Concise synthesis of α-substituted 2-benzofuranmethamines and other 2-subsituted benzofurans via α-substituted 2-benzofuranmethyl carbocation intermediates
Propargyl amines 4, where R3 is aryl, undergo 5-exo-dig cyclization reactions under relatively mild conditions (AgNO3, DMF, 60 C, 1 h) to give 3-amino-2,3-dihydro-2-arylmethylidenebenzofurans 5 (R 3 = aryl). In contrast, substrates where R3 is alkyl undergo competing 6-endo-dig and 5-exo-dig cycliza...
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th-cmuir.6653943832-524062018-09-04T09:24:52Z Concise synthesis of α-substituted 2-benzofuranmethamines and other 2-subsituted benzofurans via α-substituted 2-benzofuranmethyl carbocation intermediates Nikhom Wongsa Ubonta Sommart Thunwadee Ritthiwigrom Arife Yazici Somdej Kanokmedhakul Kwanjai Kanokmedhakul Anthony C. Willis Stephen G. Pyne Chemistry Propargyl amines 4, where R3 is aryl, undergo 5-exo-dig cyclization reactions under relatively mild conditions (AgNO3, DMF, 60 C, 1 h) to give 3-amino-2,3-dihydro-2-arylmethylidenebenzofurans 5 (R 3 = aryl). In contrast, substrates where R3 is alkyl undergo competing 6-endo-dig and 5-exo-dig cyclization processes. The hydroxymethyl substrate 4 (R3 = CH2OH), however, was smoothly converted to its corresponding 5-exo-dig cyclization product 5, likely due to the assistance of the primary hydroxyl group in the 5-exo-dig cyclization process by silver cation coordination. Under more enforcing conditions (AgNO3, DMF, 100 C, 18 h), the initially formed products 5 undergo a 1,3-allylic rearrangement to their corresponding 2-substituted benzofuran derivatives 6. This rearrangement can also be effected by treating 5 with AgNO3 in DMF at 100 C for 18 h or BF3·Et 2O at rt. 2-(3-Butenyl)benzofurans 7 (Nu = allyl) can be prepared by treatment of 5 with BF3·Et2O and allyltributylstannane. Furan and MeOH could also be employed as external nucleophiles in these BF3·Et2O-promoted reactions. © 2013 American Chemical Society. 2018-09-04T09:24:52Z 2018-09-04T09:24:52Z 2013-02-01 Journal 15206904 00223263 2-s2.0-84873325933 10.1021/jo302554v https://www.scopus.com/inward/record.uri?partnerID=HzOxMe3b&scp=84873325933&origin=inward http://cmuir.cmu.ac.th/jspui/handle/6653943832/52406 |
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Chemistry Nikhom Wongsa Ubonta Sommart Thunwadee Ritthiwigrom Arife Yazici Somdej Kanokmedhakul Kwanjai Kanokmedhakul Anthony C. Willis Stephen G. Pyne Concise synthesis of α-substituted 2-benzofuranmethamines and other 2-subsituted benzofurans via α-substituted 2-benzofuranmethyl carbocation intermediates |
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Propargyl amines 4, where R3 is aryl, undergo 5-exo-dig cyclization reactions under relatively mild conditions (AgNO3, DMF, 60 C, 1 h) to give 3-amino-2,3-dihydro-2-arylmethylidenebenzofurans 5 (R 3 = aryl). In contrast, substrates where R3 is alkyl undergo competing 6-endo-dig and 5-exo-dig cyclization processes. The hydroxymethyl substrate 4 (R3 = CH2OH), however, was smoothly converted to its corresponding 5-exo-dig cyclization product 5, likely due to the assistance of the primary hydroxyl group in the 5-exo-dig cyclization process by silver cation coordination. Under more enforcing conditions (AgNO3, DMF, 100 C, 18 h), the initially formed products 5 undergo a 1,3-allylic rearrangement to their corresponding 2-substituted benzofuran derivatives 6. This rearrangement can also be effected by treating 5 with AgNO3 in DMF at 100 C for 18 h or BF3·Et 2O at rt. 2-(3-Butenyl)benzofurans 7 (Nu = allyl) can be prepared by treatment of 5 with BF3·Et2O and allyltributylstannane. Furan and MeOH could also be employed as external nucleophiles in these BF3·Et2O-promoted reactions. © 2013 American Chemical Society. |
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Nikhom Wongsa Ubonta Sommart Thunwadee Ritthiwigrom Arife Yazici Somdej Kanokmedhakul Kwanjai Kanokmedhakul Anthony C. Willis Stephen G. Pyne |
author_facet |
Nikhom Wongsa Ubonta Sommart Thunwadee Ritthiwigrom Arife Yazici Somdej Kanokmedhakul Kwanjai Kanokmedhakul Anthony C. Willis Stephen G. Pyne |
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Nikhom Wongsa |
title |
Concise synthesis of α-substituted 2-benzofuranmethamines and other 2-subsituted benzofurans via α-substituted 2-benzofuranmethyl carbocation intermediates |
title_short |
Concise synthesis of α-substituted 2-benzofuranmethamines and other 2-subsituted benzofurans via α-substituted 2-benzofuranmethyl carbocation intermediates |
title_full |
Concise synthesis of α-substituted 2-benzofuranmethamines and other 2-subsituted benzofurans via α-substituted 2-benzofuranmethyl carbocation intermediates |
title_fullStr |
Concise synthesis of α-substituted 2-benzofuranmethamines and other 2-subsituted benzofurans via α-substituted 2-benzofuranmethyl carbocation intermediates |
title_full_unstemmed |
Concise synthesis of α-substituted 2-benzofuranmethamines and other 2-subsituted benzofurans via α-substituted 2-benzofuranmethyl carbocation intermediates |
title_sort |
concise synthesis of α-substituted 2-benzofuranmethamines and other 2-subsituted benzofurans via α-substituted 2-benzofuranmethyl carbocation intermediates |
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2018 |
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https://www.scopus.com/inward/record.uri?partnerID=HzOxMe3b&scp=84873325933&origin=inward http://cmuir.cmu.ac.th/jspui/handle/6653943832/52406 |
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