A metal-free oxidative tandem coupling of activated alkenes with carbonyl C(sp 2 )-H bonds and aryl C(sp 2 )-H bonds using TBHP is established for the synthesis of 3-(2-oxoethyl)indolin-2-ones. This method allows 1,2-difunctionalization of the C-C double bond in N-arylacrylamides by simultaneous formation of two C(sp 2 )-C(sp 3 ) bonds. Scheme 1 Oxidative tandem coupling reaction. Scheme 2 Utilization of 3-(2-oxoethyl)indolin-2-ones.
A new, efficient Cu-catalyzed intramolecular C-H oxidation/acylation method has been developed for the synthesis of substituted indoline-2,3-diones (isatins). In the presence of CuCl(2) and O(2), a variety of formyl-N-arylformamides underwent the tandem reaction to afford the corresponding indoline-2,3-diones in moderate to good yields. It is noteworthy that the reaction serves as the first example of transition-metal-catalyzed transformation for the preparation of indoline-2,3-diones.
A new, general method for the synthesis of spiro[4,5]trienones is described by the intramolecular ipso-halocyclization of 4-(p-unsubstituted-aryl)-1-alkynes. In the presence of halide electrophiles, a variety of 4-(p-unsubstituted-aryl)-1-alkynes underwent the intramolecular ipso-halocyclization with water smoothly, affording the corresponding halo-substituted spiro[4,5]trienones in moderate to good yields. The obtained spiro[4,5]trienones can be applied in constructing the azaquaternary tricyclic skeleton via Pd-catalyzed Heck reaction. Notably, the prepared spiro[4,5]trienones and azaquaternary tricycles are of importance in the areas of pharmaceuticals and agrochemicals. The mechanism of the intramolecular ipso-halocyclization reaction is also discussed according to the (18)O-labeling experiments and DFT calculations.
A novel, atom economic, and environmentally friendly method for the synthesis of 2-substituted benzothiazoles and 2-substituted naphtho[2,1-d]thiazoles from N-substituted arylamines and elemental sulfur has been developed under metal-free conditions. The reaction underwent the process of double C-S bond formation through C-H bond functionalization.
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