Samarium-based Grignard-type addition of organohalides to carbonyl compounds under catalysis of CuI

Use of carboxymethyl cellulose as binder for the production of water-soluble catalysts

Bio-based polymers are materials of high interest given the harmful environmental impact that involves the use of non-biodegradable fossil products for industrial applications. These materials are also particularly interesting as bio-based ligands for the preparation of metal nanoparticles (MNPs), employed as catalysts for the synthesis of high value chemicals. In the present study, Ru (0) and Rh(0) Metal Nanoparticles supported on Sodium Carboxymethyl cellulose (MNP(0)s-CMCNa) were prepared by simply mixing RhCl3x3H2O or RuCl3 with an aqueous solution of CMCNa, followed by NaBH4 reduction. The formation of MNP(0)s-CMCNa was confirmed by FT-IR and XRD, and their size estimated to be around 1.5 and 2.2 nm by TEM analysis. MNP(0)s-CMCNa were employed for the hydrogenation of (E)-cinnamic aldehyde, furfural and levulinic acid. Hydrogenation experiments revealed that CMCNa is an excellent ligand for the stabilization of Rh(0) and Ru(0) nanoparticles allowing to obtain high conversions (>90 %) and selectivities (>98 %) with all substrates tested. Easy recovery by liquid/liquid extraction allowed to separate the catalyst from the reaction products, and recycling experiments demonstrated that MNPs-CS were highly efficiency up to three times in best hydrogenation conditions.

Lewis Acid-Mediated Friedel-Crafts-Type Formylation of Alkenes with Dichloromethyl Methyl Ether in the Presence of Pyridines

Various alkenes are formylated with dichloromethyl methyl ether (MOMCl2) by the combined use of SnCl4/2,6-dibromopyridine (B1) or AgOTf/pyridine (B4) via Friedel-Crafts-type reaction. The former reagent combination is mainly applied to α,α-diarylalkenes, while the latter one is applied not only to arylalkenes but also to some alkylalkenes. Vinyl aldehydes are exclusively obtained from alkenes that can possibly afford both allyl and vinyl aldehydes.

Photoredox/Nickel Dual Catalysis-Enabled Aryl Formylation with 2,2-Dimethoxy-N,N-dimethylethan-1-amine as CO Source

Herein, a dual photoredox/nickel catalyzed formylation of aryl bromide with commercially available 2,2-dimethoxy-N,N-dimethylethan-1-amine as an effective CO source has been successfully achieved, delivering a series of aromatic aldehydes in moderate to good yields. Compared with the traditional reductive carbonylation process, this newly designed synthetic protocol provides a straightforward toolbox to access aromatic aldehydes, obviating the use of carbon monoxide and stoichiometric reductants. Finally, the utility of this direct formylation reaction was demonstrated in the pharmaceutical analogue synthesis.

HAT-Mediated Electrochemical C(sp2)-H Acylation of Quinolines with Alcohols

Herein, an electrochemical hydrogen atom transfer (HAT) strategy for C(sp2)-H formylation of electron-deficient quinolines and isoquinolines is described. The cheap methanol acts as a formyl source with a catalytic amount of N-hydroxyphthalimide (NHPI) as the hydrogen atom transfer (HAT) catalyst. The advantages of this reaction are transition-metal-catalyst- and chemical-oxidant-free conditions, and the protocol could also be applied to the direct C(sp2)-H acetylation or propionylation of quinolines.

Gas-phase formation of Grignard-type organolanthanide (III) ions RLnCl3 - : The influences of lanthanide center and hydrocarbyl group

RATIONALE

Compared with organomagnesium compounds (Grignard reagents), the Grignard-type organolanthanides (III) exhibit several utilizable differences in reactivity. However, the fundamental understanding of Grignard-type organolanthanides (III) is still in its infancy. Decarboxylation of metal carboxylate ions is an effective method to obtain organometallic ions that are well suited for gas-phase investigation using electrospray ionization (ESI) mass spectrometry in combination with density functional theory (DFT) calculations.

METHODS

The (RCO₂ )LnCl₃ ^- (R = CH₃ , Ln = La-Lu except Pm; Ln = La, R = CH₃ CH₂ , CH₂ CH, HCC, C₆ H₅ , and C₆ H₁₁ ) precursor ions were produced in the gas phase via ESI of LnCl₃ and RCO₂ H or RCO₂ Na mixtures in methanol. Collision-induced dissociation (CID) was employed to examine whether the Grignard-type organolanthanide (III) ions RLnCl₃ ^- can be obtained via decarboxylation of lanthanide chloride carboxylate ions (RCO₂ )LnCl₃ ^- . DFT calculations can be used to determine the influences of lanthanide center and hydrocarbyl group on the formation of RLnCl₃ ^- .

RESULTS

When R = CH₃ , CID of (CH₃ CO₂ )LnCl₃ ^- (Ln = La-Lu except Pm) yielded decarboxylation products (CH₃ )LnCl₃ ^- and reduction products LnCl₃ ·^- with a variation in the relative intensity ratio of (CH₃ )LnCl₃ ^- /LnCl₃ ·^- . The trend is as follows: (CH₃ )EuCl₃ ^- /EuCl₃ ·^-  < (CH₃ )YbCl₃ ^- /YbCl₃ ·^-  ≈ (CH₃ )SmCl₃ ^- /SmCl₃ ·^-  < other (CH₃ )LnCl₃ ^- /LnCl₃ ·^- , which complies with the trend of Ln (III)/Ln (II) reduction potentials in general. When Ln = La and hydrocarbyl groups were varied as CH₃ CH₂ , CH₂ CH, HCC, C₆ H₅ , and C₆ H₁₁ , the fragmentation behaviors of these (RCO₂ )LaCl₃ ^- precursor ions were diverse. Except for (C₆ H₁₁ CO₂ )LaCl₃ ^- , the four remaining (RCO₂ )LaCl₃ ^- (R = CH₃ CH₂ , CH₂ CH, HCC, and C₆ H₅ ) ions all underwent decarboxylation to yield RLaCl₃ ^- . (CH₂ CH)LaCl₃ ^- and especially (CH₃ CH₂ )LaCl₃ ^- are prone to undergo β-hydride transfer to form LaHCl₃ ^- , whereas (HCC)LaCl₃ ^- and (C₆ H₅ )LaCl₃ ^- are not. A minor reduction product, LaCl₃ ·^- , was formed via C₆ H₅ radical loss of (C₆ H₅ )LaCl₃ ^- . The relative intensities of RLaCl₃ ^- compared to (RCO₂ )LaCl₃ ^- decrease as follows: HCC > CH₂ CH > C₆ H₅  > CH₃  > CH₃ CH₂  >> C₆ H₁₁ (not visible).

CONCLUSION

A series of Grignard-type organolanthanide (III) ions RLnCl₃ ^- (R = CH₃ , Ln = La-Lu except Pm; Ln = La, R = CH₃ CH₂ , CH₂ CH, HCC, and C₆ H₅ ) were produced from (RCO₂ )LnCl₃ ^- via CO₂ loss, whereas (C₆ H₁₁ )LaCl₃ ^- did not. The experimental and theoretical results suggest that the reduction potentials of Ln (III)/Ln (II) couples as well as the bulkiness and hybridization of hydrocarbyl groups play important roles in promoting or limiting the formation of RLnCl₃ ^- via decarboxylation of (RCO₂ )LnCl₃ ^- .

Rhodium-Catalyzed Formylation of Unactivated Alkyl Chlorides to Aldehydes

The first rhodium-catalyzed formylation of non-activated alkyl chlorides with syn gas (H₂ /CO) allows to produce aldehydes in high yields (25 examples). A catalyst optimization study revealed Rh(acac)(CO)₂ in the presence of 1,3-bisdiphenylphosphinopropane (DPPP) as the most active catalyst system for this transformation. Key for the success of the reaction is the addition of sodium iodide (NaI) to the reaction system, which leads to the formation of activated alkyl iodides as intermediates. Depending on the reaction conditions, either the linear or branched aldehydes can be preferentially obtained, which is explained by a different mechanism.

Selective carbon-phosphorus bond cleavage: expanding the toolbox for accessing bulky divalent lanthanoid sandwich complexes

The synthesis of two new tetra- and penta-phenycyclopentadienyldiphenylphosphine pro-ligands which readily undergo selective C-P bond cleavage has allowed for the facile synthesis of bulky divalent octa- and deca-phenylmetallocenes of europium, ytterbium and samarium.