Preparation of a Family of 10-Hydroxybenzo[h]quinoline Analogues via a Modified Sanford Reaction and Their Excited State Intramolecular Proton Transfer Properties

Abstract

We have developed a highly optimized methodology that allows for the oxidative acetoxylation of a sterically and electronically demanding library of analogues of benzo[h]quinoline. The optimal conditions for the insertion of an OAc group were identified after examining various reaction parameters (solvent, oxidant, catalyst, temperature, time). The conditions identified (Pd(OAc)(2), PhI(OAc)(2), MeCN, 150 °C, 16 h), combined with the hydrolysis of acetates, resulted in the formation of hydroxybenzoquinolines in 27-59% yield, whereas all previously published procedures were ineffective. This synthesis was compatible with diverse functionalities (ester, aldehyde, carbon-carbon triple bond) and, most importantly, worked for sterically hindered analogues as well as for compounds possessing electron-donating and electron-withdrawing substituents at various positions. All the obtained compounds demonstrated excited-state intramolecular proton transfer (ESIPT) manifesting as small fluorescence quantum yields and large Stokes shifts (8300-9660 cm(-1)). The effect of structural variations in eight 10-hydroxybenzo[h]quinoline analogues on absorption and emission properties was studied in detail.

Deuterium Isotope Effects on 13C-NMR Chemical Shifts of 10-Hydroxybenzo[h]quinolines

“…10-Hydroxybenzo[ h ]quinolines (HBQs) display excited-state intermolecular proton transfer (ESIPT), which results in interesting photophysical properties [1,2,3,4,5,6,7,8,9,10]. ESIPT is, among others, a direct consequence of very strong intramolecular hydrogen bonding [2,3], and it has been recently studied both experimentally and theoretically.…”

Diels–Alder cycloadditions of N-arylpyrroles via aryne intermediates using diaryliodonium salts

“…To demonstrate the practical utility of this methodology, treatment of 3aa with 20 mol % TsOH·H 2 O in DCE at 80 °C resulted in N -phenylnaphthalen-1-ylamine ( 4 ) in 93% yield [ 23 ], which was widely used in dye-sensitized solar cells [ 24 ], hole transport materials [ 25 – 26 ] and organic light-emitting diodes (OLEDs, Scheme 2 ) [ 27 ]. In another similar reaction with 3am , a novel N -phenylamine derivative 5 was synthesized in 75% yield ( Scheme 2 ), whose structure was determined by 2D-NMR analyses (see Supporting Information File 1 ).…”

A Facile Synthesis of Benzo[h]quinolines via Silica‐TsOH‐P2O5 Promoted Condensation of 1‐Naphthylamines with 1,3‐Diketones under Solvent Free Conditions

“…The combined organic layer was dried over sodium sulfate and concentrated on a rotary evaporator to give a residue, which was purified on silica gel [V(PE)∶V(EA)＝10∶1, as eluent) to afford a yellow solid in 88 % yield. [8] 5, 144.8, 132.2, 131.0, 126.6, 126.4, 125.5, 125.1, 123.9, 122.0, 119.9, 119.1, 31.0, 24.4, 13.4, 12.7;IR (film) ν: 3048, 2968IR (film) ν: 3048, , 2933IR (film) ν: 3048, , 2874IR (film) ν: 3048, , 1622IR (film) ν: 3048, , 1594IR (film) ν: 3048, , 1561IR (film) ν: 3048, , 1505IR (film) ν: 3048, , 1461IR (film) ν: 3048, , 1385 81,152.97,144.71,132.1,131.3,126.5,126.3,125.5,125.0,124.1,121.6,119.7,114.7,36.1,27.5,22.1,21.8;IR (film) 6,127.7,126.4,125.2,123.9,123.6,123.3,121.0,25.2,20.2,18.9;IR (KBr) 8,144.2,132.1,130.9,126.5,125.2,124.3,122.8,121.9,119.6,119.1,31.0,…”