Two‐Step Synthesis of Blue Luminescent (Pyrrol‐3‐yl)‐1H‐(aza)indazoles Based on a Three‐Component Coupling–Cyclocondensation Sequence. Issue 23 (8th July 2015)

• Record Type: Journal Article
• Authors: Nordmann, Jan; Eierhoff, Svenja; Denißen, Melanie; Mayer, Bernhard; Müller, Thomas J. J.
• Is Part Of: European journal of organic chemistry. Issue 23(2015)
• Page Start: 5128
• Page End: 5142
• Publication Date: 2015-07-08
• Subjects: Synthetic methods -- Luminescence -- Nitrogen heterocycles -- Alkynes; Chemistry, Organic -- Periodicals; Organic compounds -- Synthesis -- Periodicals; Bioorganic chemistry -- Periodicals; Chemistry, Physical organic -- Periodicals; 547
• DOI: 10.1002/ejoc.201500575
• Languages: English
• ISSNs: 1434-193X

Abstract

Abstract: (Pyrrol‐3‐yl)‐1 H ‐(aza)indazoles can be efficiently prepared by a two‐step process that consists of a consecutive three‐component coupling–cyclocondensation synthesis to give ortho ‐halo‐3‐acylpyrrol‐3‐yl‐substituted (hetero)arenes followed by a cyclization–condensation–SN Ar sequence. Almost all derivatives display an intense blue emission upon excitation in the near UV with enormous Stokes shifts (6500–8300 cm –1 ) and considerable high fluorescence quantum yields ( Φf = 0.28–0.46). Electronic transitions can be plausibly rationalized by TD‐DFT computations performed on DFT‐optimized geometries. Reversible protonation leads to static fluorescence quenching in narrow pH‐ranges, which qualifies the title compounds as favorable ON/OFF fluorescence switching systems. Abstract : A consecutive three‐component synthesis for ortho ‐halo‐3‐acylpyrrol‐3‐yl‐substituted (hetero)arenes followed by a cyclization–condensation–SN Ar sequence opens an efficient modular approach to blue luminescent (pyrrol‐3‐yl)‐1 H ‐(aza)indazoles.