A Facile Synthesis of New Chiral [1+1] Macrocyclic Schiff Bases

Abstract

A series of new chiral [1+1] macrocyclic Schiff bases have been synthesized in high yields and short reaction times from cyclocondensation of dialdehydes with long tethers and chiral diamines. The yields of the macrocycles were higher when the dialdehyde component is also chiral. The macrocyclisation was performed under microwave irradiation and aqueous reaction conditions employing salts of chiral diamines in contrast to free diamines normally employed.

(E)-N′-(5-Chloro-2-hydroxybenzylidene)-3,5-dihydroxybenzohydrazide monohydrate

“…For background to the synthesis of Schiff base compounds, see: Herrick et al (2008); Suresh et al (2007). For the biological activity of Schiff base compounds, see: Bhandari et al (2008); Sinha et al (2008).…”

“…Data collection: SMART (Siemens, 1996); cell refinement: SAINT (Siemens, 1996); data reduction: SAINT; program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: SHELXTL (Sheldrick, 2008); software used to prepare material for publication: SHELXTL. Schiff base compounds can be easily synthesized from the reaction of aldehydes with primary amines (Herrick et al, 2008;Suresh et al, 2007). These compounds show interesting biological activities, especially antimicrobial activities (Bhandari et al, 2008;Sinha et al, 2008).…”

N′-(3,5-Dichloro-2-hydroxybenzylidene)-3-methoxybenzohydrazide methanol solvate

“…For the synthesis of Schiff base compounds, see: Herrick et al (2008); Suresh et al (2007); Liu et al (2007). For the background on biological activities, see: Bhandari et al (2008); Sinha et al (2008); Sun et al (2008).…”

“…Data collection: SMART (Bruker, 2002); cell refinement: SAINT (Bruker, 2002); data reduction: SAINT; program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: SHELXTL (Sheldrick, 2008); software used to prepare material for publication: SHELXL97. Schiff base compounds can be easily synthesized from the reaction of aldehydes with primary amines (Herrick et al, 2008;Suresh et al, 2007;Liu et al, 2007). These compounds show interesting biological activities, especially antimicrobial activities (Bhandari et al, 2008;Sinha et al, 2008;Sun et al, 2008).…”

(E)-N′-(4-Bromobenzylidene)-3,4-dihydroxybenzohydrazide monohydrate

“…For the synthesis of Schiff base compounds from the reaction of aldehydes with primary amines, see: Herrick et al (2008); Suresh et al (2007). For a related structure, see: Ma et al (2008).…”