Bis 4-methylphenyl thio-1,3,2,4-dithiadiphosphetane 2,4-Disulfide

Thionation of Amides. 2,4-Bis[(4-methylphenyl)thio]-l,3,2, 4-dithiadiphosphetane-2,4-disulfide (1) reacts with carboxamides to give the corresponding thioamides. Usually, this thionation reaction is performed in a 1 1 mixture of toluene and pyridine at 70-110 °C. For example, the treatment of 7 2-dimethyl-7V-phenylpropanamide (2) with 1 in toluene/pyridine under reflux for ca. 15 h leads to thioamide 3 in 70% yield (eq 1). After only 3 h, 70% of the starting material (2) is consumed and 3 is obtained in 66% yield. 

Synthesis of ly3-Thiazole-5(4/ ft-thiones. The preferential thionation of /V,/V-disubstituted carboxamides can be used for a convenient synthesis of 2,4,4-trisubstituted l,3-thiazole-5(4/ -thiones of type 11. Treatment of Wacylated a,a-disubstituted a-amino acid amide 10 with 1 in toluene/pyridine at 100 °C gives 11 as the sole product. In contrast, the analogous reaction with Lawesson s reagent leads exclusively to the corresponding 1,3-thiazol-5(4/0-one 12 (eq 5).  

A list of General Abbreviations appears on the front Endpapers 

This difference can be rationalized by a reverse sequence of thionation of the diamide and the assumption that the analogs of 10 with a thiobenzoyl group undergo a spontaneous cyclization via elimination of dimethylamine to give 1,3-thiazole derivatives. 

Thionation of Lactams. The thionation of TV-substituted lactams with 1 in toluene/pyridine provides the corresponding thiolactams, e.g., TV-methylp)rrolidin-2-one (13) is transformed into TV-methylpyrrolidine-2-thione (14) (eq 6). The observed selectivity in the case of lactams is similar to that of amides the reaction of TV-unsubstituted lactams with 1 is sluggish, i.e., the product pyrrolidine-2-thione is formed in very low yield. 

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