Photochromic derivatives of indigo: historical overview of development, challenges and applications

• Gökhan Kaplan,
• Zeynel Seferoğlu and
• Daria V. Berdnikova

Beilstein J. Org. Chem. 2024, 20, 228–242, doi:10.3762/bjoc.20.23

• derivatives, outline the structural peculiarities, photophysical and photochemical properties of indigo and proceed with the detailed discussion of the photochromic indigo derivatives. Finally, we highlight the photochromism of the structural isomers of indigo (isoindigo and indirubin) and provide an overview

• the considerably longer thermal half-lives of Z-22b and Z-23c in comparison to Z-23d [45]. Photochromism of the structural isomers of indigo The indigo dye has two naturally occurring structural isomers, indirubin (26) and isoindigo (27), which differ in the attachment pattern of the two indole rings

• of the indirubin photoswitches took place upon irradiation of deep red light (730 nm). Another structural isomer of indigo, the brown-colored isoindigo (27), was first synthesised by Laurent in 1842 [73]. Along with indigo and indirubin, isoindigo can be found in minor amounts in the leaves of Isatis

Recent advances in the application of isoindigo derivatives in materials chemistry

• Andrei V. Bogdanov and
• Vladimir F. Mironov

Beilstein J. Org. Chem. 2021, 17, 1533–1564, doi:10.3762/bjoc.17.111

• Andrei V. Bogdanov Vladimir F. Mironov A.E. Arbuzov Institute of Organic and Physical Chemistry, FRC Kazan Scientific Center of RAS, 8 Arbuzov St., Kazan 420088, Russian Federation 10.3762/bjoc.17.111 Abstract In this review, the data on the application of isoindigo derivatives in the chemistry

• of functional materials are analyzed and summarized. These bisheterocycles can be used in the creation of organic solar cells, sensors, lithium ion batteries as well as in OFET and OLED technologies. The potentials of the use of polymer structures based on isoindigo as photoactive component in the

• photoelectrochemical reduction of water, as matrix for MALDI spectrometry and in photothermal cancer therapy are also shown. Data published over the past 5 years, including works published at the beginning of 2021, are given. Keywords: isoindigo; OFET; photoactive polymers; photovoltaics; solar cells; Introduction

Synthesis of (Z)-3-[amino(phenyl)methylidene]-1,3-dihydro-2H-indol-2-ones using an Eschenmoser coupling reaction

• Lukáš Marek,
• Lukáš Kolman,
• Jiří Váňa,
• Jan Svoboda and
• Jiří Hanusek

Beilstein J. Org. Chem. 2021, 17, 527–539, doi:10.3762/bjoc.17.47

• complete decomposition giving mainly the isoindigo derivatives 9a–e. Similar issues were observed when the secondary or tertiary thiobenzamides 3a–i or 4a–c were used. The following Scheme 2 summarizes the main possible reaction routes starting from 3-bromooxindoles 1a–e and various primary, secondary, and

• carbanion, such a base also converts the reactive α-thioiminium group to a much less reactive thioimidate at the same time. The C3 carbanion then preferentially attacks (route c) another molecule of the starting material 1a–e and the resulting adducts undergo a subsequent elimination to give the isoindigo

• high amounts of the undesirable isoindigo 9a [32] (route c). In order to accelerate the Eschenmoser coupling reaction and to enhance the reaction yield (route b) an addition of a suitable thiophile assisting the sulfur extrusion should be beneficial [36]. Therefore, we tested two P(III) compounds as

All-carbon [3 + 2] cycloaddition in natural product synthesis

• Zhuo Wang and
• Junyang Liu

Beilstein J. Org. Chem. 2020, 16, 3015–3031, doi:10.3762/bjoc.16.251

• isoindigo 100 was used as substrate, enantioselective [3 + 2] annulation with allene 101 in the presence of amino acid-derived bifunctional phosphine 102 produced adduct 103 in 90% yield with 92% ee and 4:1 regioisomeric ratio (rr). The authors suggested that the observed regioselectivity could be

• rationalized by the proposed catalytic mechanism (Scheme 7B). The phosphine (i.e., PR3, A) attacks the allene 101 to generate zwitterion intermediate B, which is subjected to a less hindered attack by the isoindigo 100. The oxindole bearing a chlorine atom on isoindigo 100 makes C-3 more electron deficient

• -workers applied the enantioselective [3 + 2] annulation to complete the formal synthesis of (−)-ditryptophenaline (12) [46] (Scheme 7C). The synthesis began with the catalytic asymmetric [3 + 2] annulation of symmetric isoindigo 104 and allene 101 with chiral phosphine catalyst 102 to give spirocyclic