Gold(I)-Catalyzed Synthesis of 1,5-Benzodiazepines Directly from <i>o</i>‑Phenylenediamines and Alkynes

A unique gold­(I)-catalyzed highly atom-economic synthesis of 1,5-benzodiazepines directly from <i>o</i>-phenylenediamines and alkynes has been achieved for the first time

Gold-Catalyzed Simultaneous Formation of C–C, CO, and C–F bonds in the Presence of Selectfluor: A Synthesis of Fluoroindenes from Allene Esters

An approach for the synthesis of fluorinated indene derivatives has been developed via a gold-catalyzed three-component tandem reaction between allene esters, Selectfluor, and water

Multifold Bond Cleavage and Formation between MeOH and Quinoxalines (or Benzothiazoles): Synthesis of Carbaldehyde Dimethyl Acetals

A K₂S₂O₈-mediated direct cross-coupling of quinoxalines (or benzothiazoles) with methanol leading to 2-quinoxalinyl (or 2-benzothiazolyl) carbaldehyde dimethyl acetals has been achieved. 2-Quinoxalinyl carbaldehyde dimethyl acetals were readily converted into 2-quinoxalinyl carbaldehydes in good to excellent yields under acidic conditions. Preliminary mechanistic studies suggest that the reaction proceeds via multifold bond cleavage and formation between methanol and <i>N</i>-heterocycles involving a dioxygen-participated radical process. This method allows for the synthesis of a variety of 2-quinoxalinyl (or 2-benzothiazolyl) carbaldehyde dimethyl acetals directly via cross-coupling of simple <i>N</i>-heterocyclic C–H bond and methanol under aldehyde-, acid-, and transition-metal-free conditions

Multiscale Dynamic Growth and Energy Transport of Droplets during Condensation

Condensation is an important physical process and has direct relevance for a range of engineering applications, including heat transfer, antifrosting, and self-cleaning. Understanding the mechanism of droplet growth during condensation is an important aspect, but past works have not typically considered the dynamics of the multiscale process. In this paper, we developed a dynamic growth model, which considers the continuous and multiscale nature of the droplet growth process from several nanometers to hundreds of microns. This model couples the transient phase change heat transfer and two-phase flow both inside and outside the droplet. Accordingly, the energy transport is distinct from the classical pure conduction model. We show that convection near the liquid–vapor interface and inside the droplets plays an increasingly important role as droplets grow and finally dominates the energy transport process. Driven by strong convection, the droplets mix well and the discrete layers of temperature observed in the pure conduction model disappear at the microscale. This model that considers convection can lead to over 4 times higher predicted overall heat transfer than that obtained with the pure conduction model. The interfacial mass flow through the liquid–vapor interface is the dominant factor responsible for the strong convection. We studied the critical radius where convection starts to have a significant influence on droplet growth under different subcooling temperatures and contact angles. Droplets have smaller critical radii under larger subcooling temperatures or larger contact angles, ranging from 0.5 to 20 μm. This work identifies the modes of energy transport in condensation at different scales, which not only enhances our fundamental understanding of individual droplet growth but provides design guidelines for various dropwise and jumping-droplet condensation research

Copper-Catalyzed Oxidative Cyclization of 1,5-Enynes with Concomitant C–C Bond Cleavage: An Unexpected Access to 3‑Formyl-1-indenone Derivatives

A Cu(0)/Selectfluor system-mediated oxidative cyclization of 1,5-enynes with concomitant C–C bond cleavage to access 3-formyl-1-indenone derivatives is described. Preliminary mechanistic investigations disclosed that the C–C bond cleavage involved a novel water-participated oxygen-insertion β-carbon elimination through double oxycuprations

Successive Waste as Reagent: Two More Steps Forward in a Pinnick Oxidation

The successful development of the classical Pinnick oxidation into a new and promising oxidative lactonization reaction is reported. Chiral 3-oxindolepropionic aldehydes, Michael adducts of 3-olefinic oxindoles with aliphatic aldehydes, are directly converted to spirocyclic oxindole-γ-lactones solely by sodium chlorite via a tandem Pinnick oxidation/chlorination/substitution sequence. This reaction uses waste ClO^– generated in the initial Pinnick oxidation as an ecofriendly halogenating agent for the subsequent chlorination, and then it utilizes the byproduct OH^– formed in the chlorination to facilitate the final internal substitution