Benzopentalenonaphthalenones from the intramolecular capture of a merocyanine derived from a naphthopyran

Abstract

Novel, highly coloured benzopentalenonaphthalenones result from a cascade process initiated by the thermally-induced ring-opening of diarylmethanol substituted 2H-naphtho[1,2-b]pyrans in the presence of acid.

Brønsted Acid Promoted Thermal‐Ring‐Rearrangement of Fluorenopyrans to 2‐(1H‐Inden‐3‐yl)‐9H‐fluoren‐3‐ols Bearing Two All‐Carbon‐Quaternary Centres

“…Ring‐rearrangement reactions are the ring‐opening‐cyclization of a single substrate by means of an acid/base or a metal catalyst under thermal conditions . These ring‐rearrangements involve a cascade of reactions that take place in a single‐pot with maximum atom economy (≈ 100 %) and hence fall under green chemical synthesis .…”

“…Particularly, the ring rearrangement reactions of benzochromene derivatives bearing a C2‐quaternary centre is depicted in Figure . For example, when naphthopyran [ IA ] was heated with a catalytic amount of p TsOH in toluene, it underwent an irreversible ring‐rearrangement to give highly coloured benzopentaleno‐naphthalenones [ IB ], however, there are only two examples described using this method . Later, 3‐(2‐ethoxyethyl)‐2,2‐diphenyl‐2 H ‐chromene [ IC ] was also underwent ring‐rearrangement with scandium triflate at 60 °C to furnish 2‐(3‐phenyl‐1 H ‐inden‐1‐yl)phenol [ ID ], but a single example was demonstrated using this method .…”

Preparation and photochromic properties of layer-by-layer self-assembly films and light-responsive micelles based on amphiphilic naphthopyran derivative

“…Until now, naphthopyran has not been studied in this particular field except in one of our report [14]. Most of research works on naphthopyran are based on modification of naphthopyran molecule with different functional groups [15][16][17] or incorporating naphthopyran into polymers in which the dyes are incorporated to modulate the fading rate of open-form NP [18][19][20]. Modification on naphthopyran molecules with different substitution groups is an adaptable strategy because it can change the intrinsic electronic nature or structure to further influence the fading speed.…”

Thermochromic and/or photochromic properties of electrospun cellulose acetate microfibers for application as sensors in smart packing

“…29 Spiropyrans are colorless, whose main characteristic is based on the molecular rearrangement by opening the pyrans ring, in the presence of UV rays, generating a colored photomericyanin molecule in yellow, orange, and red tones. 30 One of the techniques that have taken force in the production of this type of membranes is electrospinning. This is a technique capable of creating nanostructured mats, composed mainly of monolithic fibrous structures and/or core-shell, porous, hollow, and obtained from a polymeric solution applying an electric field.…”

“…The classification of it depends on the mechanism that allows color exchange 29 . Spiropyrans are colorless, whose main characteristic is based on the molecular rearrangement by opening the pyrans ring, in the presence of UV rays, generating a colored photomericyanin molecule in yellow, orange, and red tones 30 …”