Highly Regio‐ and Stereoselective Hydrosilylation of Internal Thioalkynes under Mild Conditions

Abstract

Scheme 1. Backgroundt oalkyne hydrosilylation. Si stands for as ilyl group of the type R 3 Si;EWG = electron-withdrawing group.

Iridium-catalyzed Markovnikov hydrosilylation of terminal alkynes achieved by using a trimethylsilyl-protected trihydroxysilane

“…Propargyl ether analogues of menthol, carveol, prolinol, glucose and glucofuranose were successfully transformed into corresponding α-vinylsilanes in good to excellent yields (30-34). Other propargyl ethers derived from quinine, estrone, testosterone, cholesterol, and vitamin E could be effectively hydrosilylated as well, providing desired products with outstanding α regioselectivity (35)(36)(37)(38)(39). It is worthwhile to note that though terminal alkynyl derivatives from nitrogenous bases, theobromine, uridine, and phenylalanine showed poor solubility in acetonitrile, this protocol is well applicable in Markovnikov hydrosilylation of them as well (40)(41)(42)(43)(44)(45)(46).…”

“…The bulky (TMSO) 3 SiH, which is easily prepared from HSiCl 3 and (TMS) 2 O, was chosen as the silane partner to verify our anticipation. It is noteworthy that though in contrast with the wide utilization of Et 3 SiH, (EtO) 3 SiH and other common hydrosilanes in hydrosilylation of unsaturated molecules, examples that use (TMSO) 3 SiH as hydrosilane source are still limited [58][59][60][61][62][63][64] , it showed its unique function in promoting the reaction selectivity 63 or inducing different selectivities 64 . Several simple iridium catalysts were tested firstly under a mild condition (entry 1-4).…”

“…3). Considering the widespread hydroxyl and amino groups in biomolecules, propargyl derivatives from them were selected as representatives in most cases (30)(31)(32)(33)(34)(35)(36)(37)(38)(39)(40)(41)(42)(43)(44)(45). Propargyl ether analogues of menthol, carveol, prolinol, glucose and glucofuranose were successfully transformed into corresponding α-vinylsilanes in good to excellent yields (30-34).…”

“…1 H and 13 C NMR Spectra of all hydrosilylation products and unknown substrate were provided. 13 C DEPT135 NMR Spectra of products 3,4,5,6,7,9,10,12,13,15,19,20,21,26,30,31,32,36,37,38,39,40,41,42,44,45 were afford. 2D NOESY Results of products 1 and 27 are also provided.…”

“…1b) [19][20][21][22] . By contrast, exploitation of suitable hydrosilanes to achieve α regioselectivity under simple catalysis has been rarely studied 36 . Hydrosilanes with bulkier substituents are presumed to have lower reactivity, which might allow the coordination of the metal center with the alkyne to go first, leading the process to follow the Wu-Trost mechanism and bring α-vinylsilane adducts ( Fig.…”