{"id":{"repo_id":"cent-lancashire","oai_identifier":"oai:clok.uclan.ac.uk:20338"},"canonical_url":"https://search.dev.ndltd.org/etd/cent-lancashire/oai:clok.uclan.ac.uk:20338","repository":{"repo_id":"cent-lancashire","name":"University of Central Lancashire","base_url":"https://clok.uclan.ac.uk/cgi/oai2"},"display":{"title":"Some chemistry of bromobenzopyrans","abstract":"A series of 2,2-disubstituted chroman-4-ones has been prepared by the base catalysed condensation of a carbonyl compound with 2'-hydroxyacetophenone. Chroman-4-ones substituted in the aromatic ring were more conveniently prepared by the cyclocondensation of a phenol with an a,j3-unsaturated carboxylic acid. 2,4-Dimethylphenyl-3-methylbut-2-enoate was obtained as a by-product during the preparation of 2,2,6,8 tetramethylchroman-4-one from 2,4-dimethyiphenol and 3,3-dimethylacrylic acid in polyphosphoric acid. The ester in polyphosphoric acid underwent a Fries rearrangement to give the chroman-4-one, but in methanesulfonic acid it gave 3,4-dihydro-4,4,6,8-tetramethylcoumarin. Reduction and dehydration of the resulting chroman-4-ols gave the 2H-chromenes in excellent yield. Addition of N-bromosuccinimide in moist dimethyl sulfoxide to the 2H-chromenes gave the trans-3-bromochroman-4-ols in good yield. Subsequent dehydration using a catalytic amount of 4-toluenesulfonic acid in refluxing toluene afforded the 3-bromo-2H-chromenes. A novel bis-4-(3-bromochromanyl)ether was isolated from the dehydration of 3-bromo-2,2-dimethylchroman-4-ol. Its formation is thought to arise from intermolecular capture of the benzylic cation by a second molecule of the bromohydrin. 4-Bromo-2H-chromenes have been obtained in a single step and in excellent yield from the chroman-4-ones by reaction with phosphorus tribromide. A novel 2H-chromene-4-phosphonic acid was characterised from the reaction of 2,2-dimethylchroman-4-one with PBr3. Lithiation of the 4-bromo-2H-chromenes gave the 4-chromenyl lithium which reacted with a range of electrophiles to afford novel 4-substituted 2H-chromenes. However, lithiation of the isomeric 3-bromo-2H-chromenes did not lead to the corresponding 3-substituted 2H-chromenes but gave instead substituted 2'-hydroxyphenyl allenes in good yields. This method constitutes a new route to the allene system. Reactivity of the allenes towards bromination, hydroboration and cycloaddition reactions have been investigated. 3,4-Dibromo-2,2,6,8-tetramethyl-2H-chromene has been prepared by the bromination of 4.bromo-2,2,6,8-tetramethyl-2H-chromene. 3,4,7-Tribromo-2,2,6,8-tetramethyl- 2H-chromene was obtained as a by-product The reaction of 3,4-dibromo-2,2,6,8-tetramethyl-2H-chromene with alkyllithium reagents gave mainly the 4-ailcyl substituted 211-chromenes with trace amounts of the 4-unsubstituted 2H-chromenes. Reaction of 3,4-dibromo-2,2,6,8-tetramethyl-2H-chrOmene with magnesium in THF in the presence of furans gave the Diels-Alder adducts, as a result of the trapping of the heteroaryne, 3,4-didehydro-2H[ 1 ]ben zopyran. This reaction constitutes the generation of a novel aryne. Diels-Alder adducts obtained by the use of 2,5-dimethylfuran and 1,3-diphenylisobenzofuran have been aromatised providing facile access to dibenzo[bdjpyrans.","abstract_html":"A series of 2,2-disubstituted chroman-4-ones has been prepared by the base catalysed condensation of a carbonyl compound with 2'-hydroxyacetophenone. Chroman-4-ones substituted in the aromatic ring were more conveniently prepared by the cyclocondensation of a phenol with an a,j3-unsaturated carboxylic acid. 2,4-Dimethylphenyl-3-methylbut-2-enoate was obtained as a by-product during the preparation of 2,2,6,8 tetramethylchroman-4-one from 2,4-dimethyiphenol and 3,3-dimethylacrylic acid in polyphosphoric acid. The ester in polyphosphoric acid underwent a Fries rearrangement to give the chroman-4-one, but in methanesulfonic acid it gave 3,4-dihydro-4,4,6,8-tetramethylcoumarin. Reduction and dehydration of the resulting chroman-4-ols gave the 2H-chromenes in excellent yield. Addition of N-bromosuccinimide in moist dimethyl sulfoxide to the 2H-chromenes gave the trans-3-bromochroman-4-ols in good yield. Subsequent dehydration using a catalytic amount of 4-toluenesulfonic acid in refluxing toluene afforded the 3-bromo-2H-chromenes. A novel bis-4-(3-bromochromanyl)ether was isolated from the dehydration of 3-bromo-2,2-dimethylchroman-4-ol. Its formation is thought to arise from intermolecular capture of the benzylic cation by a second molecule of the bromohydrin. 4-Bromo-2H-chromenes have been obtained in a single step and in excellent yield from the chroman-4-ones by reaction with phosphorus tribromide. A novel 2H-chromene-4-phosphonic acid was characterised from the reaction of 2,2-dimethylchroman-4-one with PBr3. Lithiation of the 4-bromo-2H-chromenes gave the 4-chromenyl lithium which reacted with a range of electrophiles to afford novel 4-substituted 2H-chromenes. However, lithiation of the isomeric 3-bromo-2H-chromenes did not lead to the corresponding 3-substituted 2H-chromenes but gave instead substituted 2'-hydroxyphenyl allenes in good yields. This method constitutes a new route to the allene system. Reactivity of the allenes towards bromination, hydroboration and cycloaddition reactions have been investigated. 3,4-Dibromo-2,2,6,8-tetramethyl-2H-chromene has been prepared by the bromination of 4.bromo-2,2,6,8-tetramethyl-2H-chromene. 3,4,7-Tribromo-2,2,6,8-tetramethyl- 2H-chromene was obtained as a by-product The reaction of 3,4-dibromo-2,2,6,8-tetramethyl-2H-chromene with alkyllithium reagents gave mainly the 4-ailcyl substituted 211-chromenes with trace amounts of the 4-unsubstituted 2H-chromenes. Reaction of 3,4-dibromo-2,2,6,8-tetramethyl-2H-chrOmene with magnesium in THF in the presence of furans gave the Diels-Alder adducts, as a result of the trapping of the heteroaryne, 3,4-didehydro-2H[ 1 ]ben zopyran. This reaction constitutes the generation of a novel aryne. Diels-Alder adducts obtained by the use of 2,5-dimethylfuran and 1,3-diphenylisobenzofuran have been aromatised providing facile access to dibenzo[bdjpyrans.","abstract_has_math":false,"creators":["Rahman, Md. Moshfiqur"],"institution":"University of Central Lancashire","degree_name":"phd","degree_level":"doctoral","degree_discipline":null,"degree_department":null,"school":null,"contributors":[],"advisors":[],"committee_chairs":[],"committee_members":[],"year":1995,"date_issued":"1995-11","date_published":"1995-11","updated_at":"2026-07-24T01:36:10Z","subjects":["F100 - Chemistry"],"languages":["en"],"rights":[],"rights_urls":[],"identifier_entries":[]},"links":{"outbound_url":null,"outbound_label":null,"outbound_source":null},"metadata_groups":[{"id":"people","label":"People","entries":[{"key":"dc:creator","label":"Author","values":["Rahman, Md. Moshfiqur"]}]},{"id":"academic_context","label":"Academic Context","entries":[{"key":"dc:date","label":"Dc Date","values":["1995-11-01"]},{"key":"dc:date.issued","label":"Date","values":["1995-11"]},{"key":"dc:publisher.department","label":"Dc Publisher Department","values":["Chemistry"]},{"key":"dc:publisher.institution","label":"Dc Publisher Institution","values":["University of Central Lancashire"]},{"key":"dc:relation.isreferencedby","label":"Dc Relation Isreferencedby","values":["https://knowledge.lancashire.ac.uk/id/eprint/20338/"]},{"key":"dc:type","label":"Dc Type","values":["Thesis"]},{"key":"dc:type.qualificationlevel","label":"Dc Type Qualificationlevel","values":["doctoral"]},{"key":"dc:type.qualificationname","label":"Dc Type Qualificationname","values":["phd"]}]},{"id":"subjects_keywords","label":"Subjects and Keywords","entries":[{"key":"dc:subject","label":"Dc Subject","values":["F100 - Chemistry"]}]},{"id":"language_rights","label":"Language and Rights","entries":[{"key":"dc:language","label":"Dc Language","values":["en"]}]},{"id":"identifiers","label":"Identifiers","entries":[{"key":"dc:identifier.uri","label":"Identifier URI","values":["https://knowledge.lancashire.ac.uk/id/eprint/20338/1/20338%20MD.%20Moshfiqur%20Rahman%20Nov95%20some%20chemistry%20of%20bromobenzopyrans%20degree%20of%20Doctor%20of%20Philosophy%20unpublished%20Nov95%20University%20of%20Central%20Lancashire%20Chemistry%20294.pdf"]}]},{"id":"additional","label":"Additional Metadata","entries":[{"key":"dc:description.abstract","label":"Abstract","values":["A series of 2,2-disubstituted chroman-4-ones has been prepared by the base catalysed condensation of a carbonyl compound with 2'-hydroxyacetophenone. Chroman-4-ones substituted in the aromatic ring were more conveniently prepared by the cyclocondensation of a phenol with an a,j3-unsaturated carboxylic acid. 2,4-Dimethylphenyl-3-methylbut-2-enoate was obtained as a by-product during the preparation of 2,2,6,8 tetramethylchroman-4-one from 2,4-dimethyiphenol and 3,3-dimethylacrylic acid in polyphosphoric acid. The ester in polyphosphoric acid underwent a Fries rearrangement to give the chroman-4-one, but in methanesulfonic acid it gave 3,4-dihydro-4,4,6,8-tetramethylcoumarin. Reduction and dehydration of the resulting chroman-4-ols gave the 2H-chromenes in excellent yield. Addition of N-bromosuccinimide in moist dimethyl sulfoxide to the 2H-chromenes gave the trans-3-bromochroman-4-ols in good yield. Subsequent dehydration using a catalytic amount of 4-toluenesulfonic acid in refluxing toluene afforded the 3-bromo-2H-chromenes. A novel bis-4-(3-bromochromanyl)ether was isolated from the dehydration of 3-bromo-2,2-dimethylchroman-4-ol. Its formation is thought to arise from intermolecular capture of the benzylic cation by a second molecule of the bromohydrin. 4-Bromo-2H-chromenes have been obtained in a single step and in excellent yield from the chroman-4-ones by reaction with phosphorus tribromide. A novel 2H-chromene-4-phosphonic acid was characterised from the reaction of 2,2-dimethylchroman-4-one with PBr3. Lithiation of the 4-bromo-2H-chromenes gave the 4-chromenyl lithium which reacted with a range of electrophiles to afford novel 4-substituted 2H-chromenes. However, lithiation of the isomeric 3-bromo-2H-chromenes did not lead to the corresponding 3-substituted 2H-chromenes but gave instead substituted 2'-hydroxyphenyl allenes in good yields. This method constitutes a new route to the allene system. Reactivity of the allenes towards bromination, hydroboration and cycloaddition reactions have been investigated. 3,4-Dibromo-2,2,6,8-tetramethyl-2H-chromene has been prepared by the bromination of 4.bromo-2,2,6,8-tetramethyl-2H-chromene. 3,4,7-Tribromo-2,2,6,8-tetramethyl- 2H-chromene was obtained as a by-product The reaction of 3,4-dibromo-2,2,6,8-tetramethyl-2H-chromene with alkyllithium reagents gave mainly the 4-ailcyl substituted 211-chromenes with trace amounts of the 4-unsubstituted 2H-chromenes. Reaction of 3,4-dibromo-2,2,6,8-tetramethyl-2H-chrOmene with magnesium in THF in the presence of furans gave the Diels-Alder adducts, as a result of the trapping of the heteroaryne, 3,4-didehydro-2H[ 1 ]ben zopyran. This reaction constitutes the generation of a novel aryne. Diels-Alder adducts obtained by the use of 2,5-dimethylfuran and 1,3-diphenylisobenzofuran have been aromatised providing facile access to dibenzo[bdjpyrans."]},{"key":"dc:format","label":"Dc Format","values":["application/pdf"]},{"key":"dc:title","label":"Title","values":["Some chemistry of bromobenzopyrans"]}]}],"canonical_facts":{"dc:creator":["Rahman, Md. Moshfiqur"],"dc:date":["1995-11-01"],"dc:date.issued":["1995-11"],"dc:description.abstract":["A series of 2,2-disubstituted chroman-4-ones has been prepared by the base catalysed condensation of a carbonyl compound with 2'-hydroxyacetophenone. Chroman-4-ones substituted in the aromatic ring were more conveniently prepared by the cyclocondensation of a phenol with an a,j3-unsaturated carboxylic acid. 2,4-Dimethylphenyl-3-methylbut-2-enoate was obtained as a by-product during the preparation of 2,2,6,8 tetramethylchroman-4-one from 2,4-dimethyiphenol and 3,3-dimethylacrylic acid in polyphosphoric acid. The ester in polyphosphoric acid underwent a Fries rearrangement to give the chroman-4-one, but in methanesulfonic acid it gave 3,4-dihydro-4,4,6,8-tetramethylcoumarin. Reduction and dehydration of the resulting chroman-4-ols gave the 2H-chromenes in excellent yield. Addition of N-bromosuccinimide in moist dimethyl sulfoxide to the 2H-chromenes gave the trans-3-bromochroman-4-ols in good yield. Subsequent dehydration using a catalytic amount of 4-toluenesulfonic acid in refluxing toluene afforded the 3-bromo-2H-chromenes. A novel bis-4-(3-bromochromanyl)ether was isolated from the dehydration of 3-bromo-2,2-dimethylchroman-4-ol. Its formation is thought to arise from intermolecular capture of the benzylic cation by a second molecule of the bromohydrin. 4-Bromo-2H-chromenes have been obtained in a single step and in excellent yield from the chroman-4-ones by reaction with phosphorus tribromide. A novel 2H-chromene-4-phosphonic acid was characterised from the reaction of 2,2-dimethylchroman-4-one with PBr3. Lithiation of the 4-bromo-2H-chromenes gave the 4-chromenyl lithium which reacted with a range of electrophiles to afford novel 4-substituted 2H-chromenes. However, lithiation of the isomeric 3-bromo-2H-chromenes did not lead to the corresponding 3-substituted 2H-chromenes but gave instead substituted 2'-hydroxyphenyl allenes in good yields. This method constitutes a new route to the allene system. Reactivity of the allenes towards bromination, hydroboration and cycloaddition reactions have been investigated. 3,4-Dibromo-2,2,6,8-tetramethyl-2H-chromene has been prepared by the bromination of 4.bromo-2,2,6,8-tetramethyl-2H-chromene. 3,4,7-Tribromo-2,2,6,8-tetramethyl- 2H-chromene was obtained as a by-product The reaction of 3,4-dibromo-2,2,6,8-tetramethyl-2H-chromene with alkyllithium reagents gave mainly the 4-ailcyl substituted 211-chromenes with trace amounts of the 4-unsubstituted 2H-chromenes. Reaction of 3,4-dibromo-2,2,6,8-tetramethyl-2H-chrOmene with magnesium in THF in the presence of furans gave the Diels-Alder adducts, as a result of the trapping of the heteroaryne, 3,4-didehydro-2H[ 1 ]ben zopyran. This reaction constitutes the generation of a novel aryne. Diels-Alder adducts obtained by the use of 2,5-dimethylfuran and 1,3-diphenylisobenzofuran have been aromatised providing facile access to dibenzo[bdjpyrans."],"dc:format":["application/pdf"],"dc:identifier.uri":["https://knowledge.lancashire.ac.uk/id/eprint/20338/1/20338%20MD.%20Moshfiqur%20Rahman%20Nov95%20some%20chemistry%20of%20bromobenzopyrans%20degree%20of%20Doctor%20of%20Philosophy%20unpublished%20Nov95%20University%20of%20Central%20Lancashire%20Chemistry%20294.pdf"],"dc:language":["en"],"dc:publisher.department":["Chemistry"],"dc:publisher.institution":["University of Central Lancashire"],"dc:relation.isreferencedby":["https://knowledge.lancashire.ac.uk/id/eprint/20338/"],"dc:subject":["F100 - Chemistry"],"dc:title":["Some chemistry of bromobenzopyrans"],"dc:type":["Thesis"],"dc:type.qualificationlevel":["doctoral"],"dc:type.qualificationname":["phd"]},"updated_at":"2026-07-24T01:36:10Z"}