Eli Lilly and Company

Charles W Ryan

William B Blanchard

Bruce A Slomski

Samuel James Dominianni

Billy G Jackson

The present invention provides a process for preparing a novel intermediate for nizatidine.

Synthesis of nizatidine intermediate

A 4-acyl-o-phenylenediamine is selectively sulfonated on the amino group meta to the acyl group to provide an important intermediate for benzimidazole pharmaceuticals. Some of the intermediates are new to organic chemistry.

3-sulfonylamino-4-amino phenyl acyl derivatives

N-methyl-S-methyl-N'-[2-(2-dimethylaminomethylthiazol-4-ylmethylthio)ethyl] isothiourea is prepared by the reaction of 2-dimethylaminomethyl-4-(2-aminoethyl)thiomethylthiazole with methylcarbonimidodithioic acid, dimethyl ester, and is a useful intermediate for the preparation of nizatidine, a pharmaceutically valuable H.sub.2 -receptor inhibitor.

Isothiourea synthesis process

A stereo-selective preparation of novel sulfonated o-phenylenediamines carrying a trans-.alpha.-alkylidenebenzyl group at the 5-position, which are intermediates in the synthesis of antiviral benzimidazoles.

Synthesis of alkylidene intermediates

Reaction of an O-methyl or O-ethyl resorcinol with a cyclohexene carbinol derivative in the presence of a catalyst affords a 6a,10a-trans-1-methoxy or 1-ethoxy-6,6-dimethyl-6,6a,7,8,10,10a-hexahydro-9H-dibenzo[b,d]pyran-9-one derivative.

Preparation of 6a,10a-trans-hexahydrodibenzopyranones

Reaction of 4-(1-hydroxy-1-methylethyl)-3-cyclohexen-1-one with a 5-substituted resorcinol in the presence of boron tribromide, boron trifluoride or stannic chloride provides, depending upon the duration of reaction, either a 2,7-dihydroxy-5-isopropylidene-9-substituted-2,6-methano-3,4,5,6-tetrahydr o-2H-1-benzoxocin or a 6a,10a-cis-1-hydroxy-3-substituted-6,6-dimethyl-6,6a,7,8,10,10a-hexahydro- 9H-dibenzo[b,d]pyran-9-one.

Preparation of cis-hexahydrodibenzopyranones

Novel 2-oxy-5-isopropylidene-7-hydroxy-9-substituted-2,6-methano-3,4,5,6-tetrahy dro-2H-1-benzoxocins are prepared by condensing a 5-(substituted)resorcinol with a 1-alkoxy-4-(1-hydroxy-1-methylethyl)-1,4-cyclohexadiene in the presence of a suitable catalyst. The new benzoxocin derivatives are useful in the synthesis of certain dibenzo[b,d]pyran-9-ones, valuable as anti-anxiety, analgesic, and anti-depressant drugs.

2,6-Methano-2H-1-benzoxocins

Reaction of a 5-substituted resorcinol with a ketal of 4-(1-hydroxy)-1-methylethyl)-3-cyclohexen-1-one in the presence of a suitable catalyst effects condensation to provide substantially exclusively a cis-1-hydroxy-3-substituted-6,6-dimethyl-6,6a,7,8,10,10a-hexahydro-9H-dibe nzo[b,d]pyran-9-one.

Preparation of

2,6-Dimethoxyphenol reacts with a tertiary carbinol in the presence of an acid to provide exclusively a 1-hydroxy-2,6-dimethoxy-4-(tertiary alkyl)benzene, which when reacted with a halogenated disubstituted phosphite affords a 2,6-dimethoxy-4-(tertiary alkyl)phenyl disubstituted phosphate. Reduction of the phenyl phosphate derivative by reaction with an alkali metal affords a 1-(tertiary alkyl)-3,5-dimethoxybenzene, which upon reaction with a demethylating agent provides a 5-(tertiary alkyl)resorcinol.

Intermediates for 5-(tertiary alkyl) resorcinol preparation

Reaction of a 5-substituted resorcinol with a 1-alkoxy-4-(1-hydroxy-1-methylethyl)-1,4-cyclohexadiene in the presence of a catalyst such as boron tribromide, boron trifluoride or stannic chloride, and in the presence of about an equimolar quantity of water, affords predominantly a cis-hexahydrodibenzopyranone in high yields.

Process for preparing cis-hexahydrodibenzopyranones

Reaction of a 5-substituted resorcinol with a ketal of 4-(1-hydroxy-1-methylethyl)-3-cyclohexen-1-one in the presence of a suitable catalyst effects condensation to provide substantially exclusively a cis-1-hydroxy-3-substituted-6,6-dimethyl-6,6a,7,8,10,10a-hexahydro-9H-dibe nzo-[b,d]pyran-9-one.

2,6-Dimethoxyphenol reacts with a tertiary carbinol in the presence of an acid to provide exclusively a 1-hydroxy-2,6-dimethoxy-4-tertiary alkyl)benzene, which when reacted with a halogenated disubstituted phosphite affords a 2,6-dimethoxy-4-tertiary alkyl)phenyl disubstituted phosphate. Reduction of the phenyl phosphate derivative by reaction with an alkali metal affords a 1-(tertiary alkyl)-3,5-dimethoxybenzene, which upon reaction with a demethylating agent provides a 5-(tertiary alkyl)resorcinol.

5-(Tertiary alkyl) resorcinol preparation and intermediates therefor

Reaction of a 5-substituted resorcinol with a ketal of 4-(1-hydroxy-1-methylethyl)-3-cyclohexen-1-one in the presence of a suitable catalyst effects condensation to provide substantially exclusively a cis-1-hydroxy-3-substituted-6-6-dimethyl-6,6a,7,8,10,10a-hexahydro-9H-dibe nzo[b,d]pyran-9-one.

Reaction of an aluminum halide with a 2,7-dihydroxy-5-isopropylidene-9-substituted-2,6-methano-3,4,5,6-tetrahydr o-2H-1-benzoxocin in an organic solvent effects cleavage of the pyran ring system with concomitant recyclization to provide exclusively a trans-1-hydroxy-3-substituted-6,6-dimethyl-6,6a,7,8,10,10a-hexahydro-9H-di benzo[b,d]pyran-9-one.

Process for converting

Reaction of cis-1-hydroxy-3-substituted-6,6-dimethyl-6,6a,7,8,10,10a-hexahydro-9H-dibe nzo[b,d]pyran-9-ones with an aluminum halide in an unreactive organic solvent effects complete epimerization to provide the corresponding trans-1-hydroxy-3-substituted-6,6-dimethyl-6,6a,7,8,10,10a-hexahydro-9H-di benzo[b,d]pyran-9-one.

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Indianapolis, IN, United States of America

Charles W Ryan