SnO2‐based catalysts modified by La, Ce, and Y with a Sn/Ln (Ln=La, Ce, Y) atomic ratio of 2:1 were prepared by using a co‐precipitation method and used for CO and CH4 oxidation. The catalysts were characterized by N2 adsorption–desorption, XRD, energy dispersive X‐ray spectroscopy (EDS)‐SEM, H2 temperature‐programmed reduction (TPR), X‐ray photoelectron spectroscopy (XPS), and thermogravimetric analysis differential scanning calorimetry (TGA‐DSC) techniques. All three rare earth metal oxides were found to improve the thermal stability of SnO2, which resulted in catalysts with much higher surface areas and smaller crystallite and particle sizes. However, only the addition of Ce resulted in a catalyst with improved activity for both CO and CH4 oxidation. In contrast, La and Y modification resulted in samples with decreased activity for both reactions. For the Ce‐modified sample, Ce cations were found to dope into the lattice of rutile SnO2 to form a solid‐solution structure. As a lattice impurity, ceria, the well‐known oxygen storage component (OSC), led to the formation of more defects in the matrix of SnO2 and impeded the crystallization process, which resulted in a catalyst with a higher surface area and more active oxygen species. In contrast, XRD proved that the addition of La and Y mainly led to the formation of more stable and inert pyrochlore compounds, Sn2La2O7 and Sn2Y2O7, which disrupted a major part of the active sites based on SnO2. Consequently, the oxidation activity was impaired, although these two samples also have higher surface areas than pure SnO2. The Ce‐modified sample showed not only high activity but also good reaction durability and thermal stability. Furthermore, Sn‐Ce binary oxide is a better support than SnO2, CeO2, and traditional Al2O3 supports for Pd, which gives it the potential to be applied in some real after‐treatment applications.

The merger of photoredox and transition-metal catalysis has evolved as a robust platform in organic synthesis over the past decade. The stereoselective 1,4-functionalization of 1,3-enynes, a prevalent synthon in synthetic chemistry, could afford valuable chiral allene derivatives. However, tremendous efforts have been focused on the ionic reaction pathway. The radical-involved asymmetric 1,4-functionalization of 1,3-enynes remains a prominent challenge. Herein, we describe the asymmetric three-component 1,4-dialkylation of 1,3-enynes via dual photoredox and chromium catalysis to provide chiral allenols. This method features readily available starting materials, broad substrate scope, good functional group compatibility, high regioselectivity, and simultaneous control of axial and central chiralities. Mechanistic studies suggest that this reaction proceeds through a radical-involved redox-neutral pathway.

α-Allenol is a versatile synthon in organic synthesis. The catalytic asymmetric synthesis of α-allenols from readily available starting materials remains a prominent challenge, especially when simultaneous control over axial and central chirality is required. Herein, we describe the Cr-catalyzed enantioconvergent allenylation of aldehydes with racemic propargyl halides to rapidly access a wide range of chiral αallenols with adjacent axial and central chiralities. This method features excellent regio-, diastereo-and enantioselectivity control with broad substrate scope, and provides facile access to all four stereoisomers when allied with a Mitsunobu reaction. Preliminary mechanistic studies support radicalbased reaction pathways. The synthetic utility is demonstrated by the application in late-stage functionalization and the formal total synthesis of (+)-varitriol.

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α-Allenol is a versatile synthon in organic synthesis. The catalytic asymmetric synthesis of α-allenols from readily available starting materials remains a prominent challenge, especially when simultaneous control over axial and central chirality is required. Herein, we describe the Cr-catalyzed enantioconvergent allenylation of aldehydes with racemic propargyl halides to rapidly access a wide range of chiral αallenols with adjacent axial and central chiralities. This method features excellent regio-, diastereo-and enantioselectivity control with broad substrate scope, and provides facile access to all four stereoisomers when allied with a Mitsunobu reaction. Preliminary mechanistic studies support radicalbased reaction pathways. The synthetic utility is demonstrated by the application in late-stage functionalization and the formal total synthesis of (+)-varitriol.