Abstract: 5-Hydro^-1, 9-dioxa-4, 6-diaza-5-phosphaspiro[4, 4]nonane(1) reacted with carbon bisulfide or isothiocyanates at room temperature in the presence of excessive ethyl alcohol to give 2-mercaptothiazoline (2) and 2-substituted iminothiazolidines (4_a) or aminothiazolines (4_b) respectively.The mechanism of this reaction might involve that compound 1 reacted with ethyl alcohol via the exchange ester route to form a three coordinated phosphorous compound, which then added to the unsaturated bond.

Key words: Spirophosphoranes, Isothiocyanates, Thiazolines, Thiazolidines