Amidation of 1,3-Diarylallylic Compounds Catalysed by 2,3-Dichloro-5,6-Dicyano-1,4-Benzoquinone with Molecular Oxygen as the Terminal Oxidant

Abstract

Oxidative coupling reactions play an important role in organic chemistry. With the concept of green chemistry, 1 the use of molecular oxygen as the terminal oxidant in an oxidation reaction has attracted much attention owing to its great abundance in nature and water as the only by-product. To accomplish the oxidation, a transition metal or transition-metal complex is usually required to activate the molecular oxygen. [2][3][4] Recently, there has been a great deal of emphasis on metalfree reactions in organic synthesis because metal residues can pollute the pharmaceutical intermediates and target products. To the best of our knowledge, few efforts have been reported involving metal-free oxidative couplings which simultaneously employ molecular oxygen as the terminal oxidant.Formation of C-N bonds is an important fundamental reaction in organic synthesis because many bioactive and medicinal molecules are nitrogen-containing compounds. [5][6][7] Allylic amination represents one of the most common C-N bond formation methodologies. An efficient and atom economical approach to allylic amination is to use directly allylic alcohols as electrophiles with catalysts such as transitionmetal complexes or salts and Lewis or Brønsted acids. [8][9][10][11][12][13][14][15][16][17] Despite the excellent progress which has been made, it would obviously be attractive if allylic amination might be achieved via C-H oxidative activation. Recently, our group has reported the metal-free coupling between 1,3-diarylpropenes and nitrogen nucleophiles promoted by a stoichiometric amount of 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ). 18 However, the use of a stoichiometric amount of DDQ caused purification difficulties because of the formation of the by-product DDQH 2 . With an interest in developing an application using a catalytic amount of DDQ in the oxidative reaction, 19 we wish to report an efficient amidation at a diarylallylic sp 3 carbon hydrogen centre catalysed by DDQ with molecular oxygen as the terminal oxidant.

A Simple Synthesis of 1,3-Diphenylpropene

“…Vasilyeva, V.V. Zorin, 2018, published in Zhurnal Obshchei Khimii, 2018 1,3-Diphenylpropene isomers are used in organic synthesis as the starting substrates and model compounds [1][2][3][4]. The specific reactivity of 1,3-diphenylpropene is due to the presence of methylene group, being simultaneously in the allyl and benzyl positions.…”