Design and characterization of novel dirhodium coordination polymers – the impact of ligand size on selectivity in asymmetric cyclopropanation

Abstract

Three chiral dirhodium coordination polymers Rh2-Ln (n=1-3) have been synthesized via ligand exchange between dirhodium trifluoroacetate Rh2(TFA)4 and differently sized chiral dicarboxylic acids derived from L-tert-leucine. SEM images indicate that...

Self-Adaptive Dirhodium Complexes in a Metal–Organic Framework for Synthesis of N–H Aziridines

“…Due to their high performance in both activity and selectivity, dirhodium catalysts have played a prominent role in a diverse array of organic carbine transformations, including C–H activation, cyclopropanation, and aziridination. ,− Thus, the catalytic behavior of the representative Rh 2 -ZIF-8-3 was evaluated in the direct synthesis of N–H aziridines from olefins and O -(2,4-dinitrophenyl)­hydroxylamine (DPH). Interestingly, even though the coordinated sphere of the dirhodium site was sterically saturated with four equatorial esp groups and two axially bound 2-MeIm groups, Rh 2 -ZIF-8-3 was able to promote this reaction to the desired product, i.e., 1,2-cyclohexeneimine.…”

“…The heterogenization of dirhodium carboxylates is a general strategy to address this dilemma due to its simple separation, minimal waste, and easy scale-up operation. , These previously reported strategies can be divided into two classes, axial binding at axial rhodium sites and exchange of bridging ligands at equatorial positions (Scheme A). − Nevertheless, the exchange of bridging ligands is often challenging since the majority of bridging ligands of dirhodium catalysts have no functional groups that would be able to directly immobilize onto the solid supports. As a consequence, all of these protocols require an extra prefunctionalization or modification for either the support or dirhodium carboxylates to perform the heterogenization process.…”

Self-Supported Chiral Dirhodium Organic Frameworks Enables Efficient Asymmetric Cyclopropanation

“…b Theoretical contents were calculated for the ideal framework. 16,28 These peaks were also observed in the spectra of Rh 2 -MOCP-1 and Rh 2 -MOCP-2 since they own similar chemical groups with Rh 2 (S-Br-NTTL) 4 . Importantly, the spectrum of Rh 2 (S-Br-NTTL) 4 presents a small stretching vibration of around 1043 cm −1 , which is ascribed to the C−Br oscillation.…”

“…3-Diazooxindole was prepared according to a method previously described in the literature. 28 Synthesis of Rh 2 (S-Br-NTTL) 4 . N-4-Bromo-1,8-naphtaloyl-(S)-tert-leucine (S-Br-NTTL).…”

Preparation of Chiral Enantioenriched Densely Substituted Cyclopropyl Azoles, Amines, and Ethers via Formal SN2′ Substitution of Bromocylopropanes

“…Enantiomerically pure cyclopropane derivatives are ubiquitous, nature inspired [ 1 , 2 , 3 , 4 , 5 , 6 , 7 , 8 ] building blocks abundantly employed in organic synthesis [ 9 , 10 , 11 , 12 , 13 ], asymmetric catalysis [ 14 , 15 , 16 , 17 ], and medicinal chemistry [ 18 , 19 , 20 , 21 , 22 , 23 , 24 , 25 ]. These advanced synthons are typically accessed via diastereoselective 1,3-ring closure reactions [ 26 , 27 , 28 , 29 , 30 ] or asymmetric cyclopropanation [ 31 , 32 , 33 , 34 , 35 , 36 , 37 , 38 , 39 , 40 , 41 ]. A less established, complementary approach relies on chemo- and diastereoselective installation of additional substituents into pre-formed chiral or prochiral cyclopropanes [ 42 , 43 , 44 , 45 ].…”