Deuterium Exchange between Arenes and Deuterated Solvents in the Absence of a Transition Metal: Synthesis of D‐Labeled Fluoroarenes

Abstract

Fluoroarenes can be selectively deuterated by H/D exchange with common deuterated solvents in the presence of a catalytic amount of an alkali metal carbonate or, for the less acidic arenes, stoichiometric quantities of potassium phosphate. This is a sustainable method that does not need transition metal catalysis or the multistep synthesis of a main‐group organometallics. This exchange needs to be taken into account when using H/D scrambling as a mechanistic probe in reactions involving fluoroarenes.

Non‐Chelate‐Assisted Palladium‐Catalyzed Aerobic Oxidative Heck Reaction of Fluorobenzenes and Other Arenes: When Does the C−H Activation Need Help?

“…The alkenylation of 1,2‐difluorobenzene or fluorobenzene is inefficient even when using a large excess of arene, and it reaches good yields only in the presence of the ligand bipy‐6‐OH. The observed reactivity for the fluoroarenes fits the acidity trend of the C−H bond that is cleaved, [54] which in turn parallels the ease of C−H activation also favored by the stronger Pd−C bond for fluoroaryls with ortho fluorines [55] . As the F‐substitution decreases the C−H activation becomes turnover limiting and eventually needs the assistance of bipy‐6‐OH.…”

“…This conversion is easy in the presence of base and does not require metal catalysis as has been reported before [54] . In this case just the presence of a catalytic amount of sodium molybdate in the presence of traces of H 2 O is enough for the conversion, as we tested independently (see SI).…”

“…[Pd(OAc) 2 ], N‐acetylglycine, 2,2'‐bipyridine, 1,10‐phenanthroline, 6‐methyl‐2(1 H )‐pyridinone, the arenes and the alkenes used are commercially available and were used as received unless otherwise indicated. [Pd(bipy‐6‐OH)Br(C 6 F 5 ) ( 18 ), [38] (NBu 4 )[Pd(bipy‐6‐O)Br(C 6 F 5 )] ( 21 ), [38] [PdBr(CH 3 CN) 2 (C 6 F 5 )], [60] (NBu 4 ) 2 [Pd 2 (μ‐Br) 2 Br 2 (C 6 F 5 ) 2 ], [61] [2,2′‐bipyridin]‐6(1 H )‐one (bipy‐6‐OH), [62] 1,10‐phenanthrolin‐2(1 H )‐one (phen‐2‐OH), [63] 1,10‐phenanthrolin‐4(1 H )‐one (phen‐4‐OH), [64] [2,2'‐bipyridin]‐4(1 H )‐one (bipy‐4‐OH), [65,66] 6‐methoxy‐2,2'‐bipyridine (bipy‐6‐OMe), [62] and C 6 F 5 D, [54] were prepared according to the procedures in the literature.…”

Three‐Component Synthesis of 2‐Substituted Thiobenzoazoles Using Tetramethyl Thiuram Monosulfide (TMTM) as Thiocarbonyl Surrogate

“…However, the control experiments without any catalyst (entry 14) showed that catalyst was not crucial in this reaction. To our delight, the reaction would be significantly promoted when a series of bases were added (entries [15][16][17][18][19][20][21][22][23], and the screening of bases showed that Na 2 CO 3 was the best. Thus, the optimal reaction conditions were summarized in entry 15, Table 1.…”

“…In recent years, owing to the pursuit of economy and ecofriendliness, alkali-catalyzed reactions, especially alkali metal carbonates, have become more and more popular. [16] Shen and co-workers [17] developed a highly selective functionalized C(sp 3 )-F bond formation strategy by efficient combination of TBAB (tetra-n-butylammonium bromide) and Cs 2 CO 3 . Shi [18] disclosed the cascade dimerization and cyclization of 2-sulfoaminoacrylate derivatives catalyzed by the inorganic base K 2 CO 3 to synthesize dihydro-2-oxopyrrole (DPO) derivatives in one step.…”