Abstract
Here we report the design, preparation, synthetic utility, and sensing application of a class of proaromatic structures, namely bicyclo[2.2.0]hexene (BCH) derivatives. Building on a valence isomerism concept, they feature modular and easy synthesis as well as high thermal stability, and can be oxidatively activated under mild conditions. New alkyl transfer reactions using BCHs as a radical donor have been developed to showcase the utility of their proaromaticity. Moreover, the redox-triggered valence isomerization of a quinoline-derived BCH led to colorimetric and fluorescent responses toward vapors of electrophilic reagents in solution and solid phase, respectively. This optical response was shown to involve a 1,3-cyclohexadiene structure that possesses an intramolecular charge transfer excited state with interesting aggregation induced emission (AIE) character. Thus, the potential of BCHs has been demonstrated as a versatile platform for the development of new reagents and functional materials.
Highlights
We report the design, preparation, synthetic utility, and sensing application of a class of proaromatic structures, namely bicyclo[2.2.0]hexene (BCH) derivatives
Seeking an alternative strategy for proaromatic CHD activation under mild conditions, we proposed to take advantage of the low oxidation potential of alkylated 1,3-CHDs, which allows for activation by single electron transfer (SET) (Fig. 1b)[25,26,27,28,29]
Bicyclo [2.2.0]hexene carboxylic ester 1 was synthesized in multigram scale by the Diels-Alder reaction between an in situ formed cyclobutadiene and methyl acrylate with excellent endoselectivity[31]
Summary
We report the design, preparation, synthetic utility, and sensing application of a class of proaromatic structures, namely bicyclo[2.2.0]hexene (BCH) derivatives. The redox-triggered valence isomerization of a quinoline-derived BCH led to colorimetric and fluorescent responses toward vapors of electrophilic reagents in solution and solid phase, respectively This optical response was shown to involve a 1,3cyclohexadiene structure that possesses an intramolecular charge transfer excited state with interesting aggregation induced emission (AIE) character. Oestreich has demonstrated that 1,3-CHD and 1,4-CHD can be activated through hydride abstraction by a Lewis acid to form a Wheland intermediate II Based on this strategy, a broad spectrum of ionic group transfer reactions have been disclosed[15,16,17,18,19,20]. We report our study on the synthesis and properties of BCH derivatives Their synthetic utility as proaromatic radical donors is demonstrated in redox-triggered group transfer reactions. An interesting aggregation induced emission (AIE) behavior was found in this system (III′)
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
