Synthesis of a High-Valent, Four-Coordinate Manganese Cubane Cluster with a Pendant Mn Atom: Photosystem II-Inspired Manganese–Nitrogen Clusters

High-valent, four-coordinate manganese imido- and nitrido-bridged heterodicubane clusters have been prepared and characterized by single-crystal X-ray diffraction and spectroscopic techniques. The title compound, a corner-nitride-fused dicubane with the chemical formula [Mn₅Li₃(μ₆-N)­(N)­(μ₃-N^<i>t</i>Bu)₆(μ-N^<i>t</i>Bu)₃(N^<i>t</i>Bu)] (<b>1</b>), has been prepared as an adduct with a nearly isostructural tetramanganese cluster with one Mn atom replaced by Li. An important feature of the reported chemistry is the formation of nitride from <i>tert</i>-butylamide, indicative of N–C bond cleavage facilitated by manganese

Synthesis of a High-Valent, Four-Coordinate Manganese Cubane Cluster with a Pendant Mn Atom: Photosystem II-Inspired Manganese–Nitrogen Clusters

High-valent, four-coordinate manganese imido- and nitrido-bridged heterodicubane clusters have been prepared and characterized by single-crystal X-ray diffraction and spectroscopic techniques. The title compound, a corner-nitride-fused dicubane with the chemical formula [Mn₅Li₃(μ₆-N)­(N)­(μ₃-N^<i>t</i>Bu)₆(μ-N^<i>t</i>Bu)₃(N^<i>t</i>Bu)] (<b>1</b>), has been prepared as an adduct with a nearly isostructural tetramanganese cluster with one Mn atom replaced by Li. An important feature of the reported chemistry is the formation of nitride from <i>tert</i>-butylamide, indicative of N–C bond cleavage facilitated by manganese

Enantioselective Synthesis of Cocaine C-1 Analogues using Sulfinimines (<i>N</i>-Sulfinyl Imines)

The first examples of cocaine analogues having substituents (methyl, ethyl, <i>n</i>-propyl, <i>n</i>-pentyl, and phenyl) at the C-1 position of the cocaine tropane skeleton were prepared by heating sulfinimine-derived α,β-unsaturated pyrrolidine nitrones. In the presence of the Lewis acid Al­(O<i>^t</i>Bu)₃ the nitrones undergo an intramolecular [3 + 2] cycloaddition to give tricyclic isoxazolidines that were transformed in three steps to the cocaine analogues. In the absence of the Lewis acid, lactams were formed resulting from rearrangement of the nitrone to an oxaziridine. A novel Pd- and base-promoted rearrangement of methanesulfonate salts of isoxazolidine to bridge bicyclic[4.2.1]­isoxazolidines was discovered

Enantioselective Synthesis of Cocaine C-1 Analogues using Sulfinimines (<i>N</i>-Sulfinyl Imines)

The first examples of cocaine analogues having substituents (methyl, ethyl, <i>n</i>-propyl, <i>n</i>-pentyl, and phenyl) at the C-1 position of the cocaine tropane skeleton were prepared by heating sulfinimine-derived α,β-unsaturated pyrrolidine nitrones. In the presence of the Lewis acid Al­(O<i>^t</i>Bu)₃ the nitrones undergo an intramolecular [3 + 2] cycloaddition to give tricyclic isoxazolidines that were transformed in three steps to the cocaine analogues. In the absence of the Lewis acid, lactams were formed resulting from rearrangement of the nitrone to an oxaziridine. A novel Pd- and base-promoted rearrangement of methanesulfonate salts of isoxazolidine to bridge bicyclic[4.2.1]­isoxazolidines was discovered

Enantioselective Synthesis of Cocaine C-1 Analogues using Sulfinimines (<i>N</i>-Sulfinyl Imines)

The first examples of cocaine analogues having substituents (methyl, ethyl, n-propyl, n-pentyl, and phenyl) at the C-1 position of the cocaine tropane skeleton were prepared by heating sulfinimine-derived α,β-unsaturated pyrrolidine nitrones. In the presence of the Lewis acid Al­(OtBu)3 the nitrones undergo an intramolecular [3 + 2] cycloaddition to give tricyclic isoxazolidines that were transformed in three steps to the cocaine analogues. In the absence of the Lewis acid, lactams were formed resulting from rearrangement of the nitrone to an oxaziridine. A novel Pd- and base-promoted rearrangement of methanesulfonate salts of isoxazolidine to bridge bicyclic[4.2.1]­isoxazolidines was discovered

Enantioselective Synthesis of Cocaine C-1 Analogues using Sulfinimines (<i>N</i>-Sulfinyl Imines)

The first examples of cocaine analogues having substituents (methyl, ethyl, <i>n</i>-propyl, <i>n</i>-pentyl, and phenyl) at the C-1 position of the cocaine tropane skeleton were prepared by heating sulfinimine-derived α,β-unsaturated pyrrolidine nitrones. In the presence of the Lewis acid Al­(O<i>^t</i>Bu)₃ the nitrones undergo an intramolecular [3 + 2] cycloaddition to give tricyclic isoxazolidines that were transformed in three steps to the cocaine analogues. In the absence of the Lewis acid, lactams were formed resulting from rearrangement of the nitrone to an oxaziridine. A novel Pd- and base-promoted rearrangement of methanesulfonate salts of isoxazolidine to bridge bicyclic[4.2.1]­isoxazolidines was discovered

Reactive Pendant MnO in a Synthetic Structural Model of a Proposed S₄ State in the Photosynthetic Oxygen Evolving Complex

The molecular mechanism of the Oxygen Evolving Center of photosystem II has been under debate for decades. One frequently cited proposal is the nucleophilic attack by water hydroxide on a pendant MnO moiety, though no chemical example of this reactivity at a manganese cubane cluster has been reported. We describe here the preparation, characterization, and a reactivity study of a synthetic manganese cubane cluster with a pendant manganese-oxo moiety. Reaction of this cluster with alkenes results in oxygen and hydrogen atom transfer reactions to form alcohol- and ketone-based oxygen-containing products. Nitrene transfer from core imides is negligible. The inorganic product is a cluster identical to the precursor, but with the pendant MnO moiety replaced by a hydrogen abstracted from the organic substrate, and is isolated in quantitative yield. ¹⁸O and ²H isotopic labeling studies confirm the transfer of atoms between the cluster and the organic substrate. The results suggest that the core cubane structure of this model compound remains intact, and that the pendant MnO moiety is preferentially reactive

Enantioselective Synthesis of Cocaine C-1 Analogues using Sulfinimines (<i>N</i>-Sulfinyl Imines)

The first examples of cocaine analogues having substituents (methyl, ethyl, <i>n</i>-propyl, <i>n</i>-pentyl, and phenyl) at the C-1 position of the cocaine tropane skeleton were prepared by heating sulfinimine-derived α,β-unsaturated pyrrolidine nitrones. In the presence of the Lewis acid Al­(O<i>^t</i>Bu)₃ the nitrones undergo an intramolecular [3 + 2] cycloaddition to give tricyclic isoxazolidines that were transformed in three steps to the cocaine analogues. In the absence of the Lewis acid, lactams were formed resulting from rearrangement of the nitrone to an oxaziridine. A novel Pd- and base-promoted rearrangement of methanesulfonate salts of isoxazolidine to bridge bicyclic[4.2.1]­isoxazolidines was discovered

Enantioselective Synthesis of Cocaine C-1 Analogues using Sulfinimines (<i>N</i>-Sulfinyl Imines)

The first examples of cocaine analogues having substituents (methyl, ethyl, <i>n</i>-propyl, <i>n</i>-pentyl, and phenyl) at the C-1 position of the cocaine tropane skeleton were prepared by heating sulfinimine-derived α,β-unsaturated pyrrolidine nitrones. In the presence of the Lewis acid Al­(O<i>^t</i>Bu)₃ the nitrones undergo an intramolecular [3 + 2] cycloaddition to give tricyclic isoxazolidines that were transformed in three steps to the cocaine analogues. In the absence of the Lewis acid, lactams were formed resulting from rearrangement of the nitrone to an oxaziridine. A novel Pd- and base-promoted rearrangement of methanesulfonate salts of isoxazolidine to bridge bicyclic[4.2.1]­isoxazolidines was discovered

Enantioselective Synthesis of Cocaine C-1 Analogues using Sulfinimines (<i>N</i>-Sulfinyl Imines)

The first examples of cocaine analogues having substituents (methyl, ethyl, <i>n</i>-propyl, <i>n</i>-pentyl, and phenyl) at the C-1 position of the cocaine tropane skeleton were prepared by heating sulfinimine-derived α,β-unsaturated pyrrolidine nitrones. In the presence of the Lewis acid Al­(O<i>^t</i>Bu)₃ the nitrones undergo an intramolecular [3 + 2] cycloaddition to give tricyclic isoxazolidines that were transformed in three steps to the cocaine analogues. In the absence of the Lewis acid, lactams were formed resulting from rearrangement of the nitrone to an oxaziridine. A novel Pd- and base-promoted rearrangement of methanesulfonate salts of isoxazolidine to bridge bicyclic[4.2.1]­isoxazolidines was discovered