Microwave-assisted Synthesis of Diaryl Ethers from Reactions of Phenols with Nitroaryl Fluorides under Solvent-free Conditions

P(i-BuNCH2CH2)3N: An Efficient Promoter for the Nucleophilic Aromatic Substitution Reaction of Aryl Fluorides with Aryl TBDMS (or TMS) Ethers

“…The yield obtained in the traditional S N Ar reaction of 4-fluoronitrobenzene with 4-cyanophenol using KOH/DMSO/55 °C was significantly higher (98% isolated yield) compared with ours (73% isolated yield, entry 7 in Table ). On the other hand, the isolated yield (93%) we obtained for the reaction detailed in entry 8 demonstrates the somewhat greater efficacy of the proazaphosphatrane catalyst 3 than the similar reaction performed with 4-methoxyphenol in the presence of KF−Al 2 O 3 /Aliquat 336 (MeOct 3 N + Cl - ) in a microwave oven (92%).…”

“…It is worth noting that the conventional S N Ar reactions of 4-fluorobenzonitrile and 4-fluoronitrobenzene with 2- tert -butylphenol, promoted by KF−Al 2 O 3 /18-crown-6, required 120 and 84 h, respectively, to proceed to completion in refluxing CH 3 CN, and the corresponding coupling products were obtained in 83 and 98% yields, respectively 3d. However, under more forcing conditions (KF−Al 2 O 3 /Aliquat 336, microwave, no solvent), the S N Ar coupling of 4-fluoronitrobenzene with 2- tert -butylphenol provided the diaryl ether product in 90% yield in 10 min …”