Eight-membered-ring diaminocarbenes bearing naphthalene moiety in the backbone: DFT studies, synthesis of amidinium salts, generation of free carbene, metal complexes, and solvent-free copper catalyzed azide–alkyne cycloaddition (CuAAC) reaction

Abstract

A new type of eight-membered ring N-heterocyclic carbene (NHC) bearing a rigid naphthalene moiety in the backbone is reported for the first time. Stereoelectronic properties of 4,5-dihydro-1H-naphtho[1,8-ef][1,3]diazocin-3(2H)-ylidene (NaphtDHD) and smaller ring NHCs were theoretically studied at the DFT level. Amidinium salts were prepared from corresponding amidines and dibromides. Free carbene NaphtDHD-Dipp (Dipp = 2,6-diisopropylphenyl) was generated in solution by treatment of the corresponding salt with LiHMDS. It is stable in solution at low temperatures, while decomposing rapidly at room temperature. Silver(i) and copper(i) complexes were synthesized and structurally characterized in the solid state. The copper(i) complex [(NaphtDHD-Mes)CuBr] (Mes = mesityl, 2,4,6-trimethylphenyl) exhibits high catalytic activity in alkyne-azide cycloaddition (CuAAC) reaction under solvent-free conditions.

Direct Arylations via C–H Bond Functionalization of 1,2,3‐Triazoles by a Reusable Pd/C Catalyst Under Solvent‐Free Conditions

“…4‐Hexyl‐1‐( p ‐tolyl)‐1 H ‐1,2,3‐triazole (1d) :, Compound 1d was synthesized from p ‐tolylboronic acid (408 mg, 3 mmol), NaN 3 (234 mg, 3.6 mmol) and 1‐octyne (364 mg, 3.3 mmol) in accordance with a literature procedure (201 mg, 28 % yield) . Spectroscopic data are in agreement with those previously reported in the literature …”

Ring‐Expanded N‐Heterocyclic Carbenes for Copper‐Mediated Azide–Alkyne Click Cycloaddition Reactions

“…However,o nly 2o ut of 10 cycloadditions gave conversions above 10 %u nder the reported conditions. [18] Still, RE NHCs are known to improvet he catalytic efficiency in important transformations such as cross-coupling, [19] or allylic boronation [20] reactions, as well as allowing the study of elusive species( that is, three-coordinatedn ickel(I) complexes, [21] or copper(I)-hydrides [22] ). Herein we report the remarkable catalytic activity of several [CuX( RE NHC)] complexes in the formation of triazoles under click-suitable conditions.…”

Alkynyl‐ or Azido‐Functionalized 1,2,3‐Triazoles: Selective MonoCuAAC Promoted by Physical Factors

“…In both cases (solvent‐based and neat approaches), the CuAAC reaction is efficiently catalyzed by N‐heterocyclic carbene (NHC) copper(I) complexes. We selected the most catalytically active (NHC)CuX complexes under solvent‐free or apolar conditions: SIMesCuBr ( 1 a ), (6‐Mes)CuBr ( 1 b ), (7‐Mes)CuBr ( 1 c ), abnormal NHC complex (aNHC)CuCl ( 1 d ), (Naph‐8‐Mes)CuBr ( 1 e ) and well‐soluble in apolar media fluorinated (F‐NHC)CuCl ( 1 f) and tested them in the model reaction between phenylacetylene and p ‐tolylazide under following conditions: 1) heptane, 40 °C, 2) neat, 40 °C (Scheme ). The choice of reaction temperature is motivated by the fact that even daily fluctuations in temperature can alter the solubility of the reaction components leading to reproducibility issues; therefore, the temperature slightly higher than RT was chosen.…”