Decarboxylative Sulfonylation of Carboxylic Acids under Mild Photomediated Iron Catalysis.

Organic sulfones are an important class of chemical compounds widely used in many research fields. The direct decarboxylative sulfonylation of carboxylic acids is attractive but challenging, particularly when iron is used as a metal catalyst. Herein, we describe a photoinduced iron-catalytic method for the synthesis of sulfones directly using carboxylic acids via a radical-based decarboxylation. This protocol is mild, highly efficient, and easy-to-operate. A broad scope of carboxylic acids and carbon electrophiles could be well tolerated. A mechanism involving the iron-catalyzed decarboxylation, radical transfer, single-electron reduction, and nucleophilic attack is proposed.

Iron-Catalyzed Csp2-Csp3 Cross-Coupling via Double Decarboxylation: One Step Synthesis of Remote Polar Alkenes.

Herein, we report an efficient photoinduced iron-catalyzed strategy for cross-couplings of alkyl carboxylic and acrylic acids, which provides a powerful tool for the synthesis of a variety of alkenes with polar functional groups. This novel synthetic methodology can also be applied to the preparation of ketones by using α-keto acids. Mechanistic experiments revealed preliminary mechanistic details. Diverse functionalization could be achieved, which may help streamline the synthesis of complex analogues for drug discovery.

BsLPMO10A from Bacillus subtilis boosts the depolymerization of diverse polysaccharides linked via ß-1,4-glycosidic bonds.

Lytic polysaccharide monooxygenase (LPMO) is known as an oxidatively cleaving enzyme in recalcitrant polysaccharide deconstruction. Herein, we report a novel AA10 LPMO derived from Bacillus subtilis (BsLPMO10A). A substrate specificity study revealed that the enzyme exhibited an extensive active-substrate spectrum, particularly for polysaccharides linked via ß-1,4 glycosidic bonds, such as ß-(Man1 â†’ 4Man), ß-(Glc1 â†’ 4Glc) and ß-(Xyl1 â†’ 4Xyl). HPAEC-PAD and MALDI-TOF-MS analyses indicated that BsLPMO10A dominantly liberated native oligosaccharides with a degree of polymerization (DP) of 3-6 and C1-oxidized oligosaccharides ranging from DP3ox to DP6ox from mixed linkage glucans and beechwood xylan. Due to its synergistic action with a variety of glycoside hydrolases, including glucanase IDSGLUC5-38, xylanase TfXYN11-1, cellulase IDSGLUC5-11 and chitinase BtCHI18-1, BsLPMO10A dramatically accelerated glucan, xylan, cellulose and chitin saccharification. After co-reaction for 72 h, the reducing sugars in Icelandic moss lichenan, beechwood xylan, phosphoric acid swollen cellulose and chitin yielded 3176 ± 97, 7436 ± 165, 649 ± 44, and 2604 ± 130 µmol/L, which were 1.47-, 1.56-, 1.44- and 1.25-fold higher than those in the GHs alone groups, respectively (P < 0.001). In addition, the synergy of BsLPMO10A and GHs was further validated by the degradation of natural feedstuffs, the co-operation of BsLPMO10A and GHs released 3266 ± 182 and 1725 ± 107 µmol/L of reducing sugars from Oryza sativa L. and Arachis hypogaea L. straws, respectively, which were significantly higher than those produced by GHs alone (P < 0.001). Furthermore, BsLPMO10A also accelerated the liberation of reducing sugars from Celluclast® 1.5 L, a commercial cellulase cocktail, on filter paper, A. hypogaea L. and O. sativa L. straws by 49.58 % (P < 0.05), 72.19 % (P < 0.001) and 54.36 % (P < 0.05), respectively. This work has characterized BsLPMO10A with a broad active-substrate scope, providing a promising candidate for lignocellulosic biomass biorefinery.

Metal-free C8-H functionalization of quinoline N-oxides with ynamides.

The metal-free C8-H functionalization of quinoline N-oxides with ynamides is unveiled for the first time by the intramolecular Friedel-Crafts-type reaction of quinolyl enolonium intermediates generated from Brønsted acid-catalyzed addition of quinoline N-oxides to ynamides. Various quinoline N-oxides and terminal ynamides prove to be suitable substrates for this method. A one-pot protocol was then developed for the metal-free direct C8-H functionalization of quinolines.

A Hg(OTf)2-Catalyzed Enolate Umpolung Reaction Enables the Synthesis of Coumaran-3-ones and Indolin-3-ones.

The potential of mercury catalysis has been extended to the arena of enolate umpolung reactions for the first time by the generation of enolonium species via Hg(OTf)2-catalyzed N-oxide addition to alkynes. The enolonium species formed can undergo intramolecular nucleophilic attack by hydroxyl or amino groups, leading to the synthesis of various coumaran-3-ones and indolin-3-ones.

Facile synthesis of 2-substituted benzo[b]furans and indoles by copper-catalyzed intramolecular cyclization of 2-alkynyl phenols and tosylanilines.

A catalytic amount of CuCl and Cs2CO3 was employed to synthesize a variety of 2-substituted benzo[b]furans and indoles by an intramolecular cyclization of 2-alkynyl phenols and tosylanilines. This protocol features mild conditions, high yields and broad substrate scope, which makes it a practical method for the synthesis of 2-substituted benzo[b]furans and indoles.

Broad scope gold(i)-catalysed polyenyne cyclisations for the formation of up to four carbon-carbon bonds.

The polycyclisation of polyenynes catalyzed by gold(i) has been extended for the first time to the simultaneous formation of up to four carbon-carbon bonds, leading to steroid-like molecules with high stereoselectivity in a single step with low catalyst loadings. In addition to terminal alkynes, bromoalkynes can also be used as initiators of polyene cyclisations, giving rise to synthetically useful cyclic bromoalkenes.

Formal (4+1) cycloaddition of methylenecyclopropanes with 7-aryl-1,3,5-cycloheptatrienes by triple gold(I) catalysis.

7-Aryl-1,3,5-cycloheptatrienes react intermolecularly with methylenecyclopropanes in a triple gold(I)-catalyzed reaction to form cyclopentenes. The same formal (4+1) cycloaddition occurs with cyclobutenes. Other precursors of gold(I) carbenes can also be used as the C1 component of the cycloaddition.