Visible‐Light‐Promoted Reaction ofN‐Hydroxyphthalimide Esters with Vinyl Boronic Pinacol Ester

Abstract

A novel and easy-to-execute light-driven protocol for the preparation of alkyl boronic acid pinacol esters from vinyl boronate using N-hydroxyphthalimide esters as the potential precursor is described. In this photochemical protocol, the Nhydroxyphthalimide ester's fragmentation generates C-centered radicals, which undergo a radical Michael addition to vinyl boronic pinacol ester furnishing the desired products. A good substrate scope having various functionalities is presented and good to high yields are obtained.

Visible photons as ideal reagents for the activation of coloured organic compounds

“…356 However, these arenes are recently becoming interesting substrates for the photogeneration of nitrenes by tuning the right reaction conditions. 224,225 Moreover, due to the recent development of visible LEDs technology it is possible to carry out reactions on coloured compounds, previously promoted by multichromatic sources which mostly emit in the UV region. The easy accessibility to these sources allowed for the discovery of new processes on known chromophores.…”

“…223 Recently, there has been an increased interest in the photochemistry of nitroarenes. 224 As a matter of fact, aryl nitrenes were also obtained through the visible-light photolysis of nitroaromatics (e.g., 69.1, Scheme 69). Thus, the excited 69.1 underwent deoxygenation with P(OiPr) 3 to form nitrene 69.4 and the corresponding aminoazepine from it.…”

“…Recently, there has been an increased interest in the photochemistry of nitroarenes. 224 As a matter of fact, aryl nitrenes were also obtained through the visible-light photolysis of nitroaromatics ( e.g. , 69.1 , Scheme 69).…”

Borylated Cyclopentanes via Atom Transfer Radical [3+2] Annulation

“…[42] Nucleophilic radicals also add efficiently to vinylboronic esters as demonstrated by Carboni. [43] Similarly, hydroalkylation involving either hydrogen atom transfer (HAT) from Hantzsch esters [44,45] or reductive [46][47][48][49] and oxidative [50,51] termination processes have been reported. For instance, Aggarwal reported the addition of nucleophilic α-aminoalkyl radicals generated under photoredox conditions from the corresponding αaminoacids to vinylboronic esters.…”

Visible light-induced metal-free cascade denitrogenative borylation and iodination of nitroarenes

“…13,14 The active triplet excited state of nitroarenes could be formed through n → π* excitation with the irradiation of light, which has the potential to act as hydrogen atom transfer (HAT) reagents, EDA complex partners, or ligands for LMCT in metal-catalyzed reactions. [15][16][17][18][19][20][21] Although different reagents have been employed to couple with nitroarenes for diverse transformations, the use of B 2 pin 2 or I 2 as borylation and iodination reagents to react with nitroarenes under visible light for accessing arylboronates and iodobenzenes has not been explored thus far.…”