Most homogenous gold catalyses demand ≥0.5 mol % catalyst loading. Due to the high cost of gold, these reactions are unlikely to be applicable in medium or large scale applications. Here we disclose a novel ligand design based on the privileged biphenyl-2-phosphine framework that offers a potentially general approach to dramatically lowering catalyst loading. In this design, an amide group at the 3’ position of the ligand framework directs and promotes nucleophilic attack at the ligand gold complex-activated alkyne, which is unprecedented in homogeneous gold catalysis considering the spatial challenge of using ligand to reach antiapproaching nucleophile in a linear P-Au-alkyne centroid structure. With such a ligand, the gold(I) complex becomes highly efficient in catalyzing acid addition to alkynes, with a turnover number up to 99,000. Density functional theory calculations support the role of the amide moiety in directing the attack of carboxylic acid via hydrogen bonding.

No abstract

No abstract

No abstract

No abstract

By using Mor-DalPhos as the P,N-bidentate ligand and mesylate as the counter ion, the resulting gold(I) complex catalyzes efficient oxidative transformations of various terminal alkynes into synthetically versatile methanesulfonyloxymethyl ketones. The mild reaction conditions and high efficiency permit the one-pot synthesis of a range of valuable 2,4-disubstituted thiazoles by subjecting the resulting reaction mixture to a further condensation with thioamides under mild conditions. Keywords: carbenes; catalysis; gold; oxidation; thiazoles Aliphatic ketones with good a-leaving groups are versatile substrates for a diverse range of organic transformations. However, their schematically straightforward one-step preparations from aliphatic ketones, especially unsymmetrical linear ones, can be plagued by low or moderate regioselectivity [1] and by overreaction.[2] It is fair to state there is still a lack of a generally efficient synthesis of this important class of compounds from simple substrates.A couple of years ago we developed a strategy for generating a-oxo gold carbenes via gold-catalyzed oxidation of alkynes, [3] which circumvents the use of hazardous diazo carbonyl compounds (see Scheme 2). In one of the studies, [3f] we showed that the carbene intermediate thus generated is so electrophilic that it can abstract a chloride from the reaction solvent dichloroethane, eventually yielding an a-chloromethyl ketone (i.e., 2a-Cl, Scheme 1). Interestingly, a competing trapping of the gold carbene by the acid additive, MsOH, was a minor process, as the mesylate 2a was formed in only 5% yield. While the reaction offers a useful access to ketones with good a-leaving groups (e.g., 2a-Cl and 2a), the yields are moderate ( 70 %). Moreover, 2-chloroethyl mesylate, also an alkylating reagent, [4] was formed as a by-product in a theoretically equal amount to 2a-Cl. Consequently, one-pot strategies using in situ-generated 2a-Cl as the alkylating agent can be problematic.More recently we reported that the high electrophilicity of the in situ-generated a-oxo gold carbene could be attenuated via the formation of a tricoordinated gold center (as in A), which is enabled by a P,N-bidentate ligand (Scheme 2). [3h,i] As such, weakly nucleophilic carboxamides [3h] and carboxylic acids [3i] were capable of trapping it with good efficiency (Scheme 2). To expand the scope of trapping nucleophiles and, moreover, to provide a facile and highly efficient access to aliphatic ketones with good a-leaving groups, we turned our attention to MsOH, as its conjugate base is a good leaving group. The anticipated products, mesylated ketones (e.g., 2a), are of high synthetic value.[5] Herein, we disclose an efficient synthesis of methanesulfonyloxymethyl ketones via MsOH trapping of in-situ generated a-oxo gold car- These are not the final page numbers! ÞÞ COMMUNICATIONS

No abstract

A series of transition metal sulphonato-Schiff base complexes were intercalated into Mg-Al layered-double hydroxides (LDHs). The obtained catalysts were characterized by FTIR, XRD, N 2 sorption, SEM and elemental analysis, and then were used in the selective oxidation of glycerol (GLY) using 3% H 2 O 2 as an oxidant. It was found that their catalytic performances were closely related to the loading of active complexes, the Schiff base ligands and the metal centers of the catalysts, as well as the reaction conditions. The optimal conversion of GLY was 85.0%, while the selectivity of 1,3-dihydroxyacetone (DHA) was 56.5%. Moreover, the catalysts could be reused at least 10 times.