Electrochemical Difunctionalization of Styrenes via Chemoselective Oxo-Azidation or Oxo-Hydroxyphthalimidation

Abstract

Atom- and step-economic oxo-azidation and oxo-hydroxyphthalimidation of styrenes have been developed under mild electrolytic conditions, respectively. Various valuable alpha-azido or hydroxyphthalimide aromatic ketones were synthesized efficiently from readily available styrenes, azides, and N-hydroxyphthalimides. Mechanism studies show that two different pathways involved in these two transformations.

Electrochemical vicinal oxyazidation of α-arylvinyl acetates

“…Based on our reaction results and the known literature [13,14], a possible mechanism is proposed (Scheme 4). The enol acetate A first undergoes anodic oxidation to form a radical cation intermediate B, which is then intercepted by azidotrimethylsilane to afford the benzyl radical C. Subsequently, this radical is further anodically oxidized to its oxocarbenium ion intermediate D, which finally reacts with water to form the desired product E. According to our 18 O labeling experiment, the oxygen source of the newly installed carbonyl group probably originates from the vinyl acetate, not from H 2 O.…”

“…The relatively low yield of the isopropyl-substituted one (7) was attributed to the competing oxidation of the isopropylbenzene moiety [31,36], which was consistent with its relative low oxidation potential (E onset = 1.68 V vs Fc +/0 ). Other electrondonating substituents, such as the OMe (10-12), OPh (13), and OAc (14) were also well tolerated.…”

“…Retrosynthetically, the nucleophilic substitution of α-bromoketones by sodium azide [ 10 ] and oxidation of the azido alcohols [ 11 ] are among the most straightforward methods to generate azidoketones. Remarkably, photoredox [ 12 ] and electrochemical [ 13 ] oxyazidation of vinylarenes are also becoming competent synthetic approaches. Besides vinylarenes, vinyl acetates are potentially versatile precursors for the anticipated vicinal oxyazidation.…”

Na2S-Mediated One-Pot Selective Deoxygenation of α-Hydroxyl Carbonyl Compounds including Natural Products

“…The process requires the functionalization of phenylacetic acid to phenylacetyl chloride by stoichiometric PCl 3 or SOCl 2 prior to the C–C bond coupling [ 8 , 9 , 10 , 11 , 12 ]. Other elegant strategies, including hydration [ 13 ], olefin cleavage [ 14 ], benzylic oxidation [ 15 ] and C–O bond breaking protocols [ 16 , 17 , 18 ], have also been developed to access DOBs in recent years ( Scheme 1 ). However, these methods generally required the prefunctionalization of starting molecules or, alternatively, the use of expensive substrates [ 13 , 14 , 15 , 16 ].…”

“…Other elegant strategies, including hydration [ 13 ], olefin cleavage [ 14 ], benzylic oxidation [ 15 ] and C–O bond breaking protocols [ 16 , 17 , 18 ], have also been developed to access DOBs in recent years ( Scheme 1 ). However, these methods generally required the prefunctionalization of starting molecules or, alternatively, the use of expensive substrates [ 13 , 14 , 15 , 16 ]. Thus, it is highly desirable to develop practical processes for DOB production using cheap and easy-to-handle feedstocks.…”