A convenient, effective and mild protocol has been developed for the palladium-catalyzed ligand-free Suzuki reaction of aryl bromides with arylboronic acids in aqueous N,N-dimethylformamide (DMF) in the presence of K 2 CO 3 and a catalytic amount of PdCl 2 in air at room temperature. It is noteworthy that the volume ratio of water-DMF and base play important roles in the reaction, and various functional groups are tolerated under the optimized conditions. Furthermore, this protocol could be extended to the cross-couplings of nitrogen-based heteroaryl halides with arylboronic acids in moderate to excellent yields.

The first catalytic cascade reaction of activated isocyanides with para-quinone methide-aryl esters is presented. Catalyst-enabled divergent pathways have also been achieved to deliver skeletally diverse products. While Ag catalysis leads to an unprecedented highly diastereoselective synthesis of tricyclic ketals, a simple procedure employing Cu catalysis produces oxazole-containing triarylmethanes in high efficiency through an unexpected C-C bond cleavage.

Traditionally, domino reactions are defined as processes of two or more bond-forming reactions, in which the subsequent transformation takes place at the functionalities obtained in the former transformation under identical reaction conditions. [1,2] In linear domino reactions, the progress of the former step will always affect that of the next steps (Figure 1 a). Among the domino/cascade reactions, organocatalytic enantioselective reactions [3] have been developed at a remarkable pace after the revitalization of the field of organocatalysis. [4,5] However, we planned to develop another kind of domino reaction, which we call a "branched domino reaction" (Figure 1 b). In this domino sequence, the starting material can be used in two parallel reactions at the same time under identical conditions to generate two intermediates, which will then act as reactants in the next reaction step to form the desired product. In this version, the progress of the first step will have no effect on the second step, and higher overall yields could be achieved. This will enable the efficient synthesis of complex molecules from a few simple starting materials in an ecologically and economically manner.In 2011, Wang and co-workers [6] and Hayashi et al. [7] independently reported the diphenylprolinol trimethylsilyl ether (I) [8] catalyzed enantioselective b-functionalization of aldehydes through oxidation of enamines, formed from the amine catalyst and aldehydes, to iminium ions. In this "oxidative enamine catalysis", o-iodoxybenzoic acid (IBX) and 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ) were used as the oxidants for converting the enamines to iminium ions in the presence of the amine catalyst, which facilitated the further nucleophilic addition to afford the b-functionalized products. Shortly after, Rueping and co-workers [9] reported an enantioselective oxidative domino reaction, in which an allylic alcohol was oxidized in situ to an aldehyde by MnO 2 , followed by the tandem cyclopropanation and 1,4addition reactions with high yields and enantioselectivities. Very recently, Jang and co-workers presented a combination of a copper complex and a chiral amine for the transformation of allylic alcohols to enantiomerically enriched b-functionalized aldehydes. In this sequence, the allylic alcohols were oxidized to aldehydes followed by the formation of iminium intermediates. [10] We wondered whether both the enamine and iminium salt intermediates derived from the aldehyde and catalyst could be simultaneously applied in the same cascade reaction, which means that two parallel reactions starting from the aldehyde occur at the same time during the transformation process (Scheme 1).Herein we report the use of an aldehyde as both nucleophile and electrophile in such a branched domino reaction for the formation of six-membered-ring derivatives through oxidative enamine catalysis (Scheme 2).First, we needed to figure out whether the enamine generated from aldehyde and amine catalyst could act as nucleophile in the presence of an oxidant...

A simple and efficient protocol has been developed for the PdCl(2)-catalyzed ligand-free and aerobic Suzuki reaction of aryl bromides or nitrogen-based heteroaryl bromides with arylboronic acids in good to excellent yields in aqueous ethanol. A systematic investigation on the effect of different atmospheres on the reactivity of the palladium-catalyzed Suzuki reaction has been carried out, the results show that an aerobic atmosphere demonstrates a positive effect on the reactivity of the Suzuki reaction in an aqueous media and a negative effect in a pure organic solvent, which exhibits that the water plays a crucial role for the function of the atmosphere on the palladium-catalyzed ligand-free Suzuki reaction.