Ambient-Temperature Carbon–Oxygen Bond Cleavage of an α-Aryloxy Ketone with Cp2Ti(BTMSA) and Selective Protonolysis of the Resulting Ti–OR Bonds

Recent Advances in Applications of Acidophilic Fungi to Produce Chemicals

Processing of fossil fuels is the major environmental issue today. Biomass utilization for the production of chemicals presents an alternative to simple energy generation by burning. Lignocellulosic biomass (cellulose, hemicellulose and lignin) is abundant and has been used for variety of purposes. Among them, lignin polymer having phenyl-propanoid subunits linked together either through C-C bonds or ether linkages can produce chemicals. It can be depolymerized by fungi using their enzyme machinery (laccases and peroxidases). Both acetic acid and formic acid production by certain fungi contribute significantly to lignin depolymerization. Fungal natural organic acids production is thought to have many key roles in nature depending upon the type of fungi producing them. Biological conversion of lignocellulosic biomass is beneficial over physiochemical processes. Laccases, copper containing proteins oxidize a broad spectrum of inorganic as well as organic compounds but most specifically phenolic compounds by radical catalyzed mechanism. Similarly, lignin peroxidases (LiP), heme containing proteins perform a vital part in oxidizing a wide variety of aromatic compounds with H₂O₂. Lignin depolymerization yields value-added compounds, the important ones are aromatics and phenols as well as certain polymers like polyurethane and carbon fibers. Thus, this review will provide a concept that biological modifications of lignin using acidophilic fungi can generate certain value added and environmentally friendly chemicals.

Titanium coordination compounds: from discrete metal complexes to metal–organic frameworks

Recent advances in titanium based MOFs and relevant titanium molecular compounds will be discussed in this review. Particular attention will be devoted to their promising photoredox properties.

Transition-metal catalyzed valorization of lignin: the key to a sustainable carbon-neutral future

The development of a sustainable, carbon-neutral biorefinery has emerged as a prominent scientific and engineering goal of the 21st century. As petroleum has become less accessible, biomass-based carbon sources have been investigated for utility in fuel production and commodity chemical manufacturing. One underutilized biomaterial is lignin; however, its highly crosslinked and randomly polymerized composition have rendered this biopolymer recalcitrant to existing chemical processing. More recently, insight into lignin's molecular structure has reinvigorated chemists to develop catalytic methods for lignin depolymerization. This review examines the development of transition-metal catalyzed reactions and the insights shared between the homogeneous and heterogeneous catalytic systems towards the ultimate goal of valorizing lignin to produce value-added products.

Fragmentation of structural units of lignin promoted by persulfate through selective C–C cleavage under mild conditions

A high selectivity and activity for the fragmentation of β-O-4 and β-1 lignin models to high-value chemicals were achieved by using persulfate.

Lignol cleavage by Pd/C under mild conditions and without hydrogen: a role for benzylic C-H activation?

The cleavage of C-O bonds in lignin model compounds without hydrogen was developed using the commercially available Pd/C. Hydrogen donor solvents are helpful for this reaction through transfer hydrogenation, but not necessary. A redox neutral process that utilizes the internal hydrogen source for the cleavage is also possible. An initial mechanistic study indicates that the β-benzylic-H atom in the substrate plays a critical role and that the present system undergoes a process different from previous reports.