Regioselective Generation of Aryllithiums from Substituted Bromobenzenes XC₆H₄Br (X = 4‐Br, 4‐I, 4‐CN, 2‐CN)

Abstract

Selected activated bromobenzenes XC 6 H 4 Br (X = 4-Br, 4-I, 4-CN, 2-CN) were successfully deprotonated with lithium 2,2,6,6-tetramethylpiperidide (LTMP) in THF at -80°C. Thus, 2,5-dibromo-, 2-bromo-5-iodo-, 5-bromo-2-cyano-, and 3-bromo-2-cyanophenyllithium were obtained as stable intermediates and could be converted by subsequent reactions

Copper‐Promoted Tandem Three‐Component Access to Quinazolin‐4(H)‐imines and Benzimidazo[1,2‐c]quinazolines

“…The reaction was however not limited to commercially available 2‐cyanophenylboronic acid (Scheme ). Indeed, use of 2‐cyano‐4‐bromophenylboronic acid ( 1 b ) delivered chemoselectively the 7‐bromo‐analogue 5 p in good yield, thereby demonstrating the tolerance to a bromine substituent under these metal catalyzed conditions. 6,7‐Dimethoxy‐analogue 5 r could also be produce uneventfully, starting from (2‐cyano‐4,5‐dimethoxyphenyl)boronic acid ( 1 c ) .…”

Enantioselective Diels–Alder Reaction Induced by Chiral Supramolecular Lewis Acid Catalysts Based on CN···B and PO···B Coordination Bonds

“…The titled compound was prepared from 4-(trifluoromethyl)benzonitrile according to the reported procedure. 6 1 H NMR (400 MHz, CD 3 OD) δ 7.84 (d, J = 8.0 Hz, 1H), 7.93 (d, J = 7.8 Hz, 1H), 8.00 (s, 1H). 13 C NMR (100 MHz, CD 3 OD) δ 119.3, 120.5, 125.0 (q, J C-F = 270 Hz), 125.3, 127.6 (q, J C-F = 2.9 Hz), 131.4, 134.2 (q, J C-F = 32.4 Hz), 134.…”

Long-range Effect of Bromine in the Deprotonative Metalation of Aromatic Compounds

“…[10] 1-Bromo-2-fluorobenzene (4a) and 1-bromo-4-fluorobenzene (5a) can be functionalized next to fluorine upon consecutive treatment with LiDA (DA = diisopropylamino) in THF at -75°C and dry . [18] After interception with carbon dioxide and acidification, the functionalized derivative 8b is isolated in 84% yield; using the slightly weaker base LiDA instead of LiTMP affords the same benzoic acid in 68% yield. Iodine proves to exhibit a similar long-range acidifying/stabilizing effect, as shown in Scheme 4.…”

“…Iodine proves to exhibit a similar long-range acidifying/stabilizing effect, as shown in Scheme 4. [18] Provided that the reaction temperature with LiDA is maintained at -85°C, extension of the reaction to 2,5-dibromoanisole is possible, giving 2,5-dibromo-3-methoxybenzaldehyde in a moderate 47% yield after DMF quench and hydrolysis. [19] Similarly, 2-and 4-bromobenzonitrile (10a and 11a) benefit from the long-range meta-acidifying effect of bromine.…”

“…Such a result can be evidenced by subsequent derivatization to the corresponding boronic acids 10b and 11b by trapping with trimethylborate followed by hydrolysis (Scheme 5). [18] benzene fails to yield 2-bromobenzoic acid due to degradation whatever the conditions used. [9,15] This result shows that chlorine and bromine, even when located at a position meta to the deprotonation site, exhibit a stabilizing effect.…”