One‐Pot Copper‐Catalyzed Cascade Bicyclization Strategy for Synthesis of 2‐(1H‐Indol‐1‐yl)‐4,5‐dihydrothiazoles and 2‐(1H‐Indol‐1‐yl)thiazol‐5‐yl Aryl Ketones with Molecular Oxygen as an Oxygen Source

Abstract

An atom-economical method for synthesizing N-heterocyclic indoles from readily available o-alkynylphenyl isothiocyanates and propargylamine derivatives is reported. This method involves a copper-catalyzed cascade bicyclization process consisting of an intramolecular 5-exo-dig hydrothiolation reaction and an intramolecular hydroamination reaction and, depending on whether or not molecular oxygen is present, selectively affords Z-isomers of 2-(1H-indol-1-yl)-4,5-dihydrothiazoles or 2-(1H-indol-1-yl)thiazol-5-yl aryl ketones in satisfactory yields. Mechanistic studies indicate that molecular oxygen acts as the oxygen source for the ketone moiety in the products.

Substrate-Controlled Cu(OAc)2-Catalyzed Stereoselective Semi-Reduction of Alkynes with MeOH as the Hydrogen Source

“…The crude product was purified by flash column chromatography (eluted with petroleum ether/ethyl acetate = 5/1–3/1) on silica gel to afford internal alkyne product 1 . The characterization data of 1a , 20 1b , 21 1d , 20 1e , 22 1h , 23 1i , 24 and 1l ( 25 ) were consistent with the reported literature.…”

Development of a Telescoped Flow Process for the Safe and Effective Generation of Propargylic Amines

“…Such a process was expected to yield valuable heterocyclic derivatives via intermediate thiourea adducts 12 that would cyclize in an acid-catalyzed reaction cascade. This sequence is interesting as it allows direct access to either thiazoline or thiazole derivatives 13 or 14 as reported in the literature [33,34,35,36,37]. We were specifically interested in selectively generating thiazoline species as these provide an exocyclic alkene that can serve as a handle for accessing highly functionalized derivatives (Figure 1).…”

Base-promoted cyclization reaction of o-isothiocyanato arylacetylenes and aroylacetonitriles: easy access to benzo[d][1,3]thiazines

“…3 d In 2018, Wang's group built 2-(1 H -indol-1-yl)-4,5-dihydrothiazoles by means of a copper-catalyzed cascade bicyclization reaction of o -alkynylphenyl isothiocyanates with propargylamines. 10 Notwithstanding these successes, o -alkynylphenyl isothiocyanates serving as powerful and versatile building blocks still possess great value. In addition, the reaction of o -alkynylphenyl isothiocyanates with nucleophiles under transition-metal-free conditions has not been reported to date.…”