Synthesis, properties and X‐ray structure of 5‐azido‐2‐methoxy‐1,3‐xylyl‐18‐crown‐5

Abstract

5-Azido-2-methoxy-1,3-xylyl-18-crown-5 has been prepared by reacting p-toluenesulfonyl azide with the carbanion generated from the reaction of 5-bromo-2-methoxy-1,3-xylyl-18-crown-5 with n-butyl lithium. The asymmetric N 3 stretch of this product has been observed as a single band at 2110 cm -1 in dichloromethane solution. Addition of solid NaSCN, KSCN and CsSCN shifts this band to 2115, 2113 and 2112 cm -1 , respectively. Computational studies of this azide at the B3LYP-6-31G* level in the presence and absence of Na + predicted these bands to be at 2173 cm -1 and 2184 cm -1. For the salt-containing solutions, additional bands were observed at 2066 cm -1 , 2056 cm -1 and 2055 cm -1 , respectively, which are in the range expected for CN stretches. The X-ray structure of this azide has been determined. The terminal and internal N-N bond lengths were found to be 1.127(2) and 1.245(2) , respectively, which is the usual pattern for aromatic azides. The crown ether is looped over the face of the aromatic ring resulting in an angle of 38.94° between the plane defined by the aromatic ring and that defined by the five ring oxygen atoms. In addition, the CH 3 group is rotated out of the plane of the phenyl ring with C1-C18-O181-C182 and C17-C18-O181-C182 dihedral angles of 93.81(14)° and -90.54(14)°, respectively.

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“…After the click reaction between HENCC-AK and HENCC-AZ, the obtained FTIR spectra are shown in Figure . The HENCC-AZ has a characteristic peak at 2110 cm –1 as shown in Figure a, which is for the stretching of -N3 groups . The small peak at 1740 cm –1 , is for the carboxyl vibrations in acid conditions, which are from the remaining carboxyl groups which were not completely reacted with azide groups, since part of the carboxyl groups located inside of the bundle of the DCC chains are not easily accessible.…”

“…The HENCC-AZ has a characteristic peak at 2110 cm −1 as shown in Figure 6a, which is for the stretching of -N3 groups. 29 The small peak at 1740 cm −1 , is for the carboxyl vibrations in acid conditions, 20 which are from the remaining carboxyl groups which were not completely reacted with azide groups, since part of the carboxyl groups located inside of the bundle of the DCC chains are not easily accessible. Compared with the intensity of the peak at 1020 cm −1 , the number of carboxyl groups has been dramatically reduced after the hydrolysis of ENCC (Figure 4c).…”