HU176770B - Process for preparing etheno-anthracene derivatives - Google Patents

Abstract

1470899 Bridged-ring anthracene derivatives E I DU PONT DE NEMOURS & CO 20 Nov 1974 [21 Nov 1973 30 Sept 1974] 50318/74 Heading C2C The invention comprises compounds of the formula where R<SP>1</SP> and K<SP>2</SP> are H, C 1 -C 4 alkyl, C 1 -C 4 perfluoroalkyl, halogen, C 1 -C 4 alkoxy, C 1 -C 4 alkylthio, C 1 -C 4 perfluoroalkylthio, C 1 -C 4 acyl, C 1 -C 4 alkylsulphonyl, C 1 -C 4 perfluoroalkylsulphonyl, di(C 1 -C 4 alkyl)aminosulphonyl, sulphamyl, amino, C 1 -C 4 alkylamino, di(C 1 - C 4 alkyl) amino, X is a linear chain of 3 atoms which contains a central atom of nitrogen, the remaining atoms being carbon substituted with hydrogen, or up to one oxygen to form carbonyl and said central atom of nitrogen is doubly bonded to one of said carbon atoms or is substituted with H, C 1 -C 12 alkyl, alkenyl of up to 4 carbon atoms attached to N by a saturated carbon atom, cycloalkyl or cycloalkenyl of 3-9 carbon atoms, cycloalkyl (C 1 -C 4 ) alkyl, cycloalkenyl (C 1 -C 4 ) alkyl, adamantylmethyl, α-furylmethyl, α-thiophenylmethyl or phenyl- (C 1 -C 4 ) alkyl and acid addition salts thereof. The compounds may be prepared by heating compounds of the formula

Description

The present invention relates to a process for the preparation of novel 9,12-ethenanthracene derivatives wherein the etheno group bridging group contains nitrogen.

9,10-Ethano-anthracene derivatives without a bridging group are known, and certain ethanol-anthracene derivatives bearing a 9- and 12-position bridging group are also described in the literature (Meek et al., J. Am. Chem. Soc., 74). , 761 (1952); 78, 5413 (1956); 82, 2566 (1960); Alder and Heimbach (1953) Chem. Ber. 86, 1312; and British Patent No. 1,266,890). However, it is known that ethanol anthracene of formula V can be prepared in a low yield by an internal (intramolecular) Diels-Alder reaction [Meek and Dann, J. Org. Chem., 21, 968 (1956)].

It has now been found that the novel compounds of formula I wherein

R ¹ and R ² are hydrogen, halogen or lower alkyl and may be different or the same, provided that one of R ^{1 *} and R ² is always hydrogen,

X is a straight chain of 3 atoms containing one central nitrogen atom in which the other two atoms are carbon atoms attached to hydrogen atoms or up to one oxygen atom and where the central nitrogen atom is a lower 2-alkenyl bonded through a hydrogen atom containing up to 12 carbon atoms Substituted with C3-C9-cycloalkyl, cycloalkyl-lower alkyl, cycloalkenyl-lower alkyl, phenyl-lower alkyl, adamantylmethyl, benzyl, or β-phenylethyl , with the proviso that X-free carbon - carbon double bond - can be used as inhibitors for the free radical polymerization of vinyl compounds.

Preferred compounds are those compounds of formula I wherein X is a group of formula IV wherein R ^{5 is} hydrogen, alkyl of up to 12 carbon atoms (particularly preferably lower alkyl), cycloalkylmethyl of 4 to 10 carbon atoms, and R one of R ² and R ² is halogen and the other is hydrogen.

In addition to their usefulness as inhibitors, certain compounds of Formula I, namely the amines of Formula I, are rearranged in the presence of an acidic catalyst to dihydromethano-dibenzocycloheptapyrroles, which may be reduced by the method described in U.S. Patent No. 4,468,686. The amides or lactams of formula I are rearranged to dibromo-dihydromethano-dibenzocycloheptapyrroleones by treatment with bromine in a solvent such as methylene chloride. Elemental bromine can then be removed and the resulting tetra hydro derivatives reduced by the resulting lactam. Many of the latter compounds are useful as tranquilizers in warm-blooded animals.

Compounds of formula I are numbered as depicted in formula II.

The compounds of formula I according to the invention can be prepared from the alkynyl anthracene derivatives of formula III wherein X, R ¹ and R ² are as defined above by an internal Diels-Alder reaction. (Schematic diagram.)

This is done by heating an alkynyl anthracene derivative of the Formula III alone or in an inert solvent, preferably an aromatic hydrocarbon, depending on the type of atoms in the X chain and the nature of the substituents R ¹ and R ² at 80 ° C and 250 ° C. temperature. The reaction time is preferably from 1 hour to 48 hours.

The alkynyl anthracene derivatives of Formula III may be prepared as shown in Scheme B. In this scheme, a 9-anthaldehyde derivative is reacted with a suitable amine in an alcohol at a temperature of 25 ° C to 150 ° C to give an imine derivative. The latter compound is then reduced with a metal hydride such as sodium borohydride or sodium cyanoborohydride in an alcohol such as methanol, ethanol or isopropanol (the alcohol used for the reduction may be the same as the alcohol used to make the imine). C to 100 ° C. The secondary amine thus formed is then condensed with a propargyl halide, preferably propargyl bromide, at a temperature of from 0 ° C to 100 ° C, preferably at room temperature, in the presence of an inorganic base such as an aqueous alkali metal carbonate solution or reaction with propargyl bromide. Such organic bases include spatially inhibited amines such as diisopropylethylamine.

The resulting alkynyl anthracene derivatives of formula III can then be cyclized to compounds of formula I as described above.

Compounds of formula I (i.e., compounds of formula Ia) containing a hydrogen atom in the X chain as a substituent R ⁵ may be prepared by reacting a 9-anthaldehyde derivative with propargylamine in ethanol at 25-150 ° C. described subsequently reduced and cyclized 0-100 ³ C ethanolic solution of sodium cyano borohydride. Alternatively, the reduction may be carried out prior to the cyclization.

Thus, compounds of formula Ia are obtained which can then be alkylated or acylated to introduce various R ⁵ substituents on the nitrogen atom. The acyl groups can then be reduced to the corresponding alkyl groups.

The compounds of formula III may also be prepared by reacting a 9-halomethyl anthracene derivative, preferably a 9-chloromethyl anthracene derivative, in an inert solvent at room temperature to 150 ° C with an amine of formula R ⁵ NH _2. The resulting secondary amino substituted anthracene derivative is reacted with a propargyl halide, preferably propargyl bromide, as described above.

Further methods for preparing certain specific compounds can be found in the Examples.

The following examples will illustrate the invention in greater detail.

Example 1

3,5-Dihydro-5,9b- (o, e) -dibenzoisoindol-1 (2H) -one (Scheme C)

A mixture of 18.85 g of 9-anthroic acid and 60 ml of thionyl chloride was refluxed for 1 hour, then excess thionyl chloride was removed in vacuo (30 mmHg, 90 ° C bath temperature), and toluene (50 ml) was added to the residue. the reaction mixture was concentrated again. This operation is then repeated once more to give 20.6 g of 9-anthroyl chloride in the form of a highly moisture-sensitive, yellow precipitate.

To a solution of propargylamine (g) in tetrahydrofuran (60 ml) was added a solution of 9-anthroyl chloride (13.68 g) in tetrahydrofuran (30 ml) at 10-15 ° C, and the resulting mixture was stirred at room temperature for 4 hours and the solvent was evaporated. The residue was dissolved in methylene chloride and the organic layer was washed with 5% aqueous sodium bicarbonate solution, dried and evaporated to give crude N-propargyl-9-anthramide (14.54 g). An analytically pure sample recrystallized from ethanol has a melting point of 201-202 ° C.

Nuclear Magnetic Resonance Spectrum (NMR) spectra are defined as follows:

s = szingulctt; d, doublet; t = triplet; q kvadruplctt; m = multiplet.

τ 1.5-2.8 (m, 9); 3.7 (broad, 1); 5.7 (d of d, 2) and

7.7 (t, 2.5 Hz, 1).

Analysis calculated for C ₁₈ H ₁₃ NO: C, 83.87; H, 5.05; N, 5.40. Found: C, 83.50; H, 5.08; N, 5.29.

A mixture of crude N-propargyl-9-anthramide (g) and p-xylene (200 ml) was refluxed overnight, then the solvent was distilled off and the residue was sublimated at 200-210 ° C (0.5 micron). Crystallization of the sublimate from 110 ml of acetonitrile afforded 4.7 g of the title compound, m.p. 264-265 ° C (unchanged during recrystallization). Nuclear Magnetic Resonance Spectrum: τ 2.3-3.3 (m, 10); 4.8 (d, J = 6Hz, 1) and 5.9 (d, J = 2Hz, 2).

Calcd for C] ₈ H ₁₃ NO: Calculated: C% = 83.37, H% = 5.05, N% = 5.40; Found: C, 83.19; H, 5.11; N, 5.40.

Example 2

2-Methyl-3,5-dihydro-5,9b- (o, e) -dibenzoisoindol-1 (2H) -one (Scheme D)

In the same manner as in Example 1, N-methylpropargyl amine was used instead of propargyl amine to give N-methyl-N-propargyl-9-anthramide first as an oil and then to give the solid title compound. N-methyl-N-propargyl-9-anthramide NMR:

τ 1.7-2.9 (m, 9); 5.4 (d, 2.5 Hz, 1.3); 6.4 (d, 2.5 Hz, 0.7); 6.7 (s, 0.9); 7.4 (s, 2.1); 7.7 (t, 2.5 Hz, 0.7) and 8.0 (t, 0.3). There are two rotamers in the spectrum.

Identification of the title compound:

Nuclear Magnetic Resonance Spectrum: τ 2.3-3.3 (m, 9); 4.8 (d, J = 6Hz, 1);

5.9 (d, J = 2Hz, 2) and 6.9 (s, 3).

Melting point: 250-255 ° C.

Calcd for C _I9 H ₁₅ NO Calculated: C% = 83.49, H% = 5.53, N% = 5.13; Found: C, 83.84; H, 5.66; N, 5.10.

Example 3

3.5- Dihydro-5,9b- (o, e) -dibenzoisoindole (Scheme E)

A mixture of 9-fortnyl anthracene (16.7 g), propargylamine (5 g) and ethanol (100 ml) was refluxed for 1 hour, the solvent removed and the residue crystallized from acetonitrile (100 ml) to give 16.1 g (82%) of m.p. 143-144 ° C, yielding N-propargyl-9-anthracenemethylimine.

Nuclear Magnetic Resonance Spectrum: τ 0.2 (t, 2Hz, 1); 1.7-3.0 (m, 9);

5.1 (t, 2Hz, 2) and 7.3 (t, 2Hz, 1).

Calcd for C ₁₈ H, _B N O: Calculated: C% = 88.86, H% = 5.39, N% = 5.76; Found: C, 88.83; H, 5.56; N, 5.87.

A mixture of 19.4 g of crude N-propargyl-9-anthracenemethylenimine and 200 ml of p-xylene is refluxed for 3 hours and then cooled to give 14.6 g of the title compound, m.p. 212-214 ° C. An additional 1.4 g of product can be isolated by evaporation of the mother liquor and crystallization of the residue from 50 ml of acetonitrile.

Nuclear Magnetic Resonance Spectrum: τ 1.1 (m, 1); 2.5-3.5 (m, 9); 4.8 (d, J = 6Hz, 1) and 5.4 (t, J = 2Hz, 2).

Calcd for C ₁₈ H ₁₃ N O: Calculated: C% = 88.86, H% = 5.39, N% = 5.76; Found: C, 89.10; H, 5.58; N, 5.66.

The title compound can also be prepared directly by heating 9-formyl anthracene and propargylamine in p-xylene.

Example 4

1.2.3.5- Tetrahydro-5,9b- (o, e) -dibenzoisoindole (Scheme F)

To a suspension of 10.19 g of 3,5-dihydro-5,9b- (o, e) -dibenzoisoindole in 50 ml of methanol and 10 ml of acetic acid is slowly added 4.70 g of sodium cyanoborohydride under cooling. After stirring at room temperature overnight, the unreacted metal hydride was quenched by the addition of concentrated hydrochloric acid in an ice bath, made basic and extracted with methylene chloride. After drying, the extract was concentrated to give the title compound as a slowly solidifying oil (10.49 g).

Nuclear Magnetic Resonance Spectrum: τ 2.6-3.7 (m, 9); 4.9 (d, 6Hz, 1); 6.0 (s, 2); 6.5 (d, 2Hz, 2) and 7.5 (s, 1).

After crystallization from isopropanol, the hydrochloride of the product melts at 273 DEG C. with decomposition.

Example 5

2-Methyl-1,2,3,5-tetrahydro-5,9b- (o, e) dibenzoisoindole (Scheme G)

A mixture of 8.19 g of 3,5-dihydro-5,9b- (o, e) -dibenzoisoindole, 25 ml of formic acid and 25 ml of aqueous formaldehyde solution is refluxed for 3 hours and then 10 ml of concentrated hydrochloric acid are added. We are added. The volatiles were removed and the residue was stirred with aqueous sodium hydroxide and methylene chloride. The dried methylene chloride extract was evaporated and the residue crystallized from acetonitrile to give 5.04 g (58%) of the title compound in two portions, m.p. 196-197 ° C.

Nuclear Magnetic Resonance Spectrum: τ 2.4-3.1 (m, 8); 3.3 (d of 6, J = 6 / 2Hz, 1); 4.8 (d, 6Hz, 1); 6.1 (s, 2); 6.6 (d, 2Hz, 2) and 7.3 (s, 3).

Analysis calculated for C ₁₉ H ₁₇ N: C, 87.99; H, 6.61; N, 5.40; Found: C, 88.05; H, 6.91; N, 5.32.

The title compound may also be prepared by reacting 1,2,3,5-tetrahydro-5,9b- (o, e) -dibenzoisoindole under the same conditions with formaldehyde and formic acid.

Example 6

2-Cyclopentylmethyl-1,2,3,5-tetrahydro-5,9b- (o, e) -dibenzoisoindole (Scheme H)

A mixture of 43.5 g of 9-formyl anthracene, 20.97 g of cyclopentylmethylamine and 150 ml of ethanol is heated under reflux for 1.5 hours, and the resulting solution of N-cyclopentylmethyl-9-anthracenemethylenimine is heated to 60 ° C. After cooling, 8.2 g of sodium borohydride are added in small portions while maintaining the temperature at 55-60 ° C. After stirring for a further 1.5 hours, 35 ml of concentrated hydrochloric acid were added under cooling and stirring was continued for 0.5 hours. The reaction mixture was then basified and extracted with methylene chloride. After drying the extract, the solvent was evaporated to give 59.1 g of N-cyclopentylmethyl-9-anthracenemethylamine as an oil.

Nuclear Magnetic Resonance Spectrum: τ1.8-3.1 (m, 9); 5.6 (s, 2); 7.5 (d, 7Hz, 2) and 7.8-9.3 (m, 10).

Under a nitrogen atmosphere, a mixture of 63.5 g of N-cyclopentyl-9-anthracenemethylamine, 50 g of propargyl bromide, 200 ml of methylene chloride and 200 ml of a 10% aqueous potassium carbonate solution is stirred vigorously for 2 hours and the phases are separated. the aqueous phase was extracted once more with methylene chloride. The combined organic phases were then evaporated to give 63.5 g of N-cyclopentylmethyl-N-propargyl-9-anthracenemethylamine as an oil.

Nuclear Magnetic Resonance Spectrum: τ2.3-3.0 (m, 9); 5.5 (s, 2); 6.8 (d,

2.5 Hz, 2); 7.5 (m, 2); 7.7 (t, 2.5 Hz, 1) and 7.5-9.2 (m, 9).

This product was then cyclized under reflux in toluene (200 mL) for 1.25 hours. Distillation of the toluene and crystallization of the residue from 150 ml of isopropanol gave 44.4 g of the title compound having the same infrared and nuclear magnetic resonance spectra as 1,2,3,5-tetrahydro-5,9b- (o, e) -. acylation of dibenzoisoindole with cyclopentanecarbonyl chloride followed by reduction of the resulting compound with appropriate spectral data.

Proceeding as described above, using the appropriate amine and substituted 9-anthaldehyde instead of cyclopentylmethylamine, the following 2-substituted-1,2,3,5-tetrahydro-5,9- (o, e) ) -Dibenzoisoindole derivatives may be prepared: 2-cyclopropyl-1,2,3,5-tetrahydro-5,9b- (o, e) -dibenzoisoindole, m.p. 109-110 ° C.

Calcd for C _{2 H]} N ₉ O: C ° / _o = 88.38, H% = 6.71, N% = 4.91; Found: C, 88.21; H, 6.68; N, 5.06;

2-cyclohexyl-1,2,3,5-tetrahydro-5,9- (o, e) -dibenzoisoindole, m.p. 152-154 ° C.

Calcd for C ₂₄ H ₂₅ N O: Calculated: C% = 88.03, H% = 7.70, N% = 4.28; Found: C, 87.82; H, 7.77; N, 4.35;

2-Benzyl-1,2,3,5-tetrachydro-5,9b- (o, e) -dibenzoisoindole, which has the same NMR spectrum as 1,2,3,5-tetrahydro-5,9b- Benzoylation of (o, e) -dibenzoisoindole followed by reduction of the compound thus obtained with 8-chloro-2-cyclohexylmethyl-1,2,3,5-tetrahydro-5,9b- (o, e). m.p. 144-146 ° C) -dibenzoisoindole.

Calcd for C ₂₅ H _{2 (CIN} O: Calculated: C% = 79.87, H% = 6.97, N% = 3.73 Found% C = 79.74, H = 7.09% N, 3.66.

Example 7

2-Cyclopropylmethyl-1,2,3,5-tetrahydro-5,9b- (o, e) -dibenzoisoindole (Scheme I)

To a suspension of 3.75 g, 2,3,5-tetrahydro-5,9b- (o, e) -dibenzoisoindole and 3 g of magnesium oxide in 20 ml of anhydrous tetrahydrofuran are added slowly 2.4 g of cyclopropanecarbonyl chloride in 5 ml of tetrahydrofuran The reaction mixture was stirred at room temperature for 5 hours, filtered and the filtrate was evaporated. The residue was taken up in methylene chloride, and the resulting solution was washed with aqueous sodium bicarbonate solution and dried. Evaporation of the solvent afforded 4.07 g of crude 2-cyclopropylcarbonyl-1,2,3,5-tetrahydro-5,9b- (o.e) -dibenzoisoindole which could be used in the next step without further purification.

A sample which is doubly crystallized from isopropanol has a melting point of 171-173 ° C.

Analysis calculated for C ₂₂ H ₁₉ NO: C, 84.31; H, 6.11; N, 4.47. Found: C, 84.41; H, 6.31; N, 4.88.

A mixture of 9.87 g of crude 2-cyclopropylcarbonyl-1,2,3,5-tetrahydro-5,9b- (o, e) -dibenzoisoindole, 4.83 g of lithium aluminum hydride and 100 ml of tetrahydrofuran is used under reflux. Reflux for 2 hours and then cool. The cooled mixture was washed successively with 4.8 ml of water, 4.8 ml of 15% sodium hydroxide solution and 14.4 ml of water, then filtered and evaporated to give crude 2-cyclopropylmethyl (9.29 g). -1,2,3,5-tetrahydro-5.9b- (o, e) -dibenzoisoindole is obtained, m.p. 109-110 ° C after single crystallization from isopropanol.

Nuclear Magnetic Resonance Spectrum: τ2.5-3.5 (m, 9); 4.8 (d, 6 Hz, 1);

6.1 (s, 2); 6.5 (d, 2 Hz, 2); 7.3 (d, 6Hz, 2) and 8.7-9.8 (m, 5).

Calcd for C ₂₂ H _2] N O: Calculated: C ° / _O = 88.25, H ° / _O = 7.07, N% = 4.68; Found: C, 87.87; H, _O = 7.35; N, 4.70.

In the same manner as in Example 7, but using appropriately substituted carbonyl chlorides instead of cyclopropanecarbonyl chloride, the following 2-substituted-1,2,3,5-tetrahydro-5,9b- (o, e) -dibenzoisoindole derivatives were obtained. we can produce. The NMR spectra of each compound show signs of the 1,2,3,5-tetrahydro-5,9b- (o, e) -dibenzoisoindole system [τ2.6-

3.2 (m, 2); 3.4-3.5 (d / t, 6/2 Hz, 1); 4.6-5.0 (d, 6Hz, 1); 6.0-6.3 (s, 2) and 6.6-6.8 (d, 2Hz, 2)], depending on the chemical nature of the 2-position substituent.

For each listed compound, additional signals due to the presence of the 2-position substituent are given.

2-ethyl-1,2,3,5-tetrahydro-5,9b- (o, e) -dibenzoisoindole, NMR: τ7.3 (q, 7 Hz, 2) and 8.7 (t, Ί Hz, 3);

2-isobutyl-1,2,3,5-tetrahydro-5,9b- (o, e) -dibenzoisoindole, NMR: τ7.6 (d, 7 Hz, 2); 7.7-8.5 (m, 1) and 9.0 (d, 7 Hz, 6);

2-neopentyl-1,2,3,5-tetrahydro-5,9b- (o, e) -dibenzoisoindole, NMR: δ7.5 (s, 2) and 9.0 (s, 9);

2-cyclobutylmethyl-1,2,3,5-tetrahydro-5,9b- (o, e) -dibenzoisoindole, NMR: δ7.1-8.5 (t, 9);

2-Cyclopentylmethyl-1,2,3,5-tetrahydro-5,9b- (o, e) -dibenzoisoindole, m.p. 110-111 ° C.

Nuclear Magnetic Resonance Spectrum: τ7.3-9.0 (m, 11).

Analysis: Calculated for C ₂₄ H _{2 J} N: C, 88.03; H, _O = 7.70; N, 4.28; Found: C, 87.68; H, 7.75; N, 4.43.

5-methyl-2-cyclohexylmethyl-1,2,3,5-tetrahydro-5,9b- (o, e) -dibenzoisoindole, NMR: τ3.9 (t, 2 Hz, 1) (proton C —4; no signal between 4.6 and 5.0); 7.6 (d, 6 Hz, 2); 7.9 (s, 3) and 8.0-9.5 (m, 11);

2- (2-cyclohexylethyl) -1,2,3,5-tetrahydro-5,9b- (o, e) -dibenzoisoindole, NMR: δ7.1-9.5 (m, 15) ;

2- (? ^3- cyclohexenylmethyl) -1,2,3,5-tetrahydro-5,9b- (o, e) -dibenzoisoindole, NMR: τ4.3 (m, 2);

7.5-9.0 (m, 99);

2-Cycloheptymethyl-1,2,3,5-tetrahydro-5,9b- (o, e) -dibenzoisoindole, NMR: δ7.5-9.2 (m, 15);

2-benzyl-1,2,3,5-tetrahydro-5,9b- (o, e) -dibenzoisoindole, NMR: τ2.4-3.0 (m, 5) and 6.3 (s) , 2);

2- (1 -adamantylmethyl) -1,2,3,5-tetrahydro-5,9b- (o, e) -dibenzoisoolidol, NMR: τ7.6 (s, 2); 7.5 and

8.5 (m, 15);

2- (2-phenylethyl) -1,2,3,5-tetrahydro-5,9b- (o, e) -dibenzoisoindole, NMR: τ2.6-3.1 (m, 5) and 7.0 (s, 4);

2-methyl-8-chloro-1,2,3,5-tetrahydro-5,9b- (o, e) -dibenzoisoindole, NMR: τ7.5 (s, 3), instead of 8 aromatic protons ; and

2-allyl-1,2,3,5-tetrahydro-5,9b- (o, e) -dibenzoisoindole, NMR: τ3.7-4.3 (m, 1); 4.5-5.0 (m, 2) and

6.7 (d, 2).

Example 8

2-Cyclohexylmethyl-1,2,3,5-tetrahydro-5,9b- (o, e) dibenzoisoindole (Scheme J)

In the same manner as in Example 7, but using cyclohexanecarbonyl chloride, instead of cyclopropanecarbonyl chloride, 2-cyclohexanecarbonyl-1,2,3,5-tetrahydro-5,9b- (o, e) -dibenzo-, m.p. isoindole is obtained.

Calcd for C ₂₅ H ₂₅ NO calculated: 84.47% C, 7.09% N, 3.94;

Found: C, 84.36; H, 7.05; N, 4.00.

This compound was also reduced as described in Example 7 to give the title compound, mp 157-158 ° C. Nuclear Magnetic Resonance Spectrum: τ2.5-3.5 (m, 9); 4.9 (d, 2 Hz, 2); 7.5 (d, 6Hz, 2) and 7.7-9.5 (m, 11).

Calcd for C ₂₅ H ₂₇ N O: Calculated: C% = 87.93, H% = 7.97, N% = 4.10; Found: C, 87.80; H, 7.66; N, 4.29.

2-Chloro-9-anthaldehyde and

2,6-Dimethoxy-9-anthaldehyde can be used as starting material as described in Examples 3 and 6 to give the appropriately substituted compounds of Formula I.

The following substituted 9-anthronic acids, also known in the art, can be used as starting materials for the preparation of the corresponding compounds of formula I as described in Examples 1 and 2: 1-chloro-9-anthroic acid, 2-chloro-9-anthroic acid, 1,5-dichloro -9-anthanoic acid, 2-methyl-9-anthanoic acid, 3-chloro-9-anthanoic acid, 1,4-dichloro-9-anthanoic acid, 2,5-dichloro-9-anthanoic acid and 4,5-dichloro-9-anthronic acid .

As mentioned above, the compounds of Formula I of the present invention can be used as polymerization inhibitors for free radical polymerization of vinyl compounds. Their suitability for this purpose is demonstrated by demonstrating the inhibitory effect on acrylonitrile polymerization.

Example 9

0.5 ml of distilled acrylonitrile, 2 ml of toluene, 20 mg of azobis (isobutyronitrile) initiator and 2-methyl-3,5-dihydro-5,9b- (o, e) prepared in Example 2 were charged into a Carius tube. 70 mg of dibenzoisoindol-1 (2H) -one. The tube was degassed, sealed under vacuum and shaken at room temperature overnight. Polyacrylonitrile is thus not formed. In control experiments, under the same conditions but leaving the compound of Example 2, solid polyacrylonitrile is separated from the solution.

Under the same conditions, 2-methyl-1,2,3,5-tetrahydro-5,9- (o, e) -dibenzoisoindole, prepared as described in Example 5, also prevents the polymerization of acrylonitrile.

Claims (4)

Patent claims CLAIMS 1. A process for the preparation of the ethenanthracene derivatives of the general formula (I) R ¹ and R ² are hydrogen, halogen or lower alkyl and may be different or the same, with the proviso that one of R ¹ and R ³ is always hydrogen, X is a straight chain of 3 atoms containing one central nitrogen atom in which the other two atoms are carbon atoms attached to hydrogen atoms or at most one oxygen atom, and wherein the central nitrogen atom is alkyl of up to 12 carbon atoms, lower alkenyl bonded through nitrogen saturated carbon atoms. Substituted with 3 to 9 carbon atoms, cycloalkyl, cycloalkyl (lower) alkyl, cycloalkenyl (lower) alkyl, phenyl (lower) alkyl, adamantylmethyl, benzyl or β-phenylethyl, with the proviso that X is free of carbon-carbon double bond, characterized in that an alkynyl anthracene derivative of the Formula III, wherein X, R ¹ and R ² are as defined herein, alone or in an inert solvent Heat at a temperature of from C to 250 ° C. (Priority: September 30, 1974) 2. A process according to claim 1 wherein the starting material is a compound of formula III wherein R ¹ and R ² are as defined in claim 1 and are X-CH 2 -NR ⁵ -CH 2 -. and ^R5 is hydrogen, alkyl having up to 12 carbon atoms, cycloalkyl-methyl or benzyl group having 4-10 carbon atoms. (Priority: November 21, 1973) 3. The process according to claim 1 or 2, wherein the inert solvent is an aromatic hydrocarbon. (Priority: November 21, 1973) The process of claim 1 or 2, wherein the heating is carried out for a period of from 1 hour to 48 hours. (Priority: November 21, 1973)