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.