THERMOCHROMIC AND PHOTOCHROMIC DYES - SPIRO(INDOLINEBENZOPYRANS) .2. DETAILED ASSIGNMENT OF THE H-1-NMR SPECTRA AND STRUCTURAL ASPECTS OF THE CLOSED FORM OF 1,3,3-TRIMETHYLSPIRO(INDOLINE-2,2'-BENZOPYRANS)

The proton NMR assignments for a series of 12 thermo- and photochromic 1,3,3-trimethylspiro(indoline-2,2'-benzopyrans) dyes is reported. All of the protons in the dye molecule were assigned through a combination of homonuclear decoupling experiments and correlation spectroscopy. The relative stereochemistry of the indolino gem-dimethyl groups was assigned so that, for the S-epimer, the pro-R methyl was found to resonate at 1.24 ppm while the pro-S methyl appeared at 1.37 ppm for compound 1.