2,3-Dihydro-2 spiro-4 - -perimidine

Valence and prototropic tautomeric reactions are among the most important mechanisms that govern transformations of a broad variety of photochromic organic systems.1,2 Until recently, no examples of photochromic compounds have been reported whose photochromic behavior was due to a combination of these two tautomeric reactions. Such a combination, which is characteristic of ring-chain tautomerism3 has been implemented in the photochromic and thermochromic rearrangements of a novel type of heterocyclic photochromes, derivatives of 2,3-dihydro-2-spiro-4 -(2, 6 -di-iert-butylcyclohexadien-2, 5 -one)perimidine la and its analogs.4 The occurrence of a proton transfer step is in accord with the fact that the AvV -dimethyl derivative of la exhibits no photochromic properties. 

On prolonged passing of air through ethanol or acetonitrile solutions of 1 (R = H) in a quartz photoreactor with an immersed mercury lamp, 2, 3 -dihydro-2 -spiro-4-(2,6-di- ert-butylcyclohexadien-2,5-one)perimidin-4 -one 14 was isolated as the main product of the photooxidation reaction. With the A W -dimethyl derivative of 1, photooxidation results in the formation of the perimidinedione 15.12... 

A mixture of 1,8-naphthalenediamine (3.48 g, 22 mmol), 2-tert-butyl-1,4-naphthoquinone (3.21 g, 15 mmol) and p-toluenesulfonic acid (50 mg) was melted together at 165-170°C for 4 h, cooled to room temperature and dissolved in chloroform (20 ml). The solution was passed through a column (40 x 3.5 cm) filled with A120 3. The column was washed with chloroform-hexane (1 3) and the fraction of orange color collected. After evaporation of the solvent, dark-yellow crystals of 2,3-dihydro-2-spiro-4 -[(4H)-2 -fert-butlnaphthalen-l -one]perimidine (2.06 g, yield 47.8%) were obtained, mp 211-213°C (after recrystallization from methanol and heptane). 

---