Network topology and cavity confinement-controlled diastereoselectivity in cyclopropanation reactions catalyzed by porphyrin-based MOFs

Abstract

In this work, we show that the stereoselectivity of a reaction can be controlled by directing groups of substrates, by network topology and by local cavity confinement of metal–organic framework (MOF) catalysts.

Exploitation of Intrinsic Confinement Effects of MOFs in Catalysis

“…This situation is favored in the specific Kagomé topology of PCN‐222 in contrast to PCN‐224. The Rh–Rh distance between two neighboring centers is approximately 10 Å for PCN‐222, which coincides with the length of an amino‐functionalized styrene and the Rh‐carbene, thus, increasing the trans ‐isomer formation [28] . The effect of topology on catalytic performance has also been highlighted by Hupp, Farha et al.…”

“…Using this crystalline nanoreactor, an unexpected chemoselectivity towards the primary silanes in the insertion of a carbenoid into Si−H bonds is observed in contrast to conventional catalytic systems in homogeneous phase where tertiary silanes show the highest reactivity [24] . Besides affecting the chemoselectivity of a reaction, the MOF itself can also be applied to induce stereoselectivity [25–29] . In such cases, the porous environment itself has been exploited to control the diastereoselectivity of a reaction without bearing any further stereoinformation (i. e. no chiral auxiliaries).…”

Platinic metal porphyrins and hybrid nanomaterials embedding them as catalysts in chemical transformations

“…Cyclopropanation of double bonds is usually catalysed by transition metals, especially Rh (II, III) compounds. The proven stability, recyclability along with the pocket-like environment around the catalytically active metalloporphyrin centre motivated Fischer et al 20 to test Rh-porphyrin-containing metal-organic frameworks as heterogenous catalysts for the cyclopropanation of olefins with ethyl diazoacetate. The metal-organic frameworks were obtained from saponified tetra(p-methoxycarbonylphenyl)porphyrinato-Rh(III) chloride and ZrCl 4 [PCN-224(Rh)] and from [tetra(p-carboxyphenyl)porphyrin-Rh(III) chloride (Figure 9) and ZrCl 4 [PCN-222(Rh)] respectively, by solvothermal synthesis in benzoic acid as modulator.…”

Thermal defect engineering of precious group metal–organic frameworks: impact on the catalytic cyclopropanation reaction

“…2,[5][6][7][8][9] Sideproducts resulting from homocoupling of two carbenes or from C-H activation are known to occur. [10][11][12][13][14][15] The latter reaction requires two open metal sites (OMS) at the metal center and yields linear allyl species which are further denoted as linear products. A mechanistic summary assisting the conclusions from this paper is provided in the ESI.…”

“…[16][17][18][19][20][21] Consequently, the performance of some related materials has been studied in the cyclopropanation of styrene with ethyl diazoacetate (EDA) as test reaction. 12,[22][23][24][25] Many of these reports focused on the influence of tuning the local structure of the catalytically active centers on the catalytic activity. For instance, Buntkowsky et al studied rhodium-based coordination polymers with 2D sheet structure comprising Rh 2 -PWs interconnected with terephthalate linkers regarding the impact of linker side chains in this reaction.…”