Palladium‐Catalyzed CH Fluorosilylation of 2‐Phenylpyridines: Synthesis of Silafluorene Equivalents

Abstract

Treatment of 2-phenylpyridines with amino(1,3,2-dioxaborolan-2-yl)diphenylsilane produced fluorosilylated 2-phenylpyridines in good to excellent yields under palladium catalysis. This reaction is the first example of C-H fluorosilylation. Single-crystal X-ray structure analysis revealed a Lewis acid-base interaction between the silicon and nitrogen atoms, and the obtained fluorosilylated products are silafluorene equivalents. The fluorosilylated products showed stronger fluorescence than the corresponding silafluorene derivative.

Ir-Catalyzed Enantioselective, Intramolecular Silylation of Methyl C–H Bonds

“…A KIE of 1.9 ± 0.1 was obtained from this set of experiments. This value is similar to that observed in our previous Ir-catalyzed silylation of secondary C(sp 3 )–H bonds (2.0 ± 0.1) 7h and Rh-catalyzed silylation of cyclopropyl C–H bonds (2.1 ± 0.1) 14 and implies that C–H cleavage is likely the rate-determining step of the reaction. 19 …”

“…Although progress on the silylation of both aromatic and aliphatic C–H bonds has been made over the past two decades, 7,8 the development of enantioselective variants of these reactions, particularly enantioselective silylation of unactivated C(sp 3 )–H bonds, has been limited (Scheme 1). 9 In 2013, Takai, Kuninubu, and co-workers published the first enantioselective silylation of aromatic C–H bonds.…”

“…Iridium complexes containing chelating, N,N -donor ligands, which have shown the most favorable combination of reactivity and functional group-compatibility in our studies in the C–H silylations, 7f,h,i had not been applied to the enantioselective silylation of C–H bonds until our recent work on Ir-catalyzed silylation of aromatic C–H bonds to form diarylmethanols. 15 …”

“…Product 2v was then subjected to conditions that convert the C(sp 2 )–Si bond to C–O, C–Cl, C–Br, and C–I bonds, giving products 3 – 6 in 81–98% yields. 1b,c,7d,e …”

The Development of Novel C-H Bond Transformations and Their Application to the Synthesis of Organic Functional Molecules

“…3a,4 We also achieved palladium catalyzed synthesis of sila uorene equivalents containing a Lewis acid base interaction by C H uorosilylation of 2 phenylpyridine derivatives (Scheme 21). 33 The uorosilylated 2 phenylpyridines were uorescent and the uorescent quantum yield was 0.50 (Scheme 21). For expression of the uorescence, the Lewis acid base interaction between silicon and nitrogen atoms is indispensable.…”