one 0 6 g 0 0025 mol 2 fluoro 3 trifluoromethylbenzaldehyde 0 5 g 0 0025 mol and methyl 3 aminocrotonate 0 3 g 0 0025 mol and dioxane 30 ml were heated to 110 u00b0 c for 40 hours the solvent was removed in vacuo and the resulting oil purified on sio 2 eluting with 40 hexanes in ethyl acetate the product compound 22 was isolated as a white solid 0 37 g 28 yield anal calc 39 d for c 19 h 19 f 4 no 7 s 2 c 44 44 h 3 73 n 2 73 found c 44 32 h 3 78 n 2 52 1 1 5 5 tetraoxide 1 5 dithiocan 3 one 0 3 g 0 0013 mol 3 nitrobenzaldehyde 0 2 g 0 0013 mol 2 n methyl n methylphenyl aminoethyl 3 aminocrotonate 0 33 g 0 0013 mol and dioxane 15 ml were heated to 101 u00b0 c for 24 hours the solvent was removed in vacuo and the resulting oil purified on sio 2 eluting with 50 hexanes in ethyl acetate the resulting oil was dissolved in ethyl acetate and hydrogen chloride gas was bubbled through the solution the resulting precipitate was filtered and washed wiih ether the product was compound 25 0 11 g 13 yield anal calc 39 d for c 27 h 31 n 3 o 8 s 2 0 5 h 2 o.