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The reaction mechanism of methyl 2-diazo-2-phenylacetate (DIA) with 1-phenylpyrrolidine (An) cooperatively catalyzed by a dirhodium(II) complex and chiral spirophosphoric acid (SPA) has been studied with the aid of DFT methods. The results show that the nucleophilic attack of An at the in situ generated carbenoid is preferred to give a metal-associated enol intermediate. In addition, a stronger interaction between the dirhodium(II) complex and molecules such as the enol and chiral spirophosphoric acid is better for the asymmetric C–H insertion. This is due to the fact that a stronger interaction can restrict the chiral spirophosphoric acid around the dirhodium(II) complex. In this case, the dissociated enol can be captured by chiral spirophosphoric acid immediately to give the major S-enantiomer product. Otherwise, the dimerization of enol molecules will occur followed by a self-catalyzed process to give the racemic C–H insertion product. This finding should be important for the design of other related du...

A series of novel rare-earth-metal monoalkyl complexes incorporating partially rotation restricted [N,N]-bidentate indolyl ligands were synthesized and characterized, and their reactivities and catalytic activities were investigated. Treatment of [RE(CH2SiMe3)3(thf)2] with 1 equiv of 2-[(N-2,6-diisopropylphenyl)iminomethyl)]indole (2-(2,6-iPr2C6H3N═CH)C8H5NH) in toluene at room temperature afforded the rare-earth-metal monoalkyl complexes [η1:η1-2-(2,6-iPr2C6H3N═CH)Ind]2RE(CH2SiMe3)(thf) (Ind = indolyl; RE = Yb (1), Er (2), Y (3), Dy (4), Gd (5)) and the samarium complex [η1:η1-2-(2,6-iPr2C6H3N═CH)Ind]3Sm (6) via alkane elimination in good yields. Treatment of complex 2 or 3 with 1 equiv of PhSiH3 in toluene at 80 °C for 12 h afforded the dinuclear complexes {[μ-η6:η1:η1-2-(2,6-iPr2C6H3NCH2)Ind]RE[2-(2,6-iPr2C6H3N═CH)Ind]}2 (Ind = indolyl, RE = Er (7), Y (8)) in good isolated yields. Treatment of complex 2 or 3 with 1 equiv of amidine (2,6-iPr2C6H3)N═CHNH(2,6-iPr2C6H3) in toluene produced the correspondin...

The reaction of carbene insertion into the C–H bond of indole catalyzed by the Rh2(HCO2)4 complex has been investigated in detail through DFT calculations. Results indicate that the indole can proceed via a nucleophilic attack at the carbene first to generate a carbonium ylide intermediate followed by a [1,4]-proton transfer to give a free enol. In this case, the final C–H insertion product can be obtained through the self-catalyzed [1,3]-proton shift of enol. Alternatively, the nucleophilic attack can also involve the concerted formations of C–O and C–C bonds to produce an oxocarbonium ylide intermediate. The subsequent [1,2]-proton shift catalyzed by a molecule of enol is also energetically feasible to give the C–H insertion product. It indicates the coexistence of two distinct pathways for the C–H insertion reaction of indole. However, the ratio between them can be regulated by the substituents on both carbenoid and indole. For instance, the enol pathway is always dominant for the phenyl-substituted ca...

The reactions of AlMe3 or AlEt3 with 2-pyridyl- or indolyl-substituted imines were studied, leading to the formation of different organoaluminum complexes. While the reactions of the iminopyridine Cy[N═CMe-2-(C5H4N)]2 (L1) derived from 1-(pyridin-2-yl)ethanone and trans-1,2-cyclohexanediamine with AlEt3 gave the aluminum complex Cy[NC(Me)(Et)-2-(C5H4N)AlEt2]2 (1), in which the two ketimine groups of the ligand were transformed into the amido functionality through the addition of two ethyl groups, the reaction of L1 with AlMe3 afforded the aluminum complex Cy[NC(═CH2)-2-(C5H4N)AlMe2]2 (2) via a sp3 C–H activation with elimination of two methane molecules. The reactions of indolyl-2-aldimines (2-(RN═CH)C8H5NH (R = tBu (L2H), C6H5 (L3H), 2,6-Me2C6H3 (L4H)) with AlMe3 or AlEt3 afforded only the deprotonated indolyl aluminum complexes [2-(RN═CH)C8H5N]AlMe2 (R = tBu (3), C6H5 (4), 2,6-Me2C6H3 (5)) and [2-(2,6-Me2C6H3N═CH)C8H5N]AlEt2 (6), respectively. The structures of complexes 2–6 were characterized by spectr...

The insertion of a carbenoid into an N–H bond of an amine cooperatively catalyzed by a dirhodium catalyst and a spiro chiral phosphoric acid has been investigated in detail using density functional theory methods. Calculations indicate that the reaction begins with the nucleophilic amine attacking at the carbenoid, forming a metal-associated ammonium ylide first followed by a rapid proton transfer to afford a metal-associated enamine intermediate. Subsequently, the enamine intermediate dissociates from the metal and yield a more stable seven-membered-ring conformation via an intramolecular hydrogen-bond exchange. Formation of the enamine intermediate requires an overall barrier of 5.7 kcal/mol and is exergonic by 5.1 kcal/mol. Calculations demonstrated that, although the conversion of the achiral enamine into the N–H insertion product can be facilitated efficiently by the dirhodium catalyst through a two-step process, it can be compressed to a large extent. This is due to the more competitive decompositio...

A DFT study on the reaction of diazoacetate with primary allyl alcohol mediated by dirhodium catalyst has been carried out in detail. Calculations indicate that the major O–H insertion product can be obtained via either a [1,3]-proton shift of the free enol or a [1,2]-proton shift of the free oxonium ylide, which are regulated by the orientation of the ester group. In the case of a [1,3]-proton shift the reaction begins with the nucleophilic attack of the alcohol at the carbenoid, generating a metal-associated oxonium ylide followed by a [1,4]-proton shift to the adjacent carbonyl oxygen atom of the ester group, resulting in a metal-associated enol. Subsequently, its decomposition liberates a free enol intermediate. The whole process requires an overall barrier of 4.2 kcal/mol and is exergonic by 6.4 kcal/mol. The [1,3]-proton shift of the enol also readily provides the final O–H insertion product, which has a barrier of 11.7 kcal/mol using a three-alcohol cluster as catalyst. For the free oxonium ylide p...