Cu(I)-Catalyzed 6-endo-dig Cyclization of Terminal Alkynes, 2-Bromoaryl Ketones, and Amides toward 1-Naphthylamines: Applications and Photophysical Properties

Abstract

Functional group substituted 1-naphthylamines, especially N-methylated ones, play important roles in numerous chemical and biological processes. However, these compounds' general and stepeconomic syntheses are highly limited, which seriously restricts efforts to improve the properties and develop new functions for this kind of compound. In this report, we describe the development of an efficient, convenient, and general method for the synthesis of valuable functionalized 1-naphthylamines directly from readily available terminal alkynes, 2-bromoaryl ketones, and amides via Cu(I)-catalyzed benzannulation in a green solvent (i.e., water) under Pd-and ligand-free conditions. A total of 82 functionalized 1naphthylamines, especially synthetically and biologically useful N-methylated compounds, are synthesized in isolated yields up to 95%. Some unique features of the reaction are as follows: (1) exclusive 6-endo-dig selectivity, (2) ready incorporation of a broad range of functional groups directly from easily available substrates, and (3) amides that can be used as aminating agents and that are excellent alternatives to toxic and/or odorous amines. Due to facile tuning of functional groups for the reaction, the products possess good electronic donor−acceptor structures and exhibit intriguing photophysical properties, such as tunable and polarity-sensitive fluorescence emission and large Stokes shifts (up to 258 nm). Utilizing the products' unique polaritysensitive fluorescence response, we successfully applied the 1-naphthylamine derivatives, such as compound 91, to image lipid droplets (LDs) and monitor cellular LDs growth. The previously mentioned advantages of this methodology, along with the mild conditions, simple operation, and scalable synthesis, may allow this novel reaction to be extended to varied applications in chemistry, biology, and materials science.

Fluorescent amino acids as versatile building blocks for chemical biology

“…Similarly, the emergence of new chemistry in the field of synthetic fluorophores will enable the construction of FlAAs with additional properties. These properties include not only physicochemical properties, such as small size 158,159 to reduce the effect of labelling in peptides and proteins, but also optical features for spectroscopy and imaging experiments, including near-infrared emission 160,161 , superresolution capabilities 162,163 , photoactivatable behaviour 164,165 or suitability for multimodal imaging (for example, optoacoustics and positron emission tomography) 166,167 . A greater number and variety of FlAAs will create avenues to identify new roles for peptides and proteins in biological systems.…”

Multifunctional Gold Nanoparticles@Imidazolium-Based Cationic Covalent Triazine Frameworks for Efficient Tandem Reactions

“…It is well known that arylamines containing multifunctional groups are one key class of intermediates in synthesizing dyes and drugs such as the widely used antiinflammatory drug acetaminophen. [8][9][10] Generally, the synthesis of such substances require multistep reactions. 11,12 Therefore, developing multifunctional tandem catalyst systems with multiple active sites to synthesize such chemical compounds is highly desirable.…”

Copper‐mediated simple and direct aerobic oxidative esterification of arylacetonitriles with alcohols/phenols

“…Herein, as a part of our ongoing research in copper catalysis, [ 10 ] we report a simple and direct aerobic oxidative esterification of easily available arylacetonitriles with alcohols/phenols mediated by simple copper salt (Scheme 1). This procedure successfully combines inert CC bond cleavage, [ 11,12 ] CH bond oxygenation, and CO bond formation in one pot from readily available starting materials without the need for any of the acids, bases, ligands, and so on and produces a broad range of aryl carboxylic acid esters in good to high yields.…”