An Improved Method for the Bromination of Metalated Haloarenes via Lithium, Zinc Transmetalation:  A Convenient Synthesis of 1,2-Dibromoarenes

Abstract

A facile protocol for the synthesis of 1,2-dibromoarenes is described. A standard ortho-lithiation/bromination procedure, when applied to bromoarenes, resulted in poor yields of the corresponding 1,2-dibromoarenes (13-62% yield). However, transmetalation of the transient aryllithium intermediate to an arylzinc species with ZnCl2, followed by bromination, resulted in dramatically improved yields of the synthetically useful 1,2-dibromoarenes (68-95% yield).

Coordination chemistry of perhalogenated cyclopentadienes and alkynes. XXVIII new high-yield synthesis of monobromoferrocene and simplified procedure for the synthesis of pentabromoferrocene. Molecular structures of 1,2,3-tribromoferrocene and 1,2,3,4,5-pentabromoferrocene

“…NMR analysis showed no traces of unreacted ferrocene or higher brominated ferrocenes. (Scheme 2) For the preparation of 1,2-dibromoferrocene (2) we used a recent synthetic protocol for 1,2-dibromoarenes via a lithium-zinc transmetallation, published by Menzel et al [11]. 1 was selectively orthometalated with LiTMP followed by lithium-zinc-exchange (5) g ¼ 90.000 (5 via ZnCl 2 and then the intermediate aryl zinc species was carefully brominated with elemental bromine.…”

Hole Transfer from Photoexcited Quantum Dots: The Relationship between Driving Force and Rate

“…This strategy allowed for controlled successive ortho-additions of bromine (Supporting Information, Figure S1). 47,48 Br 3 Fc was synthesized from Br 2 Fc with a high enough yield that a simple column and recrystallization resulted in pure Br 3 Fc. However, bromination of BrFc to make Br 2 Fc had a much lower yield, resulting in a 60:40 ratio of Br 2 Fc to BrFc.…”

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

“…As expected, 3-bromobenzonitrile lithiates at C-2 with LTMP owing to a cooperating acidifying effect of two adjacent substituents to give an intermediate stable at -75°C. [15] We found previously that the in situ metalation/disilylation of 4-bromobenzonitrile (3) with LDA/TMSCl gives 2,5-bis-(trimethylsilyl)-4-bromobenzonitrile, which might reflect comparable ortho-directing ability of bromine with respect to the CN group. [13] Similarly, the in situ lithiation/disilylation of 2-bromobenzonitrile (4) is also very effective and provides 3,6-bis(trimethylsilyl)-2-bromobenzonitrile with a high yield.…”