Catalytic Enantioselective Aziridination of Alkenes Using Chiral Dirhodium(II) Carboxylates.

Abstract

-The enantioselective aziridination of alkenes with[N-(4-nitrophenylsulfonyl imino]phenyliodinane catalyzed by dirhodium (II) tetrakis[N-tetrachlorophthaloyl-(S)-tert-leucinate], Rh 2 (S-TCPTTL) 4 , is described.While such enantioselectivities are highly dependent on the properties of the alkenes, 2,2-dimethylchromene was found to be a particularly suitable substrate which can be efficiently transformed into the aziridine product in 98% yield with 94% ee.The enantioselective nitrene transfer reaction from [N-(arylsulfonyl)imino]phenyliodinanes to alkenes catalyzed by chiral transition metal complexes represents one of the most direct and powerful methods for the construction of optically active aziridines which are versatile building blocks for the synthesis of biologically important, nitrogen-containing molecules.11 Over the past fifteen years, substantial progress has been made in the development of enantioselective variants through catalysis by copper,

Comparing various chiral dirhodium tetracarboxylates in the dirhodium method

“…If this group rotates to a ''vertical'' orientation (Scheme 5, structure on the left), a steric interference with the endo-directed methyl of the tert.-group exists (double-headed arrow) increasing the energy of that conformation. Therefore, the phthalimido group prefers the ''horizontal'' position giving way for an easy approach of even weak ligands; analogous conformations have been mentioned by Hashimoto et al 15,16 A remarkable consequence of this phthalimido group orientation is the fact that it is optimally oriented to exert an anisotropy effect onto the approaching ligand molecule.…”

Chiral Dirhodium(II) Carboxylates: New Insights into the Effect of Ligand Stereo-Purity on Catalyst Structure and Enantioselectivity

“…Their remarkable selectivity has reached a stage where they can function as a powerful tool in building up value added molecules with complex structures [7,[15][16][17][18][19][20][21][22][23][24][25][26][27][28][29][30][31][32][33][34].…”

On the Structure of Chiral Dirhodium(II) Carboxylate Catalysts: Stereoselectivity Relevance and Insights

“…This immense interest originates from their exceptional ability to effectively catalyze a broad spectrum of reactions with high levels of chemo-, regio-and stereo-selectivity. These transformations involve aziridinations [16][17][18], C-H insertions [7,19,20], ylide transformations [21][22][23][24][25], Lewis acid-promoted reactions [21,[26][27][28][29][30], cross-coupling reactions [31], cyclopropanation and cyclopropenation reactions [32][33][34][35]. In fact, they have proven their potential, particularly, in the field of asymmetric synthesis.…”