Design, preparation, and study of catalytic gated baskets.
We report a diastereoselective synthetic method to obtain a family of catalytic molecular baskets containing a spacious cavity (~570 Å(3)). These supramolecular catalysts were envisioned, via the process of gating, to control the access of substrates to the embedded catalytic center and thereby modulate the outcome of chemical reactions. In particular, gated basket 1 comprises a porphyrin "floor" fused to four phthalimide "side walls" each carrying a revolving aromatic "gate". With the assistance of (1)H NMR and UV-vis spectroscopy, we demonstrated that the small 1-methylimidazole guest (12, 94 Å(3)) would coordinate to the interior while the larger 1,5-diadamantylimidazole guest (14, 361 Å(3)) is relegated to the exterior of basket Zn(II)-1. Subsequently, we examined the epoxidation of differently sized and shaped alkenes 18-21 with catalytic baskets 12(in)-Mn(III)-1 and 14(out)-Mn(III)-1 in the presence of the sacrificial oxidant iodosylarene. The epoxidation of cis-stilbene occurred in the cavity of 14(out)-Mn(III)-1 and at the outer face of 12(in)-Mn(III)-1 with the stereoselectivity of the two transformations being somewhat different. Importantly, catalytic basket 14(out)-Mn(III)-1 was capable of kinetically resolving an equimolar mixture of cis-2-octene 20 and cis-cyclooctene 21 via promotion of the transformation in its cavity.
Department of Chemistry, The Ohio State University, Columbus, Ohio 43210, USA.
Bao-Yu
BY
Wang
Teodora
T
Žujović
Daniel A
DA
Turner
Christopher M
CM
Hadad
Jovica D
JD
Badjić