Terminal Organylchalcogenoethyl- and -propylamines and Their Schiff Base Derivatives

Abstract

A series of organoselanyl-and organotellanyl-substituted ethyl-and propylamines and their hydrochlorides, as well as 2-(methylsulfanyl)ethylamine have been synthesized. Efficient general synthetic routes have been developed to chalcogen(S, Se, Te)-containing Schiff bases with di-and trimethylene bridges between the nitrogen atom of the imino group and the chalcogen, by condensation of 3-(tert-butyl)-and 3-(1-ethylpropyl)-2-hydoxybenzenecarbaldehydes with the amines. The influence of the organylchalcogenyl-group on some spectral characteristics ( 1 H, 13 C, 77 Se NMR spectroscopy) of both amines and Schiff bases is discussed.Schiff bases are among the most investigated ligands in coordination chemistry, 1 but interest in them remains high, due partly to the wide range of possibilities for varying the substituents in these ligand systems and also because of their potential applications in homogeneous catalysis. One class of Schiff bases, which has received particular attention, is that of the bidentate salicylaldimines formed by the reaction of o-hydroxybenzaldehydes with the corresponding amines. Use of amines which incorporate alkylamino-, hydroxy-, alkoxy-, alkyl-and arylthio groups capable of additional coordination leads to the possibility of an increase in denticity of the ligand in complex formation. 2 An alternative procedure for the preparation of this type of ligands containing sulfur consists of electrochemical rupture of the disulfide bond of the corresponding bis-2-salicylaldiminoethyl disulfides. 3 Large 24-and 28-membered macrocyclic Schiff bases are also known with selenide and telluride functions linked to the nitrogen atom of the imine bond through polymethylene bridges (CH 2 ) n (n = 2,3). 4 Schiff bases bearing a sulfide group connected to the nitrogen atom of the imine function by a dimethylene bridge are formed by condensation of 2-(organosulfanyl)ethylamine, 2-[(2-aminoethyl)thiomethyl]benzimidazole or imidazole, with substituted salicylaldehydes, 5 acetophenone or acetylacetones. 6Taking into account the potential of these Schiff bases as tridentate ligands, 1 and at the same time the extremely scarce knowledge about these compounds, which is limited mainly to sulfur-containing derivatives, we have synthesized salicylaldimines bearing sulfide-, selenide-and telluride functions connected to nitrogen by a polymethylene bridge (CH 2 ) n (n = 2,3) starting from 3-(tert-butyl)-and 3-(1-ethylpropyl)-2-hydroxybenzenecarbaldehydes and a series of 2-(organylselanyl)ethylamines 6, 2-(organyltellanyl)ethylamines 7, 3-(organylselanyl)propylamines 8, and 3-(organyltellanyl)propylamines 9 synthesized by us. For comparison purposes we have also prepared the analogous Schiff bases using 2-(methylsulfanyl)ethylamine 5.It should be pointed out that terminal organylchalcogenylalkylamines in themselves are prospective ligands, which has been shown for N-{2-(4-methoxyphenyltellanyl)ethyl}morpholine, 7 bis-{2-(N-morpholino)ethyl}telluride, 7b 3-organylselanyl(tellanyl) propylamines, 8 2-organylselanylethylamine, ...

New Palladium Complexes with S‐ or Se‐Containing Schiff‐Base Ligands as Efficient Catalysts for the Suzuki–Miyaura Cross‐Coupling Reaction of Aryl Bromides with Phenylboronic Acid under Aerobic Conditions

“…The synthesis of the palladium complexes 3a – d is outlined in Scheme . Chalcogen‐containing Schiff bases 2‐(1‐ethylpropyl)‐6‐({[2‐(methylsulfanyl)ethyl]imino}methyl)benzenol (“emSib”, 2a ), 2‐({[2‐(methylsulfanyl)ethyl]imino}methyl)benzenol (“mSib”, 2b ), 2‐(1‐ethylpropyl)‐6‐({[2‐(methylselanyl)ethyl]imino}methyl)benzenol (“emSEib”, 2c ), and 2‐({[2‐(methylselanyl)ethyl]imino}methyl)benzenol (“mSEib”, 2d ) were prepared by treatment of salicylaldehyde derivative 1a or salicylaldehyde 1b with 2‐(methylsulfanyl)‐ or 2‐(methylselanyl)ethylamine (or their hydrochlorides), according to a procedure recently published by us 8. In the 1 H NMR spectra of 2a – d , the signal of the phenolic proton at δ = 13.30 ppm ( 2b , d ) or 13.50 ppm ( 2a , c ) is consistent with hydrogen bonding between the hydroxy and the nitrogen of the imine group 10.…”

“…General: 3‐(1‐Ethylpropyl)‐2‐hydroxybenzenecarbaldehyde ( 1a ),12 2‐(methylsulfanyl)ethylamine,13 and 2‐(methylselanyl)ethylamine8 were prepared by known procedures. Syntheses of ligands emSib ( 2a ) and emSEib ( 2c ) have been described by us elsewhere 8. Ligands mSib ( 2b ) and mSEib ( 2d ) were prepared according to the same procedure.…”

Synthesis of New Sterically Hindered Anilines

“…Other significant recent applications are as structural elements in dye materials,2a,2b and biologically active compounds 3a,3b. We have recently reported the one‐step conversion of a range of methyl‐substituted aromatic molecules to the corresponding 1‐ethylpentyl derivatives by means of the superbase system4,5 n BuLi/LiK(OCH 2 CH 2 NMe 2 ) 2 in the presence of Mg(OCH 2 CH 2 OEt) 2 ,6,7 and we have also reported on the chemistry of the compounds obtained 8–10. We now report an adaptation of this methodology to the ethylation of methyl‐ and ethyl‐substituted primary, secondary and tertiary anilines to new compounds which demonstrate a range of steric hindrance around the amino group and complement other bulky primary ring‐alkylated anilines that we have reported recently, and which were prepared in two steps from the corresponding hydrocarbons by nitration and subsequent reduction 9…”

Syntheses, spectral characterization, thermal properties and DNA cleavage studies of a series of Co(II), Ni(II) and Cu(II) polypyridine complexes with some new schiff-bases derived from 2-chloroethylamine

“…These bands were absent in all the complexes, indicating deprotonation on coordination of the Schiff base ligands to metal ion. In addition, the bands at 1346-1350 cm -1 attributed to the phenolic C-O stretching vibrations of the free ligands were blue-shifted to 1341-1431 cm -1 upon complexation suggesting the involvement of the phenolic oxygen atom in the coordination [18][19][20]. The imine (C=N) functional group of the free ligands was observed as strong bands between 1670-1643 cm -1…”