Yu-Feng Liu

Transition-Metal-Free TBAI-Facilitated Addition-Cyclization of N-Methyl-N-arylacrylamides with Arylaldehydes or Benzenesulfonohydrazides: Access to Carbonyl- and Sulfone-Containing N-Methyloxindoles.

A highly efficient addition-cyclization of N-methyl-N-arylacrylamides with arylaldehydes or benzenesulfonohydrazides was developed using a catalytic amount of the quaternary ammonium salt (TBAI) under metal-free conditions, leading to the carbonyl- and sulfone-containing oxindoles. Compared to previous methods, which require excessive amounts of explosive organic peroxides and precious or toxic metal reagents, the present protocol, which gave access to 3,3-disubstituted oxindoles, is a safe and green approach, resulting in the formation of various useful carbonyl- and sulfone-containing oxindoles in yields of 40-94%.

Transition-Metal-Free Synthesis of Carbonyl-Containing Oxindoles from N-Arylacrylamides and α-Diketones via TBHP- or Oxone-Mediated Oxidative Cleavage of C(sp(2))-C(sp(2)) Bonds.

Carbonyl-containing oxindoles can be prepared from N-arylacrylamides and α-diketones by TBHP- or oxone (KHSO5)-mediated C(sp(2))-C(sp(2)) bond cleavage and new C(sp(2))-C(sp(3)) bond formation. This methodology is characterized by its simple and transition-metal-free conditions and good functional group compatibility utilizing inexpensive and readily available reagents, thus providing a practical and efficient approach to an important class of 3-(2-oxoethyl)indolin-2-ones which are highly valued synthetic intermediates of biologically active molecules. In this transformation, alkylcarbonyl-containing oxindoles were obtained in majority when N-arylacrylamides reacted with asymmetric aliphatic/aromatic α-diketones. On the basis of the preliminary experiments, a plausible mechanism of this transformation is disclosed.

Transition Metal-Free α-Csp3-H Methylenation of Ketones to Form C═C Bond Using Dimethyl Sulfoxide as Carbon Source

A direct α-Csp3-H methylenation of arylketones to form C═C bond using dimethyl sulfoxide as one-carbon source is achieved under transition metal-free reaction condition. Various aryl ketone derivatives react readily with DMSO, producing the α,β-unsaturated carbonyl compounds in yields of 42 to 90%. This method features a transition metal-free reaction condition, wide substrate scope and using DMSO as novel one-carbon source to form C═C bond, thus providing an efficient and expeditious approach to an important class of α,β-unsaturated carbonyl compounds. Based on the preliminary experiments, a plausible mechanism of this transformation is disclosed.

Transition-Metal-Free Oxidative Decarboxylative Cross Coupling of α,β-Unsaturated Carboxylic Acids with Cyclic Ethers under Air Conditions: Mild Synthesis of α-Oxyalkyl Ketones

A novel K2S2O8-promoted decarboxylative cross coupling of α,β-unsaturated carboxylic acids with cyclic ethers was developed under aerobic conditions. The present protocol, which includes C-C and C═O bond formation in one step through addition, oxidation, and decarboxylation processes, leads to the desired ketone products in moderate to excellent yields. In addition, mechanism studies showed that the transformation process undergoes a radical pathway via a direct activation of the α-sp3 C-H bond of oxygen of the cyclic ether.