Room-temperature palladium-catalyzed direct 2-arylation of benzoxazoles with aryl and heteroaryl bromides

Abstract

An efficient room-temperature palladium-catalyzed direct 2-arylation of benzoxazoles with aryl bromides is presented. The Pd(OAc)2/NiXantphos-based catalyst enables the introduction of various aryl and heteroaryl groups, via a deprotonative cross-coupling process (DCCP) in good to excellent yields (75–99%).

Direct arylation of benzoazoles with aldehydes utilizing metal–organic framework Fe3O(BDC)3 as a recyclable heterogeneous catalyst

“…9 Walsh et al demonstrated a productive room-temperature Pd(OAc) 2 / NiXantphos-catalyzed arylation reaction of benzoxazoles with aryl bromides. 10 Hoover et al synthesized a series of arylated benzoxazoles via the CuI-catalyzed oxidative coupling reaction of 2-nitrobenzoic acids and benzoxazoles. 11 Maiti et al…”

Palladium‐Catalyzed Alkenylation of Azaarylmethylamines with Vinyl Halides

“…This result indicated NIXANTPHOS (L1) again showed enhanced reactivity over the structurally similar Xantphos (L2). [13][14][15][16][17] Regarding the palladium source, Pd(dba) 2 afforded higher AY (91% yield, entry 3) with NIXANTPHOS than Pd(OAc) 2 (78% yield, entry 1). [PdCl(allyl)] 2 and Pd(NCPh) 2 Cl 2 afforded good yields (80% and 79% respectively, entries 4 and 5), but lower than Pd(dba) 2. Our study of the palladium loading (Pd:NIXANT-PHOS 1:1.5) indicated that the yield increased to 95% (92% isolated yield, entry 6) at 5 mol% loading, but dropped to 45% at 2.5 mol% loading (entry 7).…”

Palladium-Catalyzed Benzylic Arylation of Pyridylmethyl Silyl Ethers: One-Pot Synthesis of Aryl(pyridyl)methanols

“…Given the success of deprotonative cross-coupling processes (DCCP) in the functionalization of a variety of weakly acidic sp 3 C–H bonds, 7 we envisioned application of this approach to the functionalization of substituted pyridines. 7q,u We recently reported the Pd(OAc) 2 /NIXANTPHOS-catalyzed DCCP of pyridylmethyl ethers to generate either arylated secondary ethers (Scheme 1A) or tertiary alcohols via tandem arylation/ [1,2]-Wittig rearrangement (Scheme 1B).…”

“…7q,u We recently reported the Pd(OAc) 2 /NIXANTPHOS-catalyzed DCCP of pyridylmethyl ethers to generate either arylated secondary ethers (Scheme 1A) or tertiary alcohols via tandem arylation/ [1,2]-Wittig rearrangement (Scheme 1B). 7u Secondary aryl-(pyridyl)methanols (Figure 1) are also highly desirable but not accessible via the chemistry in Scheme 1A or B.…”

“…Based on the general utility of the Pd(OAc) 2 /NIXANT-PHOS-based catalyst in a range of reactions, 7j–u we began by investigating the benzylic C–H arylation of 2-pyridylmethyl silyl ether 1a with bromobenzene 2a using Pd(OAc) 2 (1 mol %) and NIXANTPHOS (1.5 mol %, see Table 1 for structure). Several combinations of silyl amide bases MN(SiMe 3 ) 2 (M = Li, Na, K) and solvents [toluene, 1,4-dioxane, THF, 2-methyltetrahydrofuran (2-MeTHF), cyclopentyl methyl ether (CPME), and 1,2-dimethoxyethane (DME)] were evaluated to identify suitable reaction conditions (Table 1, entries 1–10).…”