Diastereo- and Enantioselective Dearomatization of Rhenium-Bound Naphthalenes

Abstract

Dihapto-coordinated naphthalene complexes of the form TpRe(CO)(L)(eta(2)-naphthalene) (L = PMe(3), pyridine, or 1-methylimidazole) undergo electrophilic addition with dimethoxymethane and with various Michael acceptors to generate 1H-naphthalenium species. These naphthalenium complexes undergo intra- or intermolecular nucleophilic addition reactions with stabilized enolates, silyl ketene acetals, or enols to form the corresponding dihydronaphthalene complexes. Oxidative decomplexation generates the free dihydronaphthalene. When a resolved form of the rhenium dearomatization agent is used, these reactions can be performed enantioselectively. DFT calculations provide a useful guide in explaining the observed stereochemistry. Depending on reaction conditions, a Michael-Michael ring-closure sequence (MIMIRC) or a net [2 + 4] cycloaddition with the bound naphthalene is also observed, and the corresponding tricyclic molecules can be removed from the metal in high yield.

Charge donation to and dearomatization of benzene attending complexation: DFT estimates of binding energies of TpMXO(L) with benzene, for Tp = hydridotris(pyrazolyl) borate, MXO = MoNO, ReCO, and WNO, and L = ammonia, N‐methylimidazole, pyridine, phosphine, methyl isocyanide, and carbon monoxide

“…B3LYP overestimates the M-C distances considerably, while LSDA matches the experimental values well. As we saw in previous studies, 10 LSDA overestimates binding energies while B3LYP provides plausible values. However, we have found strong correlations between LSDA and B3LYP results.…”

Enantioenriched Molybdenum Dearomatization: Dissociative Substitution with Configurational Stability

“…However, complexes with lower hapticities are also known (e.g., η 4 , η 2 ), and in all cases, the reactivity of the arene is enhanced. Specifically, chiral π-basic complexes of the type {MTpL 1 L 2 } (where M = Re, W, Mo; Tp = hydridotris­(pyrazolyl)­borate) are capable of forming η 2 -coordinated adducts with arenes that can undergo electrophile-initiated organic reactions. − Through a combination of chiral recognition in the coordination event and stereoelectronic differentiation in the reaction with the electrophile, the chirality of the metal stereocenter is translated to the organic substrate (Scheme ). The stereochemistry of subsequent reactions is also guided by the position of the metal.…”

Michael–Michael Ring-Closure Reactions for a Dihapto-Coordinated Naphthalene Complex of Molybdenum

“…The resulting benzofuran skeleton was formed as a mixture of stereoisomers. Alternatively, ReTp­(CO)­(MeIm)­(η 2 -2-methoxynaphthalene) was found to undergo cyclization with methyl acrylate . In this case, the stereocenters set by the metal were lost once the organic was liberated due to an elimination of the methoxy group.…”

“…Alternatively, ReTp(CO)(MeIm)(η 2 -2-methoxynaphthalene) was found to undergo cyclization with methyl acrylate. 24 In this case, the stereocenters set by the metal were lost once the organic was liberated due to an elimination of the methoxy group. In none of these cases was a systematic study performed, nor was an A+B MIMIRC cyclization achieved.…”