Regioselective ethoxy-carbonylation of indoles and indazoles using DEAD and tetraethylammonium cyanide

Probing elemental speciation in hydrochar produced from hydrothermal liquefaction of anaerobic digestates using quantitative X-ray diffraction

“…66 The reactivity of phenylhydrazine with α-dicarbonyl/α-hydroxycarbonyl and pyruvic acid via Fischer indolization mechanism were enhanced under acidic conditions to afford 2,3,4-trimethyl-1 H -indole (C39) and 1 H -indole-2-carboxylic acid (C38), respectively. 67 The former may further experience regioselective ethoxy-carbonylation with diethylazodicarboxylate, 68 ethylenation, and finally ring closure involving the ethylene group and the aldehyde and –COOH groups of 6-nitrosalicylaldehyde (C41) to precipitate as ethyl-1′,3′,3′-trimethyl-8-nitrospiro[chromene-2,2′-indoline]-5′-carboxylate. 69 The latter may couple with 3,5-dinitrobenzoic acid from nitration of benzoic acid and precipitated as indole-2-carboxylic acid·3,5-dinitrobenzoic acid (C34).…”

Direct access to carbamates via acylation of arylamines with dialkyl azodicarboxylates under metal-free conditions

“…1 H NMR (400 MHz, CDCl 3 ): δ 9.92 (s, 1H), 8.39 (dd, J = 9.2, 4.9 Hz, 1H), 7.74-7.69 (m, 2H), 7.62 (t, J = 7.4 Hz, 1H), 7.50 (t, J = 7.7 Hz, 2H), 7.34-7.26 (m, 1H), 7.22 (dd, J = 8.9, 3.0 Hz, 1H), 4.22 (q, J = 7.1 Hz, 2H), 1.31 (t, J = 7.1 Hz, 3H). 13…”

“…8 However, only a few examples have been disclosed with dialkyl azodicarboxylates as esterification reagents (Scheme 1b). [9][10][11][12][13][14][15] In 2008, Yu and co-workers reported the first Pd-catalyzed protocol for ortho-selective ethoxycarbonylation of aromatic C-H bonds using diethyl azodicarboxylate (DEAD) as an esterification reagent. 9 From the viewpoint of mechanism, a radical pathway was proposed and an ethoxyacyl radical was generated in situ through thermal decomposition of DEAD at 100 °C.…”

“…12 Despite these elegant achievements on C-H bond esterification with dialkyl azodicarboxylates, only a few studies report on X-H (X = N or O) esterification with dialkyl azodicarboxylates as acylation reagents. [13][14][15] In 2013, Lalitha and co-workers reported an elegant method for the direct carbonylation of indoles with DEAD in the presence of tetraethyl ammonium cyanide (TEACN). 13 Three years later, Guan's group successfully developed an ingenious Cu-catalyzed carbonylation between various anilines and diisopropyl azodicarboxylate (DIAD).…”

“…[13][14][15] In 2013, Lalitha and co-workers reported an elegant method for the direct carbonylation of indoles with DEAD in the presence of tetraethyl ammonium cyanide (TEACN). 13 Three years later, Guan's group successfully developed an ingenious Cu-catalyzed carbonylation between various anilines and diisopropyl azodicarboxylate (DIAD). 14 Moreover, Girard 15a and Guan 15b have independently reported O-H bond esterification to construct carbonates with dialkyl azodicarboxylates as the carbon source.…”