Synthetic methods of pyrrolidines from N-hydroxylsulfonamides by using bis[copper(I) trifluoromethanesulfonate]-benzene complex as a redox catalyst

The synthesis of azaheterocycles which are an important class of natural products and pharmacologically active compounds has been investigated for a long time and many methodologies were reported. Radical reactions were also applied to the synthesis of azaheterocycles but not very widely. In this th...

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Main Author: Liu, Zhenhong
Other Authors: Koichi Narasaka
Format: Theses and Dissertations
Language:English
Published: 2013
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Online Access:https://hdl.handle.net/10356/51063
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Institution: Nanyang Technological University
Language: English
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spelling sg-ntu-dr.10356-510632023-03-01T00:01:56Z Synthetic methods of pyrrolidines from N-hydroxylsulfonamides by using bis[copper(I) trifluoromethanesulfonate]-benzene complex as a redox catalyst Liu, Zhenhong Koichi Narasaka School of Physical and Mathematical Sciences DRNTU::Science::Chemistry::Organic chemistry::Organic synthesis The synthesis of azaheterocycles which are an important class of natural products and pharmacologically active compounds has been investigated for a long time and many methodologies were reported. Radical reactions were also applied to the synthesis of azaheterocycles but not very widely. In this thesis, the author describes the development of catalytic methods to synthesize 2,5-disubstituted pyrrolidines from N-alkenyl, alkynyl and alkyl N-benzoyloxysulfonamides by using (CuOTf)2•C6H6 as a redox catalyst. These reactions involve sulfonamidyl radicals as the key intermediates, which are generated by one electron reduction of N-benzoyloxysulfonamides. Thus generated sulfonamidyl radicals successively follow the two kinds of steps; 1) addition to intramolecular unsaturated bond or 2) 1,5- hydrogen abstraction. Firstly, addition of sulfonamidyl radicals to intramolecular unsaturated bond was studied, and after the screening of redox catalysts, (CuOTf)2•C6H6 was found to act as an efficient catalyst as shown in eq 1 and 2. From N-4-alkenyl-N-benzoyloxysulfonamides 1, 2,5-disubstuted pyrrolidines 2 were obtained (equation 1), and acetylenic sulfonamides 3 were also converted to pyrrolidines 4 under the same reaction conditions (equation 2). It was expected that 6-membered products could be formed by the cyclization of N-5-alkenyl- or 5-alkynyl-N-benzoyloxysulfonamides 5 which has one more tether than the above substrate 1. However, instead of 6-membered piperidines, 5-membered pyrrolidines 6 were obtained as the major products. Abstraction of allylic or propargylic hydrogens by sulfonamidyl radicals was more favorable than the addition to the double or triple bonds (equation 3). Moreover, functionalization of unreactive C-H bonds of N-alkylsulfonamides 7 was achieved via 1,5-hydrogen abstraction to provide pyrrolidine derivatives. For example, spiro compound 8 was prepared in a good yield (equation 4). Thus, (CuOTf)2•C6H6-catalyzed cyclization of N-alkenyl, alkynyl and alkyl N- benzoyloxysulfonamides afforded efficient methods to prepare pyrrolidine derivatives via the sulfonamidyl radical formation. Remote functionalizations of unreactive C-H were also achieved in a catalytic manner. DOCTOR OF PHILOSOPHY (SPMS) 2013-01-03T04:34:30Z 2013-01-03T04:34:30Z 2012 2012 Thesis Liu, Z. (2012). Synthetic methods of pyrrolidines from N-hydroxylsulfonamides by using bis[copper(I) trifluoromethanesulfonate]-benzene complex as a redox catalyst. Doctoral thesis, Nanyang Technological University, Singapore. https://hdl.handle.net/10356/51063 10.32657/10356/51063 en 178 p. application/pdf
institution Nanyang Technological University
building NTU Library
continent Asia
country Singapore
Singapore
content_provider NTU Library
collection DR-NTU
language English
topic DRNTU::Science::Chemistry::Organic chemistry::Organic synthesis
spellingShingle DRNTU::Science::Chemistry::Organic chemistry::Organic synthesis
Liu, Zhenhong
Synthetic methods of pyrrolidines from N-hydroxylsulfonamides by using bis[copper(I) trifluoromethanesulfonate]-benzene complex as a redox catalyst
description The synthesis of azaheterocycles which are an important class of natural products and pharmacologically active compounds has been investigated for a long time and many methodologies were reported. Radical reactions were also applied to the synthesis of azaheterocycles but not very widely. In this thesis, the author describes the development of catalytic methods to synthesize 2,5-disubstituted pyrrolidines from N-alkenyl, alkynyl and alkyl N-benzoyloxysulfonamides by using (CuOTf)2•C6H6 as a redox catalyst. These reactions involve sulfonamidyl radicals as the key intermediates, which are generated by one electron reduction of N-benzoyloxysulfonamides. Thus generated sulfonamidyl radicals successively follow the two kinds of steps; 1) addition to intramolecular unsaturated bond or 2) 1,5- hydrogen abstraction. Firstly, addition of sulfonamidyl radicals to intramolecular unsaturated bond was studied, and after the screening of redox catalysts, (CuOTf)2•C6H6 was found to act as an efficient catalyst as shown in eq 1 and 2. From N-4-alkenyl-N-benzoyloxysulfonamides 1, 2,5-disubstuted pyrrolidines 2 were obtained (equation 1), and acetylenic sulfonamides 3 were also converted to pyrrolidines 4 under the same reaction conditions (equation 2). It was expected that 6-membered products could be formed by the cyclization of N-5-alkenyl- or 5-alkynyl-N-benzoyloxysulfonamides 5 which has one more tether than the above substrate 1. However, instead of 6-membered piperidines, 5-membered pyrrolidines 6 were obtained as the major products. Abstraction of allylic or propargylic hydrogens by sulfonamidyl radicals was more favorable than the addition to the double or triple bonds (equation 3). Moreover, functionalization of unreactive C-H bonds of N-alkylsulfonamides 7 was achieved via 1,5-hydrogen abstraction to provide pyrrolidine derivatives. For example, spiro compound 8 was prepared in a good yield (equation 4). Thus, (CuOTf)2•C6H6-catalyzed cyclization of N-alkenyl, alkynyl and alkyl N- benzoyloxysulfonamides afforded efficient methods to prepare pyrrolidine derivatives via the sulfonamidyl radical formation. Remote functionalizations of unreactive C-H were also achieved in a catalytic manner.
author2 Koichi Narasaka
author_facet Koichi Narasaka
Liu, Zhenhong
format Theses and Dissertations
author Liu, Zhenhong
author_sort Liu, Zhenhong
title Synthetic methods of pyrrolidines from N-hydroxylsulfonamides by using bis[copper(I) trifluoromethanesulfonate]-benzene complex as a redox catalyst
title_short Synthetic methods of pyrrolidines from N-hydroxylsulfonamides by using bis[copper(I) trifluoromethanesulfonate]-benzene complex as a redox catalyst
title_full Synthetic methods of pyrrolidines from N-hydroxylsulfonamides by using bis[copper(I) trifluoromethanesulfonate]-benzene complex as a redox catalyst
title_fullStr Synthetic methods of pyrrolidines from N-hydroxylsulfonamides by using bis[copper(I) trifluoromethanesulfonate]-benzene complex as a redox catalyst
title_full_unstemmed Synthetic methods of pyrrolidines from N-hydroxylsulfonamides by using bis[copper(I) trifluoromethanesulfonate]-benzene complex as a redox catalyst
title_sort synthetic methods of pyrrolidines from n-hydroxylsulfonamides by using bis[copper(i) trifluoromethanesulfonate]-benzene complex as a redox catalyst
publishDate 2013
url https://hdl.handle.net/10356/51063
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