Syntheses, spectroscopic properties and stereochemistry of bis-C-pivot macrocycles with two dialkyl phosphonate groups

Bis-C-pivot macrocycles containing dimethyl (1a, 2a) or diethyl phosphonate (1b, 2b) groups have been prepared by adding dimethyl or diethyl phosphite to two -CH=N bonds in corresponding dibenzo-bis-imino crown ethers (1 and 2). Bis-C-pivot macrocycles possess two equivalent stereogenic centres giving rise to diastereoisomers (mess and racemate). The structures were characterized by elemental analysis, FTIR, MS, TGA, DSC and NMR measurements. H-1, C-13 and P-31 NMR assignments were made for the isolated mess form of compounds 2a and 2b and for the mesa and racemic forms of compounds 1a and 1b by analysis of chemical shifts, signal intensities and splitting patterns and the DEPT and 2D HETCOR NMR techniques. Thermal analysis and H-1 NMR showed that the crystallised form of compound 1a contained an equimolar amount of water of crystallisation. (C) 2011 Elsevier B.V. All rights reserved.