US3149120A - 3, 3'-dimethyl-6'-nitro-spiro - Google Patents

Description

United States Patent lllaryland No Drawing. Filed Feb. 15, B62, Ser. No. 173,355 1 Claim. (Cl. 260-307) This invention relates to 3-alkyl,3-alkyl-spiro-[benzoxaZole-2,2-(2H-1-benzopyran)] compounds, having the formula Alkyl Alkyl -wherein Ra represents one or more independently selected radicals, to be specified hereinafter, at one or more of the 4, 5, 6, 7, 5, 6, 7, and 8 positions.

This application is a continuation-in-part of co-pending United States patent application Serial No. 87,534, filed February 7, 1961, now abandoned, which is a continuation-in-part of United States patent application Serial No. 827,463, filed July 16, 1959, in the names of Elliot Berman and David B. McQuain, inventors, and which is now abandoned.

These compounds in solution are substantially colorless but may be changed, at will, to a colored state, in which the 2'-1 bond is broken, by being subjected to light predominating in components from blue through ultraviolet wave-lengths, and reversed back, at will, in solution, to the substantially colorless state by such solutions being subjected to light predominating in components of wavelengths in the green through infra-red region of the spectrum.

These compounds are useful in sensitizing record materials so as to exhibit data by colored and uncolored areas thereon, which data has been selectively recorded thereon, or erased therefrom, by the application of recording light or erasing light or heat.

Solutions of the compounds are also useful as components of optical filters which darken on being subjected to ultra-violet or blue light, such filters being adapted for protecting the eyes from tissue-damaging light or from temporarily-induced blindness from excessive light, inasmuch as they respond immediately to the coloring light waves which accompany great excesses of visible light.

Reference is made to an application of applicant'Elliot Berrnan for United States Letters Patent, Serial No. 827,- 420, filed July 14, 1959, for details of how the novel derivative compounds of this application may be incorpo rated in an eye-protecting filter. Reference also is made to applicant Elliot Bermans application for United States Letters Patent Serial No. 654,578, filed April 23, 1957 (which issued into United States Patent No. 2,95 3,454 on September 20, 1960), relative to the use of such compounds in a record sheet on which data may be selectively recorded by light, and erased therefrom by light.

These compounds vary in their stability, due to thermal activity, the unsubstituted compound being reversibly colorable and stable in solution in the colored state only at low temperature-say, about minus 60 degrees centigradein the absence of change-provoking light, whereas those derivatives which have substituents in any of the unoccupied positions in the benzene rings which tend to weaken the spiro-carbon-to-oxygen 2'-1' bond, and are reversibly colorable, are characterized by having a useful but limited thermal stability at higher temperatures, even above normal human activity temperatures.

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It should be understood that the novel compounds of this invention will, in the absence of exposure to shortwave-length change-provoking light, remain in the colorless state indefinitely, when in solution, either at or about normal room temperatures; and that said compounds when in the colored states, in solution, not only will quickly revert to the colorless form by the action of longer-wave-length change-provoking light, but will also, even in the dark, rapidly revert to said colorless state, by thermal activity, at or about normal room temperatures. The rate of reversion is temperature-dependent, the rate increasing with increasing temperature. The rate at which these compounds revert from the colored form to the colorless form is normally expressed as the half-life of the colored form of the compound and is a quantitative measure of the thermal stability of such compounds at or about room temperature. It has been found that, when properly modified, various classes of compounds, particularly spiropyran compounds, may be made in which the room temperature thermal stability of the colored form varies from a half-life of a fraction of a second to a half-life of several months. The thermal stability of the novel compounds of this invention fall in the short half-life portion of this range, the half-life, on

the average, varying from about one minute to about ten minutes.

In contrast, the 3-alkyl,3'-alkyl-spiro[benzothiazole- 2,2-(2H-1'-benzopyran)] compounds disclosed and claimed in applicants commonly-owned United States patent application Serail No. 173,334, filed on February 15, 1962, unexpectedly have far greater room or higher temperature thermal stability than the compounds of this invention, the stability of the former, expressed in terms of the halflives of the colored states, being, in general, about twenty-four hours. It is thus apparent that, even though the compounds of the instant invention are the analogs of the compounds disclosed in the above-mentioned co-pending application, the difference in room temperature thermal stability between the two classes is completely unexpected and unobvious, and that the thermal stability found in one class has no quantitative relation to the stability found in the other.

A suitable method for determining the half-life of the colored form of the instant compounds is to determine, at a selected wave-length, the rate of decrease in absorbence of a solution of the compounds wlr'le kept in the dark, over a known time interval, and, by the use of wellknown rate formulas and a graph plot of the variables, to calculate the interval of time required for the absorbence to decrease from a maximum value to half this value.

By the term solution, as used herein, is meant the homogeneous mixture of one or more of the claimed compounds with a solid or liquid substance.

By the term stable, as used in this application, it is meant that the compounds of this invention have considerably less room temperature thermal stability than numerous related compounds from different classes of spiro-pyran compounds; for example, such as the compounds disclosed in the above-specified co-pending application.

Among the many possible radicals which may be attached at any one of the 4, 5, 6, 7, 5', 6', 7, and 8 positions are the following: CH CH CH CH(CH the phenyl group C 21 (3P CN; COCH CO C H CO H; NR NHCH N(CH NHCOCH N(CH N0 S 3; 2 5; 2h 3; s s); OCOCH SCI-l SH; SCOCH SCN; SOCH SO CH SO NH S(CH F; Cl; Br; I; 10 CH CH CH and CO CH Any of the substituents or group of sterically compatible substituents may be selected for attachment at the specified positions, and such compounds may be preis pared by condensing the selectively substituted salicylaldehyde (to give substituents in the 6, 7', or 8' positions, as desired) with the selectively substituted 2-ethyl- 3-alkylbenzoxazole (to give substituents in the 4, 5, 6, or 7 positions, as desired.) The 3-alkyl group may be introduced by suitable selection of an alkyl ester of ptoluene sulfonic acid.

Compounds related to the novel compounds of this invention, but without the 3-methyl group, have previously been disclosed by Bloch-Chaud in Cahiers Physique, volume 50, pages 17 to 53; volume 51, pages 6 to 42; and volume 52, pages 3 to 48; 1954. However, in contrast to the compounds of this invention, the compounds disclosed in that publication are not photochromic (not colorable by the action of light) at or about room temperatures. Such prior-art compounds are photochromic, if at all, only at very low temperatures, such as minus 60 degrees centigrade or below.

Preferably, however, some of the compounds most suitable for the uses and purposes described herein, wherein the compounds are reversibly colorable but have a low or reduced thermal stability in the colored form within the temperature range suitable for normal human activity, may be represented by the general structural formula R R7 Rs Example I As a preferred example, there will be described the preparation of 3,3'-dimethyl-6-nitro-spiro-(benzoxazole 2,2-[2'H,1-benzopyran] Thirty-one grams (0.28 mole) of o-aminophenol and 38 grams (0.28 mole) of propionic anhydride are placed in a 250-milliliter round-bottom flask and heated on a steam bath for two hours. The mixture is then heated to drive off the water and ammonia, and the residue is distilled at atmospheric pressure to yield 25 grams of a light-yellow oil with a boiling point of 214 to 217 degrees centigrade, which is 2-ethylbenzoxazole. The 2-ethylbenzoxazole, thus prepared, is placed in a lOO-milliliter round-bottom flask, and 32 grams (0.17 mole) of methyl-p-toluene sulfonate is added. The mixture is heated at 140 to 155 degrees centigrade for two hours and allowed to cool to room temperature. The resultant light-yellow solid is Washed several times with acetone to yield the second intermediate, 2-ethylbenzoxazole methyl-p-toluene sulfonate.

Next, in a 50-milliliter round-bottom flask are placed 5 grams (0.015 mole) of Z-ethylbenzoxazole methyl-ptoluene sulfonate, the second intermediate, and 2.5 grams (0.015 mole) of S-nitrosalicylaldehyde, 25 milliliters of pyridine as a solvent, and 1 milliliter of piperidine as a catalyst. The solution is heated on a steam bath for one hour and cooled, and the resulting precipitate is removed by filtration, which precipitate is recrystallized several times from ethanol, yielding light-yellow crystals of 3,3- dimethyl-6'-nitro-spiro-(benzoxaZole-2,2'-[2H,1' benzopyran] the desired compound.

Example II Preparation of 3,3'-dirnethyl-8'-nitro-spiro-(benzoxazole-2,2-[2H(l-benzopyran]): Place (0.28 mole of oaminophenol and (0.28 mole) of propionic anhydride in a 250-milliliter round-bottom flask and heat on a steam bath for two hours. The mixture then is heated to drive off the water and ammonia, and the residue is distilled at atmospheric pressure to yield a light-yellow oil with a boiling point of 214 to 217 degrees centigrade, which is 2-ethylbenzoxazole. The 2-ethylbenzoxazole, thus prepared, is placed in a -milliliter round-bottom flask, and (0.17 mole) of methyl-p-toluene sulfonate is added. The mixture is heated at to degrees centigrade for two hours and allowed to cool to room temperature. The resultant light-yellow solid is washed several times with acetone to yield the second intermediate, 2-ethylbenzoxazole methyl-p-toluene sulfonate.

Next, in a 50-milliliter round-bottom flask are placed (0.015 mole) of 2-ethylbenzoxazole methyl-p-toluene sulfonate, the second intermediate, and (0.015 mole) of 3-nitrosalicylaldehyde, 25 milliliters of pyridine as a solvent, and 1 milliliter of piperidine as a catalyst. The solution is heated on a steam bath for one hour and cooled, and the resulting precipitate is removed by filtration, which precipitate is recrystallized several times from ethanol, yielding light-yellow crystals of 3,3'-dimethyl- 8'-nitro-spiro-(benzoxazole-2,2' [2H,1 benzopyran] the desired compound.

Example III Preparation of 3,3-dimethyl-6'-chloro-8-nitro-spiro- (benzoxazole-2,2'-[2H,1'-benzopyran])z Place (0.28 mole) of o-aminophenol and (0.28 mole) of propionic anhydride in a 250-milliliter round-bottom flask and heat on a steam bath for two hours. The mixture is then heated to drive off the water and ammonia, and the residue is distilled at atmospheric pressure to yield a light-yellow oil with a boiling point of 214 to 217 degrees centigrade, which is Z-ethylbenzoxazole. The 2-ethylbenzoxazole thus prepared is placed in a l00-milliliter round-bottom flask, and (0.17 mole) of methyl-p-toluene sulfonate is added. The mixture is heated at 140 to 155 degrees centigrade for two hours and allowed to cool to room temperature. The resultant light-yellow solid is washed several times with acetone to yield the second intermediate, 2-ethylbenzoxazole methyl-p-toluene sulfonate.

Next, in a SO-milliliter round-bottom flask are placed (0.015 mole) of Z-ethylbenzoxazole methyl-p-toluene sulfonate, the second intermediate, and (0.015 mole) of 3- nitro-S-chlorosalicylaldehyde, 25 milliliters of pyridine as a solvent, and 1 milliliter of piperidine as a catalyst. The solution is heated on a steam bath for one hour and cooled, and the resulting precipitate is removed by filtration, which precipitate is recrystallized several times from ethanol, yielding light-yellow crystals of 3,3'-dimethyl-6-chloro-8-nitro-spiro-(benzoxazole-2,2'-[2H, 1'- benzopyran] the desired compound.

Example IV Preparation of 3,3'-dimethyl-6'-methoxy-8-nitro-spiro- (benzoxaZole-2,2'-[2H,1'benzopyran]): Place (0.28 mole) of o-aminophenol and (0.28 mole) of propionic anhydride in a 250-milliliter round-bottom flask and heat on a steam bath for two hours. The mixture is then heated to drive off the water and ammonia, and the residue is distilled at atmospheric pressure to yield a light-yellow oil with a boiling point of 214 to 217 degrees centigrade, which is Z-ethylbenzoxazole. The 2-ethylbenzoxazole thus prepared is placed in a IOO-milliliter round-bottom flask, and (0.17 mole) of methyl-p-toluene sulfonate is added. The mixture is heated at 140 to 155 degrees centigrade for two hours and allowed to cool to room temperature. The resultant light-yellow solid is washed several times with acetone to yield the second intermediate, 2-ethylbenzoxazole methyl-p-toluene sulfonate.

Next, in a 50-milliliter round-bottom flask are placed (0.015 mole) of Z-ethylbenzoxazole methyl-p-toluene sulfonate, the second intermediate, and (0.015 mole) of 3- 5 nitro-S-methoxysalicylaldehyde, 25 milliliters of pyridine as a solvent, and 1 milliliter of piperidine as a catalyst. The solution is heated on a steam bath for one hour and cooled, and the resulting precipitate is removed by filtration, which precipitate is recrystallized several times from ethanol, yielding light-yellow crystals of 3,3'-dimethyl-6'- methoxy 8-nitro-spiro-(benzoxazole-2,2'-[2'H,1-henzopyran] the desired compound.

Example V Preparation of 3,3'-dimethyl-6'-nitro-8'-methoxy-spiro- (benzoxazole-2,2'-[2'H,1'-benzopyran]): Place (0.28 mole) of o-aminophenol and (0.28 mole) of propionic anhydride in a 250-1nilliliter round-bottom flask and heat on a steam bath for two hours. The mixture then is heated to drive off the Water and ammonia, and the residue is distilled at atmospheric pressure to yield a light-yellow oil with a boiling point of 214 to 217 degrees centigrade, which is 2-ethylbenzoxazole. The Z-ethylbenzoxazole thus prepared is placed in a 100-milliliter round-bottom flask, and (0.17 mole) of methyl-p-toluene sulfonate is added. The mixture is heated at 140 to 155 degrees centigrade for two hours and allowed to cool to room temperature. The resultant light-yellow solid is washed several times with acetone to yield the second intermediate, 2-ethylbenzoxazole methyl-p-toluene sulfonate.

Next, in a 50-milliliter round-bottom flask are placed (0.015 mole) of 2-ethylbenzoxazole methyl-p-toluene sulfonate, the second intermediate, and (0.015 mole) of 3- methoxy-S-nitrosalicylaldehyde, 25 milliliters of pyridine as a solvent, and 1 milliliter of piperidine as a catalyst. The solution is heated for one hour on a steam bath and cooled, and the resulting precipitate is removed by filtration, which precipitate is recrystallized several times from ethanol, yielding light-yellow crystals of 3,3-dimethyl-6- nitro 8'-methoxy-spiro-(benzoxazole-2,2-[2'l-I,1-benzopyran] the desired compound.

Example VI Preparation of 3,3'-dimethyl-5-chloro-6'-nitro-spiro- (benzoxazole-2,2-[2'H,1-benzopyran]): Place (0.28 mole) of 2-amino-4-chlorophenol and (0.28 mole) of propionic anhydride in a 250-milliliter round-bottom flask and heat on a steam bath for two hours. The mixture then is heated to drive oil the water and ammonia, and the residue is distilled at atmosphic pressure to yield a light-yellow oil with a boiling point of 240 to 247 degrees centrigrade, which is 5-chloro-2 ethylbenzoxazole. The 5chloro-2-ethylbenzoxazole, thus pre-. pared, is placed in a l-milliliter round-bottom flask, and (0.17 mole) of methyl-p-toluene sulfonate is added. The mixture is heated at 140 to 155 degrees centigrade for two hours and allowed to cool to room temperature. The resultant light-yellow solid is washed several times with acetone to yield the second intermediate, S-chloro-Z- ethylbenzoxazole methyl-p-toiuene sulfonate.

Next, in a 50-milliliter round-bottom flask are placed (0.015 mole) of -chloro-2-ethylbenzoxazole methyl-ptoluene sulfonate, the second intermediate, and (0.015 mole) of S-nitrosalicylaldehyde, 2S milliliters of pyridine. as a solvent, and 1 milliliter of piperidine as a catalyst. The solution is heated on a steam bath for one hour and cooled, and the resulting precipitate is removed by filtration, which precipitate is recrystallized several times from ethanol, yielding light-yellow crystals of 3,3'-dimethyl-5- chloro 6 nitro spiro-(benzoxazole-2,2-[2'H,l'-benzopyran] the desired compound.

Example VII Preparation of 3,3,5-t.rirnethyl-6'-nitro-spiro-(benzoxazole-2,2'-[2'H,1'-benzopyran]: Place (0.28 mole) of 2-amino-4-methylphenol and (0.28 mole) of propionic anhydride in a 250-milliliter round-bottom flask and heat on a steam bath for two hours. The mixture then is heated to drive off the water and ammonia, and the residue is distilled at atmospheric pressure to yield a light-yellow oil with a boiling point of 228 to 235 degree centigrade, which is 5-methyl-2ethylbenzoxazole. ethylbenzoxazole thus prepared is placed in a -milliliter round-bottom flask, and (0.17 mole) of methyl-p-toluene sulfonate is added. The mixture is heated at to degrees centigrade for two hours and allowed to cool to room temperature. The resultant light-yellow solid is washed several times with acetone to yield the second intermediate, 5 methyl Z-ethylbenzoxazole methyl-ptoluene sulfonate.

Next, in a 50-milliter round-bottom flask are placed (0.015 mole) of 5-methyl-2-ethylbenzoxazole methyl-ptoluene sulfonate, the second intermediate, and (0.015 mole) of S-nitrosalicylaldehyde, 25 milliliters of pyridine as a solvent, and 1 milliliter of piperidine as a catalyst. The solution is heated on a steam bath for one hour and cooled, and the resulting precipitate is removed by filtration, which precipitate is recrystallized several times from ethanol, yielding light-yellow crystals of 3,3,5-trimethyl 6'-nitro-spiro-(benzoaxazole-2,2'-[2H,1' benzopyran1), the desired compound.

Example VIII reparation of 3,3-5-trimethyl-8-nitro-spiro-(benzoxazolea2,2-[2H,l-benzopyran]): Place (0.28 mole) of 2-amino-4-methylphenol and (0.28 mole) of propionic anhydride in a 250-milliliter round-bottom flask and heat on a steam bath for two hours. The mixture then is heated to drive oh the water and ammonia, and the resi due is distilled at atmospheric pressure to yield a lightyellow oil with a boiling point of 228 to 235 degrees centigrade, which is 5-methyl-2-ethylbenzoxazole. The 5-methyl-2-ethylbenzoxazole thus prepared is placed in a 100-milliliter round-bottom flask, and (0.17 mole) of methyl-p-toluene sulfonate is added. The mixture is heated at 140 to 155 degrees centigrade for two hours and allowed to cool to room temperature. The resultant lightyellow solid is washed several times with acetone to yield the second intermediate, 5-methyl-2 -ethylbenzo-xazole methyl-p-toluene sulfonate.

Next, in a SO-milliliter round-bottom flask are placed (0.015 mole) of 5-methyl-\2-ethylbenzoxazole methyl-ptoluene sulfonate, the second intermediate, and (0.015 mole) of 3-nitrosalicylaldehyde, 25 milliliters of pyridine as a solvent, and 1 milliliter of piperidine as catalyst. The solution is heated on a steam bath for one hour and cooled, and the resulting precipitate is removed by filtration, which precipitate is recrystallized several from ethanol, yielding light-yellow crystals of 3,3',5-trimethyl- 8-nitro-spiro-(benzoxazole-2,2-[2H,1' henzopyran]), the desired compound.

Example 1X Preparation of 3,3',5-trimethyl-6'-nitro 8'-methoxyspiro (benzoxazole-2,2'-[2H,1-benzopyran]): Place (0.28 mole) of 2-amino-4-methylphenol and (0.28 mole) of propionic anhydride in a 250-milliliter round-bottom flask and heat on a steam bath for two hours. The mixture then is heated to drive off the water and ammonia, and the residue is distilled at atmospheric pressure to yield a light-yellow oil with a boiling point of 228 to 235 degrees centigrade, which is 5-rnethyl-2-ethylbenzoxazole. The S-methyl-Z-ethylbenzoxazole, thus prepared, is placed in a lOO-milliliter round-bottom flask, and (0.17 mole) of methyl-p-toluene sulfonate is added. The mixture is heated at 140 to 155 degrees centigrade for two hours and allowed to cool to room temperature. The resultant light-yellow solid is washed several times with acetone to yield the second intermediate, S-methyl-Z-ethylbenzoxazole methyl-p-toluene sulfonate.

Next, in a SO-milliter round-bottom flask are placed (0.015 mole) of S-methyl-Z-ethylbenzoxazole methyl-ptoluene sulfonate, the second intermediate, and (0.015 mole) of 3-methoxy-5-nitrosalicylaldehyde, 25 milliliters The 5-methyl-2- of pyridine as a solvent, and 1 milliliter of piperidine as a catalyst. The solution is heated on a steam bath for one hour and cooled, and the resulting precipitate is removed by filtration, which precipitate is recrystallized several times from ethanol, yielding light-yellow crystals of 3,3',5- trimethyl-6-nitro-8'-methoxy-spiro- (benzoxazole 2,2- [2'I-l,l'-benzopyran] the desired compound.

Example X Preparation of 3,3,5,7atetramethyl-6 nitro-8'-methoxyspiro-(benzoxazole 2,2 [2H,1' benzopyran1) Place (0.28 mole) of 2-amino-4,6-dimethylphenol and (0.28 mole) of propionic anhydride in a -250-milliliter roundbottom flask and heat on a steam bath for two hours. The mixture then is heated to drive off the water and ammonia, and the residue is distilled at atmospheric pressure to yield a light-yellow oil, which is 5,7-dimethyl-2- ethylbenzoxazole. The compound thus prepared is placed in a 100-milliliter round-bottom flask, and (0.17 mole) of methyl-p-toluene sulfonate is added. The mixture is heated at 140 to 155 degrees cent-igrade for two hours and allowed to cool to room temperature. The resultant light-yellow solid is washed several times with acetone to yield the second intermediate, 5,7-dimethyl-2-ethylbenzoxazole methyl-p-toluene sulfonate.

Next, in a SO-milliliter round-bottom flask is placed (0.015 mole) of 5,7-dirnethyl-2-ethylbenzoxazole methyl-p-toluene sulfonate, the second intermediate, and (0.015 mole) of 3-methoxy-5-nitrosalicylaldehyde, 25 milliliters of pyridine as -a solvent, and 1 milliliter of piperidine as a catalyst. The solution is heated on a steam bath for one hour and cooled, and the resulting precipitate is removed by filtration, which precipitate is recrystallized several times from ethanol, yielding light-yellow crystals of 3,3,- 5,7-tetrarnethyl-6-n-itro-8-methoxy-spiro (benzoxazole- 2,2'-[2H,1'-benzopyran]), the desired compound.

Example XI Preparation of 3,3-dimethyl-5phenyl-6"nitro-spiro- (benzoxazole-2,2'-[2H,1 benzopyran1) Place (0.28 mole) of 2-amino-4-phenylphenol and (0.28 mole) of propionic anhydride in a 250-rnilliliter round-bottom flask and heat on a steam bath for two hours. The mixture is then heated to drive ofl the water and ammonia, and the residue is distilled at atmospheric pressure to yield a light-yellow oil with a boiling point of 150 to 165 degrees centigrade, which is 5-phenyl-2-ethylbenzoxazole. The compound thus prepared is placed in la 100-milliliter round-bottom flask, and (0.17 mole) of methyl-p-toluene sulfonate is added. The mixture is heated at 140* to 155 degrees centigrade for two hours and allowed .to cool to room temperature. The resultant light-yellow solid is washed several times with acetone to yield the second intermediate, 5-phenyl-2-ethyl-benzoxazole methyl-p-toluene sulfonate.

Next, in a SO-milliliter round-bottom flask are placed (0.015 mole) of 5-phenyl-Z-ethyl-benzoxazole methyl-ptoluene sulfonate, the second intermediate, and (0.015 mole) of S-nitrosalicylaldehyde, 25 milliliters of pyridine as a solvent, and 1 milliliter of piperidine as a catalyst. The solution is heated on a steam bath for one hour and cooled, and the resulting precipitate is removed by filtration, which precipitate is recrystallized several times from ethanol, yielding light-yellow crystals of 3,3'-dimethyl-5- phenyl-6-nitro-spiro-(benzoxazole 2,2 [2H,l-benzopyran]), the desired compound.

Example XII Preparation of 3,3-dimethyl-5-phenyl-6-nitro-8'-methoxy spiro (benzoxazole-2,2'-[2H,1'-benzopyran]): Place (0.28 mole) of 2-amino-4-phenylphenol and (0.28 mole) of propionic anhydride in a 250-milliliter roundbottom flask and heat on a steam bath for two hours. The mixture then is heated to drive oif the water and ammonia, and the residue is distilled at atmospheric pressure to yield a light-yellow oil with a boiling point of 150 to 165 degrees centigrade/l mm. Hg, which is 5- phenyl-Z-ethylbenzoxazole. The compound thus prepared is placed in a -milliliter round-bottom flask, and (0.17 mole) of methyl-p-toluene sulfonate is added. The mixture is heated at to degrees centigrade for two hours and allowed to cool to room temperature. The resultant light-yellow solid is washed several times with acetone to yield the second intermediate, S-phenyl-Z-ethylbenzoxazole methyl-p-toluene sulfonate.

Next, in a 50-milliliter round-bottom flask are placed (0.015 mole) of 5-phenyl-2-ethyl-benzoxazole methyl-ptoluene sulfonate, the second intermediate, and (0.015 mole) of 3-methoxy-5-nitrosalicylaldehyde, 25 milliliters of pyridine as a solvent, and 1 milliliter of piperidine as a catalyst. The solution is heated on a steam bath for one hour and cooled, and the resulting precipitate is removed by filtration, which precipitate is recrystallized several times from ethanol, yielding light-yellow crystals of 3,3'-dimethyl-5-phenyl-6-nitro-8-methoxy-spiro-(benzoXazo1e-2,2'-[2H,1-benzopyran]), the desired compound.

Example XIII Preparation of 3-methyl-3-ethyl-6'-nitro-spiro-(benz- 0xazole-2,2'-[2H,1'-benzopyran])2 Place (0.28 mole) of o-aminophenol and (0.28 mole) of n-butyric anhydride in a 250-milliliter round-bottom flask and heat on a steam bath for two hours. The mixture then is heated to drive off the Water and ammonia, and the residue is distilled at atmospheric pressure to yield a light-yellow oil with a boiling point of 220 to 232 degrees centigrade, which is Z-(n-propyl)-benzoxazole. The compound thus prepared is placed in a 100-milliliter round-bottom flask, and (0.17 mole) of methyl-p-toluene sulfonate is added. The mixture is heated at 140 to 155 degrees centigrade for two hours and allowed to cool to room temperature. The resultant light-yellow solid is washed several times with acetone to yield the second intermediate, 2-(n-propyl)-benzoxazole methyl-p-toluene sulfonate.

Next, in a 50-milliliter round-bottom flask are placed (0.015 mole) of 2-(n-propyl)-benzoxazole methyl-p-toluene sulfonate, the second intermediate, and (0.015 mole) of S-nitrosalicylaldehyde, 25 milliliters of pyridine as a solvent, and 1 milliliter of piperidine as a catalyst. The solution is heated on a steam bath for one hour and cooled, and the resulting precipitate is removed by filtration, which precipitate is recrystallized several times from ethanol, yielding light-yellow crystals of 3-methyl-3- ethyl 6' nitro spiro (benzoxazole 2,2 [2H,1- benzopyran] the desired compound.

What is claimed is:

The 3,3 dimethyl 6' nitro-spiro-(benzoxazole-2,2'- [2-H,1-benzopyran]) compound having the formula:

References (Tired in the file of this patent FOREIGN PATENTS Norway Sept. 16, 1961 OTHER REFERENCES UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No,v 3,149, 120 September 15, 1964 Elliot Berman et a1 It is hereby certified that error appears in the above numbered patent requiring correction and that the said Letters Patent should read as corrected belo* Column 2, line 29, for "Serail" read Serial column 3, line 34, for "methly" read methyl line 74, strike out the parenthesis, first occurrence, and insert instead a comma; same line 74, after "mole" insert a. closing parenthesis; column 5, line 48, for "centrigrade" read centigrade column 6, line 21, for "benzoaxazole" read benzoxazole Signed and sealed this 12th day of January 1965.

(SEAL) v y Attest:

ERNEST W. SWIDER' EDWARD J. BRENNER Attesting Officer Commissioner of Patents UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,149,120 September 15, 1964 Elliot Berman et a1,

It is hereby certified that error appears in the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

Column 2, line 29, for "Serail" read Serial column 3, line 34, for "methly" read methyl line 74, strike out the parenthesis, first occurrence, and insert instead a comma; same line 74, after mole" insert a closing parenthesis; column 5, line 48, for "ce'ntrigrade" read Centigrade column 6, line 21, for "benzoaxazole" read benzoxazole Signed and sealed this 12th day of January 1965,

( SEAL) r Attest: V

ERNEST W. SWIDER- EDWARD J. BRENNER Attesting Officer Commissioner of Patents