A NEW REAGENT FOR RESOLUTION BY COMPLEX FORMATION; THE RESOLUTION OF PHENANTHRO-[3,4-c]PHENANTHRENE<sup>1</sup>

Newman, Melvin S.; Lutz, Wilson B.; Lednicer, Daniel

doi:10.1021/ja01617a097

Cited by 151 publications

(102 citation statements)

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“…Thus, the structures 4 [12], 5 [13,14], and 6 [15,16], are [4]helicene, [5]helicene, and [6]helicene, respectively ( Figure 1). However, any fused ring which is not present in the ortho-fused manner is not included in the n counting.…”

Section: Carbohelicenesmentioning

confidence: 99%

“…The early pioneering work on helicene synthesis, resolution, and chiroptical properties has been performed by Newman [15,16,41], Wynberg [36,38], Martin [42], and Katz [26]. In general, classical methods of helicene synthesis include the following approaches: oxidative photocyclization, Diels-Alder reactions, and various aromatic and metal-catalyzed coupling reactions [2][3][4][5][6]11].…”

Section: General Description and Main Synthetic Approaches Toward Helmentioning

confidence: 99%

“…The major methods of obtaining enantiopure helicenes from a racemic mixture are based on optical resolution by chiral HPLC [60,77,78,83,101], diastereomeric salt formation [51,60,76] (for representative resolving agents, see Figure 22), chromatographic separation of diastereomers [52,56,74], and enzymatic-based approaches [97]. For example, racemic nonfunctionalized helicenes were successfully resolved through charge transfer complexation with electron-deficient molecules, such as TAPA [15,16] or HPLC-based separation with the use of silica coated with TAPA [106]. In the case of functionalized helicenecontaining phenolic groups at the terminal ring, (1S)-camphanic chloride acts as the best resolving agent for chromatographically separable diastereomers obtained.…”

Section: Enantiopure Helicenes: Enantioselective Synthesis Chiral Sementioning

confidence: 99%

“…However, the absolute configuration of the 2-ethylhexyl alkyl chain was not discussed in the paper [108]. For example, racemic nonfunctionalized helicenes were successfully resolved through charge transfer complexation with electron-deficient molecules, such as TAPA [15,16] or HPLC-based separation with the use of silica coated with TAPA [106]. In the case of functionalized helicenecontaining phenolic groups at the terminal ring, (1S)-camphanic chloride acts as the best resolving agent for chromatographically separable diastereomers obtained.…”

Section: Enantiopure Helicenes: Enantioselective Synthesis Chiral Sementioning

confidence: 99%

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Helicene-Based Chiral Auxiliaries and Chirogenesis

Hasan

Borovkov

2017

Symmetry

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Helicenes are unique helical chromophores possessing advanced and well-controlled spectral and chemical properties owing to their diverse functionalization and defined structures. Specific modification of these molecules by introducing aromatic rings of differing nature and different functional groups results in special chiroptical properties, making them effective chiral auxiliaries and supramolecular chirogenic hosts. This review aims to highlight these distinct structural features of helicenes; the different synthetic and supramolecular approaches responsible for their efficient chirality control; and their employment in the chirogenic systems, which are still not fully explored. It further covers the limitation, scope, and future prospects of helicene chromophores in chiral chemistry.

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Section: Carbohelicenesmentioning

confidence: 99%

Section: General Description and Main Synthetic Approaches Toward Helmentioning

confidence: 99%

Section: Enantiopure Helicenes: Enantioselective Synthesis Chiral Sementioning

confidence: 99%

Section: Enantiopure Helicenes: Enantioselective Synthesis Chiral Sementioning

confidence: 99%

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Helicene-Based Chiral Auxiliaries and Chirogenesis

Hasan

Borovkov

2017

Symmetry

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“…* Discussion. 2-(2,4,5,7-Tetranitro-9-fluorenylidene)propionic acid (TAPA) (1), which was first employed in the separation of enantiomers of hexahelicene (Newman, Lutz & Lednicer, 1955;Newman & Lednicer, 1956), has since proved to a valuable reagent for the optical resolution of certain aromatic compounds (e.g. racemic Lewis bases), especially those which do not have the functional groups usually needed to effect resolution by conventional reagents.…”

Section: Ui2mentioning

confidence: 99%