Enantioselective Synthesis and Circular Dichroism of Endocyclic Allenes

Zelder, Claudia; Krause, Norbert

doi:10.1002/ejoc.200400408

Cited by 25 publications

(7 citation statements)

References 16 publications

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“…An efficient route to connect the TTF moiety into the allenic framework was established by a palladium-catalyzed cross-coupling reaction as shown in Scheme 1 [23,24]. Starting with ketone 4 , prepared by Friedel-Crafts acylation of pyrene, the reaction with the lithiated acetylide of phenylacetylene in THF at low temperature afforded propargyl alcohol 5 quantitatively.…”

Section: Resultsmentioning

confidence: 99%

Chiroptical Properties and the Racemization of Pyrene and Tetrathiafulvalene-Substituted Allene: Substitution and Solvent Effects on Racemization in Tetrathiafulvalenylallene

et al. 2014

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Dissymmetric 1,3-diphenylallene derivative 3 connected with 4,5-bis(methylthio)tetrathiafulvalenyl and 1-pyrenyl substituents was prepared and characterized. The molecular structure was determined by X-ray crystallographic analysis. Optical resolution was accomplished using a recycling chiral HPLC, and its chiroptical properties were examined with optical rotation and electronic circular dichroism (ECD) spectra. The title compound underwent photoracemization under daylight. This behavior was investigated in various solvents and compared with that of 1,3-bis(tetrathiafulvalenyl)allene (bis-TTFallene) derivative 2. The first-order rate plot of the intensity of the ECD spectra at a given time interval gave the rate of racemization. Mild racemization was observed in polar solvents, whereas a relatively fast rate was obtained in less polar solvents. In addition, the TTF groups of the allene also accelerate the racemization rate. These results suggest that the racemization mechanism occurs via a non-polar diradical structure.

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Section: Resultsmentioning

confidence: 99%

Chiroptical Properties and the Racemization of Pyrene and Tetrathiafulvalene-Substituted Allene: Substitution and Solvent Effects on Racemization in Tetrathiafulvalenylallene

et al. 2014

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“…Allene 3a was also synthesized in enantiomerically pure form by HPLC separation of the enantiomers of precursor 2a (DIACEL Chiracel OD) and reaction of the enantiomerically pure propargyl acetates with t BuCu(CN)Li 15. The allenes (+)‐ 3a (99 % ee ) and(–)‐ 3a (>99 % ee ) thus obtained have unstructured CD spectra with a single band at 310 nm (see Supporting Information);16 the absolute configuration could not be determined so far.…”

Section: Resultsmentioning

confidence: 99%

Synthesis and Complexation Properties of Allenic Bipyridines, a New Class of Axially Chiral Ligands for Transition Metal Catalysis

et al. 2008

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The allenic bipyridines 3, which represent a new class of axially chiral ligands for transition metal catalysis, were synthesized and their complexation properties were studied. The synthesis was achieved by copper-mediated or palladiumcatalyzed S N 2Ј-substitution of the tertiary propargyl acetates 2. The allenic bipyridines form 1:1 complexes with Cu + and Ag + ions that were characterized by electrospray mass spec-

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“…The UV/Vis absorption and circular dichroism (CD) spectra of 16 in a solution of chloroform were recorded and are illustrated in Figures 2 and 3, respectively. There are very few reported examples of UV/Vis and CD spectra of cyclic allenes with which to compare the spectra of our acetylenic allenophane 24. Nevertheless, the typical “fingerprint” pattern for acetylenes with bands at 295, 313, and 335 nm is apparent in the UV/Vis spectrum.…”

Section: Methodsmentioning

confidence: 98%

Acetylenic Allenophanes: An Asymmetric Synthesis of a Bis(alleno)‐bis(butadiynyl)‐meta‐cyclophane

Clay

Fallis

2005

Angewandte Chemie

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We have an ongoing interest in the design and synthesis of novel cyclophanes, many of which contain a twisted conformation that imparts helical chirality [1] to the assembled molecule.[2] This helical chirality is a consequence of the number, type, and combination of unsaturated linkages present in these molecules. The synthesis and design of cyclophanes [3] and cage compounds with high carbon content in novel shapes and supramolecular geometries [4] continues to be a topic of current interest.Allenes are a unique family of organic molecules because of their diverse chemistry, axial chirality, and synthetic versatility, [5] and so investigations into allene-containing natural products and their total syntheses continue to increase.[6] Furthermore, medical applications for these compounds include employing them as inactivators of monoamine oxidase. [7] In contrast, cyclophanes that have only allene bridges (termed allenophanes) [8] have received little attention and the only reported example was prepared as a mixture of diastereomers.[8] A related family of cyclophanes comprises structures that contain both allene and acetylene bridges. These acetylenic allenophanes should also possess interesting properties. Herein, we report the first asymmetric synthesis of an acetylenic allenophane that contains two allene bridges. This compound appears to be the first cyclophane of this general class.The general structure of an acetylenic allenophane is depicted in Scheme 1. The R 1 substituents aid solubility: the absence of similar groups in the previously prepared allenophane [8] limited its solubility and prevented a full investigation into its properties. The R 2 substituents may be hydrogen atoms or alkyl groups, depending on the method selected to synthesize the allene moiety. The number of acetylene bridges may also be varied.We devised a strategy to an acetylenic allenophane related to 16 based on the dimerization of desilylated 15 (see Scheme 4). We [9a] and others [9b] observed previously that the separation of the alkyne termini dictates whether the intra-or intermolecular product dominates. Molecular modeling studies have strongly suggested that the intermolecular product is favored when the termini separation is greater than 7 .[9c] In the case of 15, the calculated alkyne separation of 8.87 [10] indicated that the intramolecular product 16 should be preferred.We initially examined the allene preparation used by Myers and Zheng for the synthesis of an allenophane in which R 2 groups are hydrogen atoms (Scheme 1). [11] This asymmetric method had the advantage that the allene precursor, a secondary propargyl alcohol, was readily available through the addition of an acetylide to an aldehyde.[12] Initially, orthoamino substituents at the aryl ring were chosen to aid solubility, but this idea had to be abandoned because electron donation from the lone pair of electrons on the nitrogen atom in the ortho-amino substituent leads to the formation of cumulene-type intermediates during allene formation (Scheme 2), and so...

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Enantioselective Synthesis and Circular Dichroism of Endocyclic Allenes

Cited by 25 publications

References 16 publications

Chiroptical Properties and the Racemization of Pyrene and Tetrathiafulvalene-Substituted Allene: Substitution and Solvent Effects on Racemization in Tetrathiafulvalenylallene

Chiroptical Properties and the Racemization of Pyrene and Tetrathiafulvalene-Substituted Allene: Substitution and Solvent Effects on Racemization in Tetrathiafulvalenylallene

Synthesis and Complexation Properties of Allenic Bipyridines, a New Class of Axially Chiral Ligands for Transition Metal Catalysis

Acetylenic Allenophanes: An Asymmetric Synthesis of a Bis(alleno)‐bis(butadiynyl)‐meta‐cyclophane

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