Photo-and thermochromic spiranes. 24. Novel photochromic spiropyrans from 2,4-dihydroxyisophthalaldehyde

Abstract

Novel series of photochromic indoline and benzoxazine spiropyrans containing ortho-placed formyl and hydroxyl groups in the benzene ring of the chromene part of the molecule have been prepared. X-ray analysis has shown that, depending on the structure of the heterocyclic component in the spiro cyclization reaction different, nonequivalent formyl groups of 2,4-dihydroxyisophthalaldehyde can participate. The synthesized compounds were used as original analogs of salicylaldehyde. The novel photochromic bispyropyrans prepared contain two different asymmetric spiro carbon atoms.The photochromic properties of spiropyrans are determined not only by a contribution from the heterene fragment but to a greater extent by the substituents in the 2H-chromene part of the molecule. We have prepared the novel spiropyrans 4 and 6 which are original analogs of salicylaldehyde. The spiropyrans 7 have been prepared from compound 4 and they contain two different spirocyclic centers and hence two asymmetric carbon atoms. The structures of the synthesized compounds 4, 6, 7 were confirmed by elemental analysis (Table 1) and by IR and 1 H NMR spectroscopy ( Table 2). The IR spectra of compounds 4, 6 show absorption bands at 1584-1633 and 912-996 cm -1 (ν C=C and ν C-O in the 2H-chromene fragment respectively) and in the spiropyrans 4 and 7 there are also carbonyl stretching bands from the benzoxazinone fragment at 1673-1686 cm -1 . In the IR spectra of the spiropyrans 4 and 6 the absorption bands for the formyl and hydroxyl groups are absent. Evidently this is connected with a strong intramolecular hydrogen bond (IHB). The 1 H NMR spectrum of compound 4a in deuterochloroform shows signals for the 3' and 4' protons as an AB-spectrum with δ (3') = 5.97 and δ (4') = 6.93 ppm (J 3'4' = 9.8 Hz). The N-CH 3 methyl group signal at position 3 of the oxazinone fragment, the formyl proton, and the OH proton placed ortho to it in the benzene ring of the 2H-chromene fragment appear as singlets at 3.17, 10.22, and 11.69 ppm respectively.In the indoline spiropyrans of series 6 the gem-dimethyl groups in position 3 are a convenient diastereotopic marker reflecting the spiropyran structure of the compound. The presence in the 1 H NMR spectrum of two singlet signals for the gem-dimethyl groups (gem (CH 3 ) 2 ) at δ = 1.15 and 1.25 ppm (in the case of compound 6a) is due to the presence in the molecule of an asymmetric carbon atom and confirms the _______ * For Communication 23 see [1]. __________________________________________________________________________________________

Photo- and thermochromic spiranes 32*. Synthesis and photochromism of 3-methyl-4-oxospiro(2,3-dihydronaphtho-[2,1-e]-1,3-oxazine-2,2'-[2H]-chromenes)

“…The nonplanarity of the analogous fragments in the independent 4c-B molecule is caused by twists along the lines N(23)···O(21) at an angle of 30.3° and C(23')-O(21') and C(24')-O(21') at angles of 15.9° and 5.4° respectively. The previously studied compound 6 without the additionally annelated benzene ring has a similar structure [6]. The nonplanarity of the benzoxazinone fragment in this compound is caused by a twist along the line of N (3) The geometric structure of the C spiro -node and the benzopyran fragment in the independent molecules of compound 4c are analogous to the structure of the previously investigated indoline and benzoxazine spiropyrans.…”

“…Another direction for the modification of properties of photochromic spiropyrans, to which the current investigation is devoted, consists of varying the hetarene component and studying the effect of its structure on the photodynamic characteristics of spiropyrans. The present work is a continuation of our investigations in [6]. _______ * For Communication 31 see [1].…”

Multifunctional Spirocyclic Systems

“…Previously we synthesized and studied number of spiropyrans of benzoxazinone and indoline series [5]. We decided to continue our research of aldehyde-substituted spirocompounds.…”

The Effect of Tb and Sm Ions on the Photochromic Behavior of Two Spiropyrans of Benzoxazine Series in Solution

“…] benzopyran] SP(II) were described previously [16,17]. Spectroscopic pure grade solvents were used.…”