Recent advances in radical thiocyanation cyclization or spirocyclization reactions

Abstract

Organic thiocyanates are valuable biology and drug-building blocks, which also can effectively transform into thioethers, thiols, alkynyl thioethers, thiocarbamates, et al in synthetic chemistry. Concerning the merits of thiocyanates, many...

C‐Centered radical intermediates for C(sp3)‐H bonds functionalization: An emerging approach towards alkyl thiocyanates

“…During the last decades, efforts have been devoted to the development of new methods to access this class of products, which have been the subject of several reviews over the years. [15][16][17][18][19][20][21][22][23][24] The synthesis of alkyl thiocyanates is of particular interest, since most of the SCN-containing bioactive compounds identified to date have an SCN moiety on a C(sp 3 ) center (Scheme 1A). The main strategies to access these derivatives have long been based on reactions using (a) SCN nucleophiles (typically thiocyanate salts) and (b) cyanation reagents in reaction with sulfur-containing compounds (e. g. thiols and disulfides).…”

“…[45] Several radical thiocyanation reactions have been reported to access alkyl thiocyanates (Scheme 2). [22,24] Most of them were based on the difunctionalization of carbon-carbon double bonds and allowed the incorporation of a second functional group at the adjacent position of the thiocyanate moiety (Scheme 2A). [20,22] These transformations involved either the generation of a * SCN radical from a thiocyanate anion (in the presence of K 2 S 2 O 8 , [46][47][48] O 2 , [49] CAN, [50] a photoredox catalyst [51][52][53] or silver pyridinium [54] ) and its Giese-like addition to an alkene (Method 1) [55] or the formation of C-centered radical intermediates by addition of another radical ( * Y = * CF 3 or * P(O)Ph 2 ) to the alkene and the subsequent copper-catalyzed thiocyanation (Method 2).…”

Visible Light-Induced Copper-Catalyzed Regio- and Stereoselective Difluoroalkylthiocyanation of Alkynes

“…As part of our continuing interest in the chemistry of di­(mono)­fluoroalkylation, we herein report a visible light-induced copper-catalyzed regio- and stereoselective difluoroalkylthiocyanation of alkynes with BrCF 2 R and KSCN to afford CF 2 -derived multisubstituted alkenes (Scheme d). The photosensitizer formed in situ from copper and a phosphine ligand not only promotes the generation of CF 2 -alkyl radicals but also aids in the formation of C–SCN bonds, allowing the reaction to proceed smoothly in the absence of any additional photocatalysts and radical initiators. Various CF 2 -alkyl radical precursors could be utilized to provide diverse β-fluoroalkyl vinyl thiocyanates with specific regio- and stereochemistry.…”