Me3SiCl‐Catalyzed Electrophilic Thiocyanation/Cyclization of Alkynylbenzoates to Synthesize 4‐Thiocyanatoisocourmarins

Me3SiBr-promoted cascade electrophilic thiocyanation/cyclization of ortho-alkynylanilines to synthesize indole derivatives

A Lewis acid-promoted electrophilic thiocyanation/cyclization of ortho-alkynylanilines for the synthesis of indole derivatives has been developed. The reaction utilizes Me3SiBr as the Lewis acid and N-thiocyanatosuccinimide as the thiocyanation reagent. A series of 2-aryl-3-thiocyanato indoles were prepared in moderate to high yields under mild conditions without metals and oxidants. It provides an efficient protocol for the construction of the indole skeleton and C-SCN and C-N bonds in one step as well.

Synthesis of thiocyanato-containing phenanthrenes and dihydronaphthalenes via Lewis acid-activated tandem electrophilic thiocyanation/carbocyclization of alkynes

A tandem electrophilic thiocyanation and cyclization of arene-alkynes has been developed under mild conditions, affording thiocyanato-substituted phenanthrenes, dihydronaphthalenes, 2H-chromenes and dihydroquinolines in moderate to excellent yields. This reaction provides an efficient protocol for the construction of C-SCN and C-C bonds in one step. In this transformation, N-thiocyanato reagent serves as a convenient precursor to transfer SCN⁺ in the presence of trimethylchlorosilane, and the cyclization exhibited exclusive 6-endo-dig selectivity. Finally, a gram scale reaction and further derivatizations highlight the utility of this synthetic strategy.

Recent progress of direct thiocyanation reactions

Thiocyanates are common in natural products, synthetic drugs and bioactive molecules. Many thiocyanate derivatives show excellent antibacterial, antiparasitic and anticancer activities. Thiocyanation can introduce SCN groups into parent molecules for constructing SCN-containing small organic molecules. Among them, the direct introduction method mainly includes nucleophilic reaction, electrophilic reaction and free radical reaction, which can simply and quickly introduce SCN groups at the target sites to construct thiocyanates, and has broad application prospects. In this review, we summarize the research progress of direct thiocyanation in recent years.