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

Abstract

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.

Imino Transfer Hydrogenation Reductions

“…Preferential reduction of one C=N is observed but the other can be stereoselectively reduced using lithium borohydride; the products were transformed into chiral diamines ( Figure 25). [95] Asymmetric aziridines can be prepared by ATH of an azirine; this was one of the earliest reported applications of the use of Ru(II) complexes, achieved using a bicyclic amino alcohol ligand (Scheme 26). [96] The application of Rh(III) systems to the reduction of N-phosphinoyl imines has been described in depth by researchers from Avecia, who were able to obtain some very valuable insights into the mechanism of the reaction and requirement for removal of carbon dioxide during the reaction.…”

Solvent-Free Condensation Reactions To Synthesize Five-Membered Heterocycles Containing the Sulfamide Fragment

“…It can be concluded that the best procedure to synthesize 3a is procedure B/C, MPA 300 °C , 2/1a and MPA/1a molar ratios 1.3 and 0.11, respectively, at 70 °C (entry 5). This work resulted in an improved yield of 3a compared to that reported in the literature (51%, 13 87%, 16 or 66% 17 ). The reaction times in solvent-free reactions catalyzed by MPA are longer than those measured following the guidelines in refs.…”

“…[10][11][12] For the preparation of 3,4-disubstituted 1,2,5-thiadiazole 1,1-dioxide derivatives, the more general reaction is the condensation of the 1,2-dicarbonyl compounds 1 with sulfamide (2) (Scheme 1) in solution catalyzed by strong mineral acids. [13][14][15] To overcome the use of strong acids, an efficient and mild access to these 1,2,5-thiadiazole heterocycles using N,N′bis(trimethylsilyl)sulfamide and 1 promoted by BF 3 •OEt 2 was recently reported by Zezschwitz et al 16 Also, Erturk and Bekdemir 17 performed a microwave-assisted synthesis for the condensation reaction of 1 with 2 in absolute EtOH.…”

Bis(triphenylphosphine)iminium Salts of Dioxothiadiazole Radical Anions: Preparation, Crystal Structures, and Magnetic Properties

“…Dioxothiadiazole-based electroactive molecules [27][28][29][30][31][32][33] and their complexes [34], on the other hand, are still underrepresented, despite their obvious advantages: easy reduction to a stable radical form, good coordination abilities (including bridging mode) and chemical tunability presented here for the first time. In 2011, Awaga et al studied [1,2,5]thiadiazole [3,4-f][1,10]phenanthroline 1,1-dioxide (L) in context of its electrochemical properties and synthesis of radical salts [35].…”