-ethylpyridine, has been characterized by elemental analysis, infrared and mass spectroscopy. The data are used to suggest that these binary phosphorus selenides probably have a cage structure similar to that of the isologous binary phosphorus sulfides. The infrared spectra of these binary phosphorus selenide amine derivatives show the perturbations which are characteristic of the coordinated amines. Further, the observation of a brand in the region assigned to the P-N stretching vibration suggests that the amines are coordinated to the phosphorus atoms of the P?éäSe?éç cage. The mass spectrometric fragmentation pathways which have been suggested for the binary phosphorus selenides are consistent with the proposed structures. The synthesis of 1-methyl-4-selenouracil and 1-ethyl-4-selenouracil by the direct selenation of the appropriate sulfur analog with P?ééSe?éà is described. The parameters which influence the efficiency of this reaction are discussed. The formation of 1-methyl-4-selenouracil and 1-ethyl-4-selenouracil was demonstrated unequivocally by ultraviolet and mass spectroscopy. The ultraviolet spectra of the 1-lkyl-4-substituted uracils show a bathochromic shift as the 4-oxo-substituent is progressively replaced by sulfur and selenium. The genesis of the mass peaks recorded in the spectrum of 1-ethyl-4-selenouracil is attributed to two substituent-conditioned fragmentation pathways..