Anomalies in the Reduction of the Schiff Bases 5-(Diethylamino)-2-(phenyliminomethyl)phenol and 2-[(4-Diethylaminophenyl)iminomethyl]-phenol and Their Crystal Structures

Abstract

Two intermediate Schiff bases, 5-( diethylamino )-2-( phenyliminomethyl )phenol(1) and 2-[(4-diethylaminophenyl) iminomethyl ]phenol(2), were encountered which proved difficult to reduce to their corresponding secondary amines with sodium borohydride . X-Ray crystallographic analyses showed that the molecules are virtually planar with intramolecular hydrogen bonding between the imino nitrogen and the phenolic oxygen. Bond lengths in the phenyl rings with the diethylamino substituents indicate a significant contribution from the quinonoid form for these ring systems.

Synthesis, X-ray Structure, Spectroscopic Properties and DFT Studies of a Novel Schiff Base

“…The dominance of an enol-form for 1 – 4 , namely intramolecular hydrogen-bond formation between O–H and N, is well supported by a combination of 1 H NMR and X-ray single-crystal analyses [ 72 , 73 ]. In the 1 H NMR studies, the existence of a strong hydrogen bond between O–H and N is evidenced by the observation of a large downfield shift of the proton peak at δ > 12 ppm for all salicylideneaniline derivatives 1 – 4 , the values of which are in the order of 3 (13.85 ppm) > 1 (13.26 ppm) > 4 (12.74 ppm) > 2 (12.12 ppm) in dry CDCl 3 ( Table 1 ).…”

A dipodal molecular probe for naked eye detection of trivalent cations (Al3+, Fe3+and Cr3+) in aqueous medium and its applications in real sample analysis and molecular logic gates

“…This was prepared by following reported procedures. 22,23 Freshly distilled aniline (0.93 g, 10 mmol) in dry methanol (20 mL) was slowly added to a well stirred solution of 4-(diethylamino)salicylaldehyde (1.93 g, 10 mmol) in dry methanol (40 mL), and the resulting orange yellow solution was stirred for a further 3 h. The reaction mixture was concentrated in vacuo, the residue was puried by ash SiO 2 column chromatography eluting with hexane/AcOEt. Orange yellow crystalline compound were ltered off, washed with cold methanol, then recrystallized from ethanol to give orange single crystals.…”

Schiff Bases and Stereocontrolled Formation of Fused 1,3-Oxazolidines from 1-Amino-2-Indanol: A Systematic Study on Structure and Mechanism

“…All structures elucidated by single-crystal diffraction exhibit a strong intramolecular hydrogen bond leading to a six-membered ring whose geometric characteristics are collected in Table S2 . Table 1 compares some bonding distances obtained by X-ray analyses of 24 and 40 – 41 , with the average values of similar structures described as phenoliminic tautomers [ 12 , 13 , 14 , 15 , 16 , 17 , 18 , 19 , 20 , 21 , 22 , 23 , 24 , 25 , 26 , 27 , 28 , 29 , 30 , 31 ] and ketoamines [ 32 , 33 , 34 ] in the Cambridge Structural Database ( Figure 13 ). The analysis of bond distances in compounds 40 and 42 indicates that the values of d C2-C3 and d C4-O5 are in full agreement with an enamine structure.…”