The Expedient and Regioselective Metalation of Unprotected Biphenyl‐2‐, ‐3‐, and ‐4‐carboxylic Acids

Abstract

Keywords: ortho-Lithiation / Unprotected benzoic acids / Organolithium compounds / Schlosser-Lochmann superbase / 9H-Fluoren-9-oneUnprotected biphenyl-2-carboxylic acid can be cleanly metalated with sec-butyllithium at the position adjacent to the carboxylate and can then be subjected to site-selective electrophilic substitution. The remote C2Ј-position is attacked by the superbasic mixture of n-butyllithium and potassium tertbutoxide (LICKOR, 3.5 equiv.) in THF or benzene at 20-

9‐Fluorenylphosphines for the Pd‐Catalyzed Sonogashira, Suzuki, and Buchwald–Hartwig Coupling Reactions in Organic Solvents and Water

“…1-Methylfluorenone was prepared according to Mortier et al, [73] deprotonated and reacted with ethyliodide to result in 1-methyl-9-ethylfluorene. Another sequence of deprotonation and quenching with Cy 2 PCl gave the 9,9-disubstituted 1-methylfluorene, which was isolated as the respective phosphonium salt after protonation with HBF 4 (Scheme 2).…”

RuH2(CO)(PPh3)3-catalyzed arylation of aromatic esters using arylboronates via C–H bond cleavages

“…When ester 11a was treated with conc. HBr in AcOH [13] was performed in a sealed tube at 120°C for 65 h, hydrolysis took place cleanly, and 2,6-diphenylbenzoic acid (12) [14] was isolated in 93% yield (see Scheme 2).…”

“…IR (neat): 3060, , 1015 . MS m/z (% relative intensity): 241 (11), 240 (M + , 65), 196 (16), 195 (100), 194 (48), 167 (14), 166 (14), 165 (42) : d = 19.7, 21.4, 68.5, 127.1, 127.2, 128.1, 128.4, 129.0, 129.1, 133.6, 135.0, 139.9, 140.8, 169.0. IR (neat): 3060, 3027, 2979: d = 19.7, 21.4, 68.5, 127.1, 127.2, 128.1, 128.4, 129.0, 129.1, 133.6, 135.0, 139.9, 140.8, 169.0.…”

Carbanions and Electrophilic Aliphatic Substitution

“…59 Unprotected biphenyl-2-carboxylic acid has been cleanly metalated with sec-butyllithium at the position adjacent to the carboxylate and can then be subjected to site-selective electrophilic substitution (Scheme 8). The remote C(2 )-position has been attacked by the superbasic mixture of n-BuLi and t-BuOK (LICKOR) in THF or benzene.…”