The University of Manchester Research Tetra- and Octapyrroles Synthesized from Confusion and Fusion Approaches DOI: 10.1021/acs.orglett.6b02495 Document Version Accepted author manuscript Link to publication record in Manchester Research Explorer Citation for published version (APA): Kong, J., Zhang, Q., Savage, M., Li, M., Li, X., Yang, S., Liang, X., Zhu, W., Ågren, H., & Xie, Y. (2016). Tetra- and Octapyrroles Synthesized from Confusion and Fusion Approaches. Organic Letters, 18. https://doi.org/10.1021/acs.orglett.6b02495 Published in: Organic Letters Citing this paper Please note that where the full-text provided on Manchester Research Explorer is the Author Accepted Manuscript or Proof version this may differ from the final Published version. If citing, it is advised that you check and use the publisher's definitive version. 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Tetra - and Octapyrroles Synthesized from Confusion and Fusion Approaches Journal: Organic Letters Manuscript ID ol-2016-02495b.R1 Manuscript Type: Communication Date Submitted by the Author: 15-Sep-2016 Complete List of Authors: Kong, Jiahui; East China University of Science and Technology, School of Chemistry and Molecular Engineering zhang, qiong; ShanghaiTech University, School of Physical Science and Technology Savage, Mathew; University of Manchester, Li, Minzhi; School of Chemistry and Chemcal Engineering, Li, Xin; East China University of Science & Technology Yang, Sihai; University of Manchester, School of Chemistry Liang, Xu; Jiangsu University, School of Chemistry and Chemical Engineering Ågren, Hans; Royal Institute of Technology, Laboratory of Theoretical Chemistry Zhu, Weihua; University of Houston, Department of Chemistry; Jiangsu University, School of Chemistry and Chemical Engineering Xie, Yongshu; East China University of Science and Technology, School of Chemistry ACS Paragon Plus Environment Page 1 of 4 Submitted to Organic Letters 1 2 3 4 Tetra- and Octapyrroles 5 6 Synthesized from Confusion and 7 8 Fusion Approaches 9 10 Jiahui Kong, † Qiong Zhang, ‡ Mathew Savage, ξ Minzhi Li,§ Xin Li, ς Sihai 11 ξ § § ς ,† 12 Yang , Xu Liang, Weihua Zhu, Hans Ågren, and Yongshu Xie* 13 † 14 Key Laboratory for Advanced Materials and Institute of Fine Chemicals, 15 School of Chemistry and Molecular Engineering, East China University of Science and Technology, Shanghai 200237, China 16 ‡ 17 School of Physical Science and Technology, ShanghaiTech University, Shanghai 200031, China 18 ξ 19 School of Chemistry, University of Manchester, Manchester, m13 9pl, UK § 20 School of Chemistry & Chemical Engineering, Jiangsu University, Zhenjiang 21 212013, China ς 22 Department of Theoretical Chemistry and Biology, School of Biotechnology, 23 KTH Royal Institute of Technology, Stockholm, Se-10691, Sweden 24 [email protected] 25 26 Received Date (will be automatically inserted after manuscript is accepted) 27 28 29 30 ABSTRACT 31 32 33 34 35 36 37 38 By oxidation of an alternately N-confused bilane in CH 2Cl 2, a C-N fused tetrapyrrin (1) was synthesized, which bears a 5.5.5-tricyclic ring generated from intramolecular C-N linkage. When CH CN was used as the reaction medium, a 39 3 multiply C-N fused octapyrrolic dimer (2) was also obtained, which contained two 5.5.5.7.5-pentacyclic moieties and a 40 bipyrrole unit generated from intramolecular C-N linkage and intermolecular C-C linkage, respectively. 1 could 41 coordinate with Ni(acac) 2 to afford a mixed-ligand complex (Ni-1-acac). 42 43 44 45 As a class of promising intermediates in synthetic with one of the terminal α positions blocked with an acyl 46 porphyrin chemistry,1 and coordinating ligands for substituent (Scheme.1).7 To further enrich the structural 47 constructing supramolecular assemblies 2 and sensing diversity, N-confused pyrrole units, i.e., α,β’-linked 48 various ions,3 linear oligopyrroles with pyrrole units pyrroles, may be employed. 8 Thus, a number of bilane 49 interconnected at the α positions have attracted extensive isomers have been reported (Scheme 1, a-e).9-10 Owing to 50 attentions in recent years.4 Tetrapyrrolic bilanes are the higher reactivity of N-confused pyrrole units, 51 unique members of linear oligopyrroles, because they oxidation of these confused bilanes gives rise to a 52 contain the same numbers of pyrrolic units as porphyrins, diversity of porphyrin analogues. For example, the singly 53 and they have been used for the syntheses of porphyrins N-confused bilanes a and b could be oxidized to afford 54 and their analogues, such as corroles, through confused corrole isomers.9 If two confused pyrrole units 55 acid-catalyzed condensation or oxidative cyclization.5,6 In are introduced, three doubly N-confused bilanes 56 these cases, terminal pyrrole units are interconnected at (Scheme.1, c-e) may be developed. The doubly terminal 57 the free α positions. Supplementary to the macrocyclic confused bilane c and the doubly adjacent confused bilane 58 compounds, we have reported an example of synthesizing d could be oxidatively cyclized to afford corrorin and 59 a linear octapyrrole by oxidative dimerization of a bilane C-fused norrole, respectively. 8d ,10 60 ACS Paragon Plus Environment Submitted to Organic Letters Page 2 of 4 fields. The characters observed for 1 in the NMR and 1 Scheme 1 . Examples of bilanes, confused bilanes and the HRMS were consistent with the intramolecular C-N fused 2 structure (vide infra ), generated from intramolecular corresponding oxidation products (Ar=C 6F5). 3 Ar Ar Ar O oxidative coupling between the NH and α CH moieties. It 4 Ar N Ar N Ar is noteworthy that 1 still contains free α positions. NH HN H H NH HN N 5 Ar Ar Ar Ar N N Especially, the confused pyrrole ring still contains two NH HN N 6 NH HN H H α O N Ar N free positions, which may undergo further fusion or 7 Ar Ar Ar O Ar expansion reactions. Thus, we attempted the further 8 terminally bilane blocked bilane octapyrrole oxidation of 1 with various oxidants. Unfortunately, only 9 Ar Ar Ar Ar H some unidentified decomposed compounds were detected N 10 NH from the reactions. NH HN NH NH HN NH 11 Ar Ar Ar Ar Ar Ar Ar Ar 12 NH NH HN NH N N N N 13 H H H H a b c d Scheme 2. Syntheses of 1 and 2 by oxidation of bilane e with 14 Ar Ar Ar Ar H DDQ in CH Cl and CH CN, respectively, and coordination of 1 15 N 2 2 3 N HN NH NH N HN NH with Ni(II). 16 Ar Ar Ar Ar Ar Ar Ar NH Ar N HN N 17 N N NH HN 18 H 19 corrole isomers corrorin C-fused norrole 20 Ar Ar Ar Ar 21 N HN Ar H N 22 HN N N N Ar Ar N Ar N N Ar N 23 NH NH H Ar N Ar 24 N NH Ar H e 25 1 2 26 27 28 In spite of the excellent examples of porphyrin analogues 29 obtained from the singly and doubly confused bilanes, the 30 oxidation of the alternately N-confused bilane (e) remains 31 unexplored. 11 In this work, simply by oxidizing e, a C-N 32 fused tetrapyrrin (1) and a multiply C-N fused 33 octapyrrolic dimer (2) were obtained, and both an 34 intramolecular C-N linkage and intermolecular C-C 35 linkages were observed. Surprisingly, no porphyrin 36 analogue was obtained at all. To check the possibility of 37 metal coordination, a Ni(II) complex of 1 was also Considering that 1 is already fully conjugated and the 38 synthesized. Despite the abundant examples of reactivity may have been decreased, we returned to check 39 intramolecular ring fusion in porphyrin analogues,12 the oxidation conditions for the precursor e. Interestingly, 40 ring-fused linear oligopyrroles are still quite rare. This when e was oxidized with 3.0 equiv DDQ in CH 3CN 41 work demonstrates the possibility of combined confusion (Scheme 2, Route B), 2 was generated in addition to 1. 42 and fusion approaches for synthesizing novel linear Although 2 was not fully conjugated ( vide infra ), the 43 oligopyrroles applicable in coordination chemistry and further oxidation of 2 with DDQ only afforded some 44 synthetic porphyrinoid chemistry. decomposed compounds. Whereas, 2 was not observed 45 The reaction details are outlined in Scheme 2. Bilane when the reaction was performed in CH 2Cl 2, toluene or + 46 e was first oxidized with 3.0 equiv 2,3-dichloro- THF. The HRMS (2+Na ) of compound 2 (Figure S6) 47 5,6-dicyano-1,4-benzo-quinone (DDQ) in CH 2Cl 2 (Route shows a molecular peak at m/z of 1611.1068, roughly 48 A), affording 1 in a 45% yield. When FeCl 3 or MnO 2 was double of that for e, implying that 2 might be a dimerized 1 49 used as the oxidant, no identifiable compound could be form of e.