Copper(I)-catalyzed cascade reaction of 2-haloaryl isothiocyanates with isocyanides: a strategy to construct benzo[d]imidazo[5,1-b]thiazoles

I2-mediated Csp2–P bond formation via tandem cyclization of o-alkynylphenyl isothiocyanates with organophosphorus esters

A highly efficient molecular-iodine-catalyzed cascade cyclization reaction has been developed, creating a series of 4H-benzo[d][1,3]thiazin-2-yl phosphonates in moderate to excellent yields. This approach benefits from metal-free catalysts and available raw materials.

Copper(i)-catalyzed tandem synthesis of 4,5-functionalized oxazoles from isocyanoacetate and aldehydes

Herein is developed a tandem reaction for the synthesis of a diverse array of 4,5-difunctionalized oxazoles utilizing easily-accessible ethyl 2-isocyanoacetate and aldehydes (26 examples, 31–83% yields).

Copper(ii)-catalyzed tandem cyclization for the synthesis of benzo[d][1,3]thiazin-2-yl phosphonates involving C-P and C-S bond formation

A copper(ii)-catalyzed, high-efficiency and atom-economical synthesis of valuable organophosphorus compounds via tandem cyclization of o-alkynylphenyl isothiocyanates with phosphites is described. This protocol, having a good functional-group compatibility, provides a simple and direct pathway to organophosphorus heterocycles in good yields under mild conditions. The method could be efficiently scaled up to gram scale, thus providing a potential application of this cascade cyclization strategy in synthesis.

A simple and highly efficient cascade cyclization of o-alkynylphenyl isothiocyanates with phosphites has been developed, affording a series of 4H-benzo[d][1,3]thiazin-2-yl phosphonates in moderate to good yields.

Tandem Catalysis: Synthesis of Nitrogen-Containing Heterocycles

In this Review, we consider all the publications since the beginning of the century that describe tandem reactions resulting in the formation of five-membered aromatic nitrogen heterocycles (thiazole, imidazole, indole, tetrazole, triazole, and isoxazole). The contents of this review are organized by taxonomy and type of tandem catalysis. It covers orthogonal, auto-, and assisted tandem catalysis, providing an overview of tandem reactions applied tonitrogen heterocycles reported in the literature up to March 2020. We believe that this compilation of data will provide a necessary starting reference to developthe applications of tandem catalysis in medicinal chemistry.

On water catalyst-free synthesis of benzo[d]imidazo[2,1-b] thiazoles and novel N-alkylated 2-aminobenzo[d]oxazoles under microwave irradiation

A highly efficient unprecedented catalyst-free microwave-assisted procedure for synthesizing benzo[d]imidazo[2,1-b]thiazoles and N-alkylated 2-aminobenzo[d]oxazol in green media was developed. The transformation provided rapid access to functionalized benzo[d]imidazo[2,1-b]thiazoles from 2-aminobenzothiazole and N-alkylated 2-aminobenzo[d]oxazole from 2-aminobenzoxazole scaffolds under mild transition-metal-free conditions. This synthetic manipulation is expected to greatly expand the repertoire of reaction types in heterocyclic chemistry and pave the way for new syntheses of bioactive compounds.

A highly efficient unprecedented catalyst-free microwave-assisted procedure for synthesizing benzo[d]imidazo[2,1-b]thiazoles and N-alkylated 2-aminobenzo[d]oxazol in green media was developed.

Synthesis of thiazolo[2,3-b]quinazoline derivatives via base-promoted cascade bicyclization of o-alkenylphenyl isothiocyanates with propargylamines

A highly efficient cascade bicyclization reaction of o-alkenylphenyl isothiocyanates with propargylamines has been developed, which affords a series of thiazolo[2,3-b]quinazolines in good to excellent yields by using K₂CO₃ as a base in MeCN at 80 °C. This method is transition-metal-free and operationally simple with broad functional group tolerance. Mechanistically, 6-exo-trig hydroamination followed by 5-exo-dig hydrothiolation was involved in this transformation.

A silver(i)-catalyzed cascade bicyclization strategy for synthesis of 5H-benzo[d]tetrazolo[5,1-b][1,3]thiazines

A simple and efficient protocol for silver(i)-catalyzed tandem reaction of o-alkynylphenyl isothiocyanates with sodium azide has been developed, affording a series of 5H-benzo[d]tetrazolo[5,1-b][1,3]thiazines in moderate to good yields. In this transformation, a [3 + 2] cycloaddition reaction mechanism was involved and two new rings were formed in one pot.