Enantioselective fluorinating agents, (R)- and (S)-N-fluoro-3-tert-butyl-7-nitro-3, 4-dihydro-2H-benzo[e][1, 2]-thiazine 1, 1-dioxides (BNBT-F, 2) are readily prepared in 3 steps from racemic 3-tert-butyl-7-nitro-3, 4-dihydro-2H-benzo[e][1, 2]thiazine 1, 1-dioxides (5) via optical resolution and fluorination. These agents make accessible both enantiomers of optically active quaternary α-fluoro carbonyl compounds in modest to high enantioselectivities. X-ray crystallographic analysis of chiral 2 reveals a unique structure wherein the nitrogen atom is highly pyramidalized and fluorine occupies an axial position.
通过光学分离和
氟化,可以从外消旋3-叔丁基-7-硝基-3,4-二氢-2H-苯并[e][1,2]
噻嗪1,1-二氧化物(5)通过3个步骤轻松制备出手性
氟化剂(R)-和(S)-N-
氟-3-叔丁基-7-硝基-3,4-二氢-2H-苯并[e][1,2]
噻嗪1,1-二氧化物(B
NBT-F,2)。这些试剂可以以中等至高度的手性选择性获得光学活性四元α-
氟羰基化合物的两种对映异构体。对手性2进行X射线晶体学分析,可以发现一种独特的结构,其中氮原子高度锥形化,
氟占据轴向位置。