Synthesis of a 6-CF3-Substituted 2-Amino-dihydro-1,3-thiazine β-Secretase Inhibitor by N, N-Diethylaminosulfur Trifluoride-Mediated Chemoselective Cyclization.

The synthesis of a 6-CF3-substituted 2-amino-dihydro-1,3-thiazine via N, N-diethylaminosulfur trifluoride (DAST)-mediated cyclization of N-hydroxypropyl thiourea 6 is described. This reaction gave 6-CF3-1,3-thiazine 7 with high chemical yield and chemoselectivity, suppressing the common byproduct of oxazine 8. This new protocol enabled access to 6-CF3-substituted 1,3-thiazine β-secretase inhibitor 2.