Spiro indoline-oxazines

C. Salemi, G. Giusti, and R. Guglielmetti, DABCO effect on the photodegradation of photochromic compounds in spiro[indoline-pyran] and spiro[indoline-oxazine] series, J. Photochem. Photobiol. A Chem., 86, 247-252 (1995). 

P. Lareginie, V. Lokshin, A. Samat, R. Guglielmetti, and G. Pepe, First permanent opened forms in spiro[indoline-oxazine] series synthesis and structural elucidation, J. Chem. Soc., Perkin Trans., 2,... 

Favaro et al. studied the kinetic and thermodynamic behavior of seven spiro[indoline-oxazines], (29 and 32-37).15-17 The investigated molecules exhibited thermochromism in a polar solvent (ethanol) but not in a nonpolar solvent (methylcyclohexane). From thermodynamic data and the kinetic parameters of the bleaching reaction, the rate constants and the activation energies for the thermal... 

Pettier, E., Dubest, R., Guglielmetti, R., Tardieu, P., KeUmann, A., Tfibel, F., Levoir, R, and Aubard, J., Effets de substituent, d h teroatome et de solvant sur les cin tiques de d colorora-tion thermique et les spectres d absorption de photomerocyanines en s rie spiro[indoline-oxazine], Helv. Chim. Acta, 73, 303,1990. 

Finally, we note the reversible solution-phase rearrangement of a collection of 1,3,3-trialkylated derivatives of spiro[indoline-2,3 [3//]naphth[2,l-b][l,4]oxazines and the corresponding 2-[2-oxo-l-naphthylidenoiminomethylene]indolines for which the enthalpy of reaction is known38, but these studies unfortunately fail to provide us any useful thermochemical information, such as enthalpies of formation. 

Indolines, benzoxazole, and benzothiazole are possible as 2-methylene heterocycles. The number of known spirooxazine derivatives is much less than for the spiropyrans. This may be partly due to lack of many substituted o-nitrosonaphthols and partly due to lack of sufficient stability of spiro-oxazines. The structures of parent spirooxazines and the Xmax of their photomerocyanine forms are listed in Table 5. The Xmax of the colored forms of compounds 41-43 are not described in the literature. 

Two permanent merocyanines have been reported for the spiro-oxazines [85]. These were NOSH heteroanellated by imidazo [l,2-a]pyridine and imidazo [l,2-a]pyrimadine. Several tests have been conducted to determine the nature of these species. H -NMR data show that the indoline nitrogen is not highly charged and the crystal structure indicates that the ground state is essentially the quinoidal form. The most stable form was found to be the TTC isomeric form by x-ray analysis. The dipole moment of these permanent spiro-oxazine merocyanines was around 3.84 D, which is much lower than the values reported for spiropyran merocyanines. 

Schneider et al. [63] investigated the photochemistry of the spiro-oxazine merocyanines pumping and probing at 570 nm in acetonitrile. The found that the solution bleached within the <5-psec pulse duration. The bleached state recovered with at least a biexponential behavior, and from their fluorescence decay measurements, three exponentials were required to fit the decay. They attribute these findings to the possibility of three merocyanine isomers that are in equilibrium. Their compounds feature geminal ethyl groups on the indoline moieties and this may influence the system as compared to NOSIl. 

Condensation of 2-methylene indoline derivatives 816 with l-nitroso-2-naphthol (817) under MWI gave spiro indolinonaphth[2,l-6][l,4]oxazines 818 in 11-61% yields within 12 min. When the same reaction was carried out in the presence of morpholine, 819 were also formed in 19-34% yields (Scheme 155) (04SC315). 

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