Enantioselective Synthesis of 3,4-Disubstituted cis- and trans-1,2,5-Thiadiazolidine-1,1-dioxides as Precursors for Chiral 1,2-Diamines

Both, cis- and trans-3,4-disubstituted thiadiazolidines 5 and 6 can enantioselectively be obtained from thiadiazoles 2 which, in turn, are efficiently prepared from the respective 1,2-diketone by an improved protocol. An asymmetric ruthenium-catalyzed transfer hydrogenation followed by a diastereoselective hydride addition furnishes exclusively the cis-isomers 5 which, under acidic conditions, undergo a novel isomerization into the trans-isomers 6. These cyclic sulfamides can be transformed into 1,2-diamines as well as 2,3-diamino acids.

两种cis-和trans-3,4-二取代硫代唑烷酮5和6，均可通过从2-硫杂唑中高效制备得到的相应1,2-二酮，借助改进的工艺进行手性选择性地获得。通过不对称的钌催化转移氢化反应，随后进行立体选择性的氢化物加成，可提供仅有的cis-异构体5。在酸性条件下，这些异构体5经历一种新颖的异构化过程，转变为trans-异构体6。这些环状磺酰胺可以转化为1,2-二胺，以及2,3-二氨基酸。