A Highly Regioselective Cyanothiolation of Alkynes via Oxidative Addition of Thiocyanates to Tetrakis(triphenylphosphine)palladium(0) Catalyst

Abstract

Tetrakis(triphenylphosphine)palladium(0) catalyzes the highly regioselectiVe addition of phenyl thiocyanate (PhSCN) to terminal alkynes, which attains the simultaneous introduction of thio and cyano groups to the internal and terminal positions of alkynes, respectiVely. This reaction may proceed Via the oxidatiVe addition of PhSCN to Pd(PPh 3 ) 4 , which forms Pd-(SPh)(CN)(PPh 3 ) 2 as the key intermediate.

The Formation of Csp 2 S and Csp 2 Se Bonds by Substitution and Addition Reactions Catalyzed by Transition Metal Complexes

“…In all of the studied cases the preferred regioselectivity of the addition reaction was to form the R (R 0 S)C¼CHX products (X ¼ B, P, Si, Ge). The same mechanism was proposed in the cyanothiolation of alkynes with PhSCN in the Pd(PPh 3 ) 4 -catalyzed reaction (120 C, 66 h,PhH) [133]. The intermediate transPd(SPh)(CN)(PPh 3 ) 2 complex was isolated from the corresponding stoichiometric reaction and the complex led to the same product -Z-(PhS)RC¼CH(CN) -as compared with the catalytic reaction.…”

Organometallic Approaches to Carbon–Sulfur Bond Formation

“…Thus, the use of thioesters represents a considerable advance in carbothiolation. Similar is the case with disulfides, vinylsulfides, thiocyanates, and allylic sulfides in carbothiolation type processes [157,158,179,235]. …”

“…A wide variety of sulfur derivatives can be used in these processes producing an array of interesting synthetic intermediates. These organosulfur compounds can be: free thiol [164, 167-170, 175, 190, 193, 197, 202, 204], disulfide [160,165,183,207], thiocyanate [179,182,186], thioborate [161], thiostannane [196], sulfenamide [180], and thioester [187,189,191,194,195]. Palladium catalyzed thiocarbonylation, and the development of multicomponent reactions centering on hydrothiolation with free thiols and disulfides has been reviewed extensively [19, 20, 23-26, 167, 227-231].…”

Catalytic Dicyanative 5‐exo‐ and 6‐endo‐Cyclization Triggered by Cyanopalladation of Alkynes

“…The introduction of a cyano function into simple and non-activated carbon/carbon triple bonds has been one of the most significant issues in synthetic organic chemistry, and nickel and palladium catalysts that enable cyanation with the introduction of H, [1] Si, [2] Ge, [3] Sn, [4] S, [5] C [6,7] and B [8] functionalities have been useful. Usually, a cyano group is installed by Ni-and Pd-catalysis through reductive elimination from an alkenyl À M À CN species, which gives alkenyl À CN together with M(0) (Scheme 1).…”