Synthesis and structural studies of 5,7(4,6)-di(tert-butyl)-2-(6,8-dimethyl-4-chloroquinolin-2-yl)-1,3-tropolones by quantum-chemical methods and two-dimensional correlation NMR spectroscopy

Rearrangement of a 5,7-di-tert-butyl-2-(quinolin-2-yl)-1,3-tropolone into a pentalene derivative

“…the predominance of the N-H tautomeric form. This is confirmed by the 1 H- 13 C HMBC spectrum of isomer 3, in which cross-peaks of the proton signal of the N-H … O-group at δH 15.63 ppm with atoms С(4'a) and С(3') of the quinoline ring and connecting carbon C(2) at δC 107.0 ppm of the formed pentalene substituent in the second position of the quinoline are present. In the 1 H- 15 N HMBC spectrum of the isomer 3 cross-peaks of the 15 N signal with protons of the N-H … O-group and H(3') of the quinoline ring are present.…”

“…Also one of the protons of the tropone ring changes its position upfield from 6.5-7.0 ppm to 3.20 ppm, while the second tropone proton undergoes a downfield shift to 7.19 ppm. In the 13 C NMR spectrum of 3 both signals of the С=О groups are downfield shifted by approximately 1.0-1.5 ppm. Instead of the disappearing signals at δc 125.1 and 122.9 ppm and one of the signals of carbons, carrying the tert-butyl group at δc 153.0-155.5 ppm, the number of alkyl carbons in the ring increases, which is revealed at δc 50.9, 43.7, and 69.0 ppm.…”

“…The structure of compound 3 was established using a combination of methods: mass-spectroscopy, IRspectroscopy, NMR 1 Н, 13 С, COSY, HSQC, 1 Н-13 С and 1 H- 15 N HMBC, and X-ray analysis. In the course of determination of the structure, the 1 H and 13 C signals of compound 3 were completely assigned (Figure 1). A comparison with the NMR spectra of the initial tropolone 1 was made as well.…”

“…In the 1 H- 15 N HMBC spectrum of the isomer 3 cross-peaks of the 15 N signal with protons of the N-H … O-group and H(3') of the quinoline ring are present. The cross-peaks coordinates of the 1 H- 13 C HMQC and HMBC heteronuclear correlations are given in Table 1. 13 C HMBC correlations of compound 3.…”

“…The cross-peaks coordinates of the 1 H- 13 C HMQC and HMBC heteronuclear correlations are given in Table 1. 13 C HMBC correlations of compound 3.…”