Allenes in Molecular Materials

Rivera‐Fuentes, Pablo; Diederich, François

doi:10.1002/anie.201108001

Cited by 382 publications

(184 citation statements)

References 103 publications

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“…We now know that allenes are widely distributed in nature and featured as key structural elements in a diverse range of natural products, bioactive small molecules, and materials. 5,6 Allenes are highly versatile intermediates for synthesis, participating in numerous powerful chemical transformations. 7,8 The development of methods for the concise synthesis of allenes has therefore been an area of intense research for many years.…”

Section: Introductionmentioning

confidence: 99%

Enantioselective Synthesis of Allenes by Catalytic Traceless Petasis Reactions

et al. 2017

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Allenes are useful functional groups in synthesis as a result of their inherent chemical properties and established reactivity patterns. One property of chemical bonding renders 1,3-substituted allenes chiral, making them attractive targets for asymmetric synthesis. While there are many enantioselective methods to synthesize chiral allenes from chiral starting materials, fewer methods exist to directly synthesize enantioenriched chiral allenes from achiral precursors. We report here an asymmetric boronate addition to sulfonyl hydrazones catalyzed by chiral biphenols to access enantioenriched allenes in a traceless Petasis reaction. The resulting Mannich product from nucleophilic addition eliminates sulfinic acid, yielding a propargylic diazene that performs an alkyne walk to afford the allene. Two enantioselective approaches have been developed; alkynyl boronates add to glycolaldehyde imine to afford allylic hydroxyl allenes, and allyl boronates add to alkynyl imines to form 1,3-alkenyl allenes. In both cases, the products are obtained in high yields and enantioselectivities.

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Section: Introductionmentioning

confidence: 99%

Enantioselective Synthesis of Allenes by Catalytic Traceless Petasis Reactions

et al. 2017

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“…They are also found in many natural products, pharmaceuticals [3] and molecular materials [4]. Thus, over the last decade, allenes have attained a prominent position in organic transformations like cycloaddition, cycloisomerization, base or metal-catalyzed reactions [5–7].…”

Section: Introductionmentioning

confidence: 99%

Allenylphosphine oxides as simple scaffolds for phosphinoylindoles and phosphinoylisocoumarins

Gangadhararao¹,

Kotikalapudi²,

Reddy³

et al. 2014

Beilstein J. Org. Chem.

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SummaryA range of phosphinoylindoles was prepared in one-pot from functionalized propargyl alcohols and a suitable P(III) precursor via a base-mediated reaction. The reaction proceeds via the intermediacy of allenylphosphine oxides. Similarly, phosphinoylisocoumarins were prepared from allenylphosphine oxides in a trifluoroacetic acid-mediated reaction; the latter also acts as a solvent. Interestingly, in the presence of wet trifluoroacetic acid, in addition to phosphinoylisocoumarins, phosphorus-free isocoumarins were also obtained. Key products were characterized by single crystal X-ray crystallography.

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“…22,29 This approach has been especially useful in producing expanded [4]radialenes 28,29 (i.e., Figure 1, 2 with m = 1) from acyclic iso-polydiacetylene (iso-PDA) precursors, 47 both in terms of yield and product stability. The successful synthesis of an expanded [4]radialene seemingly comes about through a balance achieved between ring strain present in a smaller expanded [3]radialene and the steric and/or entropic effects that challenge the formation of larger expanded [5]-and [6]radialenes. 29 With this in mind, expanded [4]radialenes were chosen as the 2D cross-conjugated framework for incorporating electron donors and acceptors.…”

Section: ■ Introductionmentioning

confidence: 99%

“…An analysis of selected [4]radialenes from this study has been done using cyclic voltammetry, and the results are shown in Table 3 (individual CV scans are provided in the Supporting Information). In general, oxidation potentials of derivatives containing dialkylaniline moieties are dictated by the donor groups, and each shows an irreversible event in the range of 0.3−0.4 V. In the absence of the aniline group (e.g., 5,18,19), the first oxidation potential is located at ca. 1.0−1.1 V, as reported for other expanded [4]radialene derivatives.…”

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confidence: 99%

Donor- and/or Acceptor-Substituted Expanded Radialenes: Theory, Synthesis, and Properties

et al. 2014

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ABSTRACT:The synthesis of donor-(D) and/or acceptor (A)-expanded [4]radialenes has been developed on the basis of readily available dibromoolefin (7), tetraethynylethene (10 and 20), and vinyl triflate (12) building blocks. The successful formation of D/A radialenes relies especially on (1) effective use of a series alkynyl protecting groups, (2) Sonogashira crosscoupling reactions, and (3) the development of ring closing reactions to form the desired macrocyclic products. The expanded [4]radialene products have been investigated by spectroscopic (UV−vis absorption and emission) and quantum chemical computational methods (density functional theory and time dependent DFT). The combined use of theory and experiment provides a basis to evaluate the extent of D/A interactions via the cross-conjugated radialene framework as well as an interpretation of the origin of D/A interactions at an orbital level. ■ INTRODUCTIONConjugated carbon-rich macrocycles are intriguing targets of study for both theoretical and experimental chemists because of their often symmetrical shape and aesthetically appealing structures. They are, however, useful molecules as well, with potential as the organic component for electronic, optical, and nonlinear optical applications.1−8 A specific subcategory of conjugated macrocycles are the [n]radialenes, which are cyclic, carbon-rich molecules with a general formula C 2n H 2n that contain n ring atoms and n exocyclic double bonds (1, Figure 1). "Expanded radialenes" are derivatives of radialenes that originate by formal insertion of an unsaturated spacer between each pair of exomethylene fragments of a radialene, giving rise to macrocycles such as 2 and 3 (Figure 1). 8−12 Work with expanded radialenes was pioneered by Diederich and co-workers 13−16 via the introduction of diacetylene moieties into the radialene framework to give derivatives with the general structure 3 17,18 as well as structurally related radiannulenes.19−27 More recently, expanded radialenes 2 composed of repeating enyne units have been realized and studied. 28−30The two-dimensionally (2D) conjugated structure of expanded [n]radialenes is rather special because it combines a number of linearly and cross-conjugated pathways placed on a nonbenzoid carbon framework.31−39 One key question concerning the properties of expanded [n]radialenes has been the role played by cross-conjugation 9,40,41 to the overall electronic makeup of these unique molecules. The influence of D−A or D/A interactions 42 via cross conjugation in acyclic systems has been explored by a number of groups. 9,10,43−46 To date, however, only a few examples of donor-or acceptor-expanded radialenes have been reported. 18,28 Finally, donor−acceptor-expanded radialenes remain unknown, and there have been no attempts to document cross-conjugated interactions in these derivatives using theory.Our group has recently reported a modular approach for the synthesis of perphenylated expanded [n]radialenes 29 and radiaannulenes. 22,29 This approach has been especially useful ...

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Allenes in Molecular Materials

Cited by 382 publications

References 103 publications

Enantioselective Synthesis of Allenes by Catalytic Traceless Petasis Reactions

Enantioselective Synthesis of Allenes by Catalytic Traceless Petasis Reactions

Allenylphosphine oxides as simple scaffolds for phosphinoylindoles and phosphinoylisocoumarins

Donor- and/or Acceptor-Substituted Expanded Radialenes: Theory, Synthesis, and Properties

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