Olefin Cyclopropanation by Radical Carbene Transfer Reactions Promoted by Cobalt(II)/Porphyrinates: Active‐Metal‐Template Synthesis of [2]Rotaxanes

Abstract

Supportinginformation and the ORCID identification number(s) for the author(s) of this article can be found under: https://doi.

Ru(II)Porphyrinate-Based Molecular Nanoreactor with Unusual Coordinative Properties and Extraordinary Chemical Selectivity in N–H Bond Carbene Insertion Reactions

“…The crystal structure (CDCC ID 1883084) of 7 (Figure 2) reveals a virtually flat porphyrin core which together with the aromatic backbone creates a central cavity with dimensions of 8.49 and 7.91 Å (centroid-to-centroid of the phenyl spacers and porphyrin centroid-to-midpoint of C26-C26 i bond on the phenanthrene moiety, respectively, with symmetry code: i = 1/2-x, y, z; see Supplementary Figure S1 for complete atom numbering). Such cavity dimensions in 7 are rather smaller than those observed for a similar but semi-rigid porphyrin-based macrocycle reported in our previous work 24,25 (cavity dimensions 10.30 and 8.40 Å). The angle between the porphyrin and the molecular aromatic loop mean planes is 62.12 o , which is smaller than the expected 90 o .…”

“…35 Congruently, 13 C NMR and FTIR analyses (Supplementary Figures S4 and S5, respectively) show one single resonance at  = 180.1 ppm and one stretching band (COstretch = 1926 cm -1 ) for the carbonyl axial ligand in the isolated product, thus confirming formation of one single complex. Such coordinative properties are not ubiquitous as performing the metalation reaction under the same conditions used for 7 but with our previously reported 24,25 semi-rigid and larger macrocycle as ligand yields the two expected isomers as revealed by 1 H NMR spectroscopy (for spectrum and chemical structures see Supplementary Figure S6). Therefore, the structural features of 7, which yield a hollow receptor with a relatively small central cavity, is most likely the reason for such selectivity in the metalation reaction.…”

“…The rich coordination chemistry of porphyrinates [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18] is useful in the design of macrocyclic receptors, in which the porphyrinate subunits are positioned on the top of molecular capsules to create hollow structures with well-defined cavities. [19][20][21][22][23][24][25][26][27][28] In such molecular architectures, one of the axial positions of the metallic center is shielded from the environment, while the other has unencumbered reactivity. This asymmetry between the two axial coordination sites of the porphyrinate subunit can be explored to introduce a steric bias in the binding modes of the receptor.…”

“…With such configuration of the ligands around the metal center, the internal coordination site of the porphyrinate-based receptor can bind nonbulky substrates to efficiently and selectively promote their reactions inside the central cavity. [23][24][25][26][27][28][29][30][31][32] Such versatile strategy has been explored in the active-metal template synthesis of interlocked molecules, [24][25][26][27] asymmetric catalysis 28,29 and biomimetics. [30][31][32] However, in those applications, the porphyrinate-based macrocycles has virtually the same reactivity as their acyclic analogues.…”

Organocobalt Complexes as Sources of Carbon-Centered Radicals for Organic and Polymer Chemistries

“…Very recently, Megiatto et al elegantly adapted the cyclopropanation of olefins catalyzed by Co II (por) to the synthesis of rotaxanes from diazo compounds and styrene derivatives, by a radical-carbene-transfer reaction. 160 The process involved the design of a novel Co II (por)-macrocycle, with the macrocycle creating an asymmetry on the two axial positions of Co II (por) due to steric hindrance. In the presence of a bulky pyridine, the selective coordination of this ligand occurred only outside the cavity of the macrocycle.…”