RESUMO
We here reported a highly stereoselective method for the synthesis of polysubstituted conjugated dienes from α-aryl α-diazo alkynyl ketones and pyrazole-substituted unsymmetric aminals under mild conditions, which was promoted by photo-irridation and involved with 1,6-dipolar intermediate and quadruple sigmatropic rearrangements, was successfully developed. In this transformation, the cleavage of four bonds and the recombination of five bonds were implemented in one operational step. This protocol provided a modular tool for constructing dienes from amines, pyrazoles and α-alkynyl-α-diazoketones in one-pot manner. The results of mechanistic investigation indicated that the plausible reaction path underwent the 1,6-sigmatropic rearrangement instead of the 1,5-sigmatropic rearrangement.
RESUMO
An asymmetric para-C(sp2 )-H bond functionalization of alkyl benzene derivatives was successfully developed via cooperative catalysis of gold and chiral phosphoric acid (CPA), leading to synthetically useful chiral 1,1-diaryl motifs. Chiral phosphoric acid, ligand, and molecular sieves were found to be crucial for enantioselectivity control of this transformation. The salient features of this protocol include mild conditions, high efficiency, commercially available starting materials, highly chemo- and site- as well as enantioselective aromatic C-H functionalization, broad substrate scope, and extensive applications of the chiral products. The mechanistic studies suggested that two CPAs might be involved in chiral induction.
