CS261434B1 - Photochromic 2,4,4, fi tetrafenyl-4 H-pyrans and the process for their preparation - Google Patents

Abstract

Photochromic 2,4,4,6-tetraphenyl-4H-pyrans of general formula I, where X is alkyl having 1 to 2 carbons, alkoxyl having 1 to 2 carbons or halogen, have photochromic properties. The method of their production consists in using a dehydrating agent for 1,3,3,5-tetraphenyl-1,5-pentadiones of the general formula II, where X has the above-mentioned meaning, in an organic solvent.

Description

261434

The present invention relates to a 2,4,4,6-teraphenyl-4H-pyran of the formula I wherein X is alkyl, the number of carbon atoms is 1 to 2, the alkoxy group is 1 to 2, and the halogen.

So far, only a derivative has been prepared in which X is hydrogen atoms in two ways. The first method is the phosphorus dehydration of 1,3,3,5-tetrafenyl-1,5-pentanedione, the latter being treated with phenylmagnesium bromide to 1,3,5-triphenyl-2-pentene-1,5-dione, to yield a 4H- and 2H-pyran mixture.

The newly prepared 4H-pyrans in the crystalline state show a distinct photochromic irradiation with sunlight. The 4H-pyrans are potential components of light-sensitive layers useful in microelectronics.

The process for the preparation of 4H-pyran of general formula I according to the invention consists in the fact that the 1,3,3,5-tetrafenyl-1,5-pentanedione of the general formula II wherein X has the aforementioned meaning is treated with a suitable dehydrating agent. As dehydrating agents, phosphorus pentoxide, acetic anhydride, p-toluenesulfonic acid, iodine, or primary ammonium salts are used in the boiling organic solvent. As the solvent, organic acids or aromatic hydrocarbons are used.

The preparation of 4H-pyran of formula I and their photochromic properties are shown in the following examples. Example 1

Method of producing 4H-pyran I (X = CH3)

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A mixture of 1.77 g (4 mmol) of 3,3-diphenyl-1,5-bis (p-tolyl) -1,5-pentadione and 4.48 g (27.2 mmol) of phosphorus pentoxide was overlaid with 20 ml xylene and heated for 3 hours with a reflux condenser, while boiling the phosphorus pentoxide dried nitrogen solvent. After cooling, the xylene solution was poured and concentrated in vacuo. 0.92 g of 2,6-bis (p-tolyl) -4,4-diphenyl-4H-pyran was precipitated from the petroleum ether by distillation, representing a 54% yield. Crystallization of the xylene / petroleum ether mixture gave a pure substance, m.p. 188-189 degrees Celsius. Example 2

Method of producing 4H-pyran I (X = OCH3)

A mixture of 1.88 g (4 mmol) of 3,3-diphenyl-1,5-bis (p-methoxyphenyl) -1,5-pentadione and 4.48 g (27.2 mmol) of phosphorus pentoxide treated in a similar manner as in Example 1. 0.74 g of 4,4-diphenyl-2,6-bis (p-methoxyphenyl) -4H-pyran is obtained in 41% yield. A pure product was prepared by crystallization from a mixture of ethylene and petroleum ether, m.p. 215-217 ° C. Example 3

Method of production of 4H-pyran I (X == Br)

A mixture of 2.26 g (4 mmol) of 3,3-diphenyl-1,5-bis (p-bromophenyl) -1,5-pentadione and 4.48 g (27.2 mmol) of phosphorus pentoxide treated in a similar manner as in Example 1. 1.27 g of 2,6-bis (p-bromophenyl) -4,4-diphenyl-4H-pyran product was obtained, yielding 58% yield. The crystallization of the xylene / petroleum ether mixture was prepared as a pure substance with a melting point of 262-263 ° C. 52%.

Using phosphorus pentoxide as a dehydrating agent, 2,6-bis (pfuorphenyl) -4,4-diphenyl-4H-pyrane was prepared analogously to yield 52%, mp 235-237 ° C. . Example 4

Photochromic properties of substances I

The light-indicated color change of the substance was observed in the solid state. When irradiating the solid samples of substances I, the required exposure time ranges from fractions of a second to a few minutes. Keeping the color crystals dark in the course of several hours leads to color loss. A similar effect can be obtained when the substance is dissolved or heated. Substance I Color of substance Substance color before irradiation X = CH3 colorless blue X = OCH3 colorless blue X = Br colorless blue

Claims (4)

2 6 1 4 3 4 5 SUBJECT What is claimed is: 1. Photochromic 2,4,4,6-tetrafenyl-4H-pyranes of formula I wherein X is alkyl having from 1 to 2, alkoxy having from 1 to 2, or halogen. 2. A process for the preparation of 2,4,4,6-tetraphenyl-4H-pyranes of the general formula I according to claim 1, characterized in that they act on the 1,3,3,5-tetrafenyl- 1,5-pentadienyl general formula II wherein X is as defined above in an organic solvent. VYNALEZU 3. A process according to claim 2 wherein the dehydrating agents are phosphorus pentoxide, acetic anhydride, p-toluenesulfonic acid, iodine or primary ammonium salts in a boiling organic solvent. 4. A process as claimed in claim 1, wherein organic acids or aromatic hydrocarbons are used as the solvent.