Syntheses and Reactions of Crown Ether‐Bridged Stilbenes

Merz, Andreas; Karl, A.; Futterer, Thomas; Stacherdinger, Natascha; Schneider, Oliver; Lex, Johann; Luboch, Elżbieta; Biernat, Jan F.

doi:10.1002/jlac.199419941211

Cited by 40 publications

(11 citation statements)

References 43 publications

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“…17 Compound 1 was obtained from Fluka, the diastereomeric mixture of 2 was prepared according to Ref. 12, 6-(methanesulfonyloxy)hexene was prepared by a general procedure 18 and used without purification.…”

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A Short and Efficient Synthesis of 3,4-Dialkoxypyrroles

Merz¹,

Meyer²

1999

Synthesis

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3,4-Dialkoxypyrroles are obtained in four steps from commercially available 2,5-dimethoxy-2,5-dihydrofuran (1) . The dihydrofuran 1 is first oxidized by KMnO 4 to the diol 2 which is bisalkylated to 3aÐd. Reaction of the in situ generated dialdehydes with a primary amine affords the N -substituted dialkoxypyrroles 4aÐm . N -Benzyl-3,4-dialkoxypyrroles and N -allyl-dialkoxypyrroles are cleaved by sodium in liquid ammonia affording N -unsubstituted dialkoxypyrroles 5aÐc in good overall yield.The most simple synthesis of porphyrins is the condensation of symmetric 2,5-unsubstituted pyrroles with an aldehyde and subsequent or concommitant dehydrogenation, 1 however, the preparation of suitable precursors, e.g. 3,4-diethylpyrrole, require several steps and only few established protocols exist. 2 Another series of suitable symmetric pyrrole precursors are 3,4-dialkoxypyrroles, the synthesis of which has only recently been accomplished. 3,4 A variety of octaalkoxyporphyrins 4,5 have been obtained, including tetra-crowned porphyrins 6 and also liquid crystalline species with decyloxy side chains. 7 Furthermore, dialkoxypyrroles are electrochemically oxidized to highly conducting polypyrroles linked uniformly in 2,5 position. 8 Although substantial quantities of 3,4-dimethoxypyrrole (5a) can be prepared in six straightforward steps with 22% total yield, this is not generally true for higher homologs. 4 In this paper we describe a significantly shorter synthesis of N-substituted 3,4-dialkoxypyrroles 4aÐm in three steps, and N-unsubstituted pyrroles 5 in one additional step (Scheme). Commercial 2,5-dimethoxy-2,5-dihydrofuran (1) 9 is a mixture of the achiral cis and racemic trans forms with various compositions depending on the source, e.g. 70:30, 10 or 54:46 in this work. The oxidation of 1 with KMnO 4 yields 2 11 in much the same diastereomeric ratio of the achiral ttc and chiral cct isomers, although under certain conditions 10 cis -1 is reported to react faster. In our hands, higher boiling fractions of 2 from simple vacuum distillation consist of almost pure ttc -2 . A third isomer with all cis arrangement of all four substituents obviously has been never observed. 10 Depending on the nature of the alkylating agent different procedures have been developed for the alkyation step. Due to the generally high yields in these procedures to give the diastereomeric mix-

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A Short and Efficient Synthesis of 3,4-Dialkoxypyrroles

Merz¹,

Meyer²

1999

Synthesis

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“…Thus, the observed chemical shift for the intra‐annular protons of 3a strongly suggests that the molecule adopts a syn ‐conformation. Previous work has shown the chemical shifts of olefinic protons for ( E )‐ and (Z) ‐olefins to be at δ < 7.4 ppm and δ < 6.9 ppm repectively . In the case of 3a , the olefinic bridge protons were observed as a singlet at δ = 6.79 ppm indicating that the structure of 3a is a ( Z )‐ syn ‐isomer.…”

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confidence: 89%

Synthesis and Structures of [2.n]Metacyclophan‐1‐enes and their Conversion to Highly Strained [2.n]Metacyclophane‐1‐ynes

et al. 2020

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The syntheses of syn‐[2.n]metacyclophan‐1‐enes (n = 5, 6, 8) in good yields using the McMurry cyclization of 1,n‐bis(3‐formyl‐4‐methoxyphenyl)alkanes are reported. Conversion of syn‐[2.6]‐ and [2.8]metacyclophan‐1‐enes to the corresponding highly strained syn‐type [2.6]‐ and [2.8]metacyclophane‐1‐ynes was achieved by successive bromination and dehydrobromination reactions. An attempted trapping reaction of the putative corresponding [2.5]metacyclophane‐1‐yne by Diels–Alder reaction with 1,3‐diphenylisobenzofuran failed due to its smaller ring size and strained structure. X‐ray crystallographic analyses show that the triple bonds in syn‐[2.6]‐ and [2.8]metacyclophane‐1‐ynes are distorted from linearity with bond angles of 156.7° and 161.4°, respectively. A DFT (Density Functional Theory) computational study was conducted to determine the stabilities of different conformations of the target compounds.

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“…The structure of ( E )‐ 4 was determined by elemental analysis and spectroscopic data. In 1 H NMR spectroscopy, a singlet from the olefinic protons of the E isomer should be observed at a lower field ( δ > 7.4 ppm) than those of the Z olefinic protons ( δ < 6.9 ppm) 17. As expected, the 1 H NMR spectrum (300 MHz, CDCl 3 ) of 4 shows a pair of doublets ( J = 15.9 Hz) at δ = 7.33 and 7.92 ppm for the E ‐olefinic protons and a singlet at δ = 3.88 ppm for the methoxy protons.…”

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Synthesis, Structural, and Photophysical Properties of the First Member of the Class of Pyrene‐Based [4]Helicenes

Feng

Paudel

et al. 2013

Eur J Org Chem

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A convenient route to a new class of pyrene‐based [4]helicenes is presented. Wittig reaction of 7‐tert‐butyl‐1,3‐dimethyl‐5‐formylpyrene with benzyltriphenylphosphonium salts in the presence of nBuLi afforded 7‐tert‐butyl‐1,3‐dimethyl‐5‐(phenylethenyl)pyrenes, from which 4,5‐naphthalene annulated aromatic [4]helicenes, namely 7‐tert‐butyl‐1,3‐dimethyl‐13‐methoxydibenzo[ij,no]tetraphene and 7‐tert‐butyl‐1,3,12,14‐tetramethyldibenzo[ij,no]tetraphene, were obtained by photoinduced intramolecular cyclization. The chemical structures of these [4]helicenes were determined on the basis of their elemental analyses and spectroscopic data. The helicity in the synthesized [4]helicene induced by the presence of the second methyl group in the fjord region is discussed in detail. The photophysical and electrochemical properties of these newly developed [4]helicenes were fully investigated by UV/Vis absorption and photoluminescence spectrphotometry, and cyclic voltammetry (CV), and the crystal structures were determined for two examples.

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Syntheses and Reactions of Crown Ether‐Bridged Stilbenes

Cited by 40 publications

References 43 publications

A Short and Efficient Synthesis of 3,4-Dialkoxypyrroles

A Short and Efficient Synthesis of 3,4-Dialkoxypyrroles

Synthesis and Structures of [2.n]Metacyclophan‐1‐enes and their Conversion to Highly Strained [2.n]Metacyclophane‐1‐ynes

Synthesis, Structural, and Photophysical Properties of the First Member of the Class of Pyrene‐Based [4]Helicenes

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