915144-99-9Relevant academic research and scientific papers
Stepwise mechanism for the bromination of arenes by a hypervalent iodine reagent
Arrieta, Ana,Cossío, Fernando P.,Granados, Albert,Shafir, Alexandr,Vallribera, Adelina
, p. 2142 - 2150 (2020/03/11)
A mild, metal-free bromination method of arenes has been developed using the combination of bis(trifluoroacetoxy)iodobencene and trimethylsilyl bromide. In situ-formed dibromo(phenyl)-λ3-iodane (PhIBr2) is proposed as the reactive intermediate. This methodology using PIFA/TMSBr has been applied with success to a great number of substrates (25 examples). The treatment of mono-substituted activated arenes led to para-brominated products (2u-z) in excellent 83-96% yields. Density functional theory calculations indicate a stepwise mechanism involving a double bromine addition followed by a type II dyotropic reaction with concomitant re-aromatization of the six-membered ring.
Proton mobility in 2-substituted 1,3-dichlorobenzenes: "ortho" or "meta" metalation?
Schlosser, Manfred,Heiss, Christophe,Marzi, Elena,Scopelliti, Rosario
, p. 4398 - 4404 (2007/10/03)
Nine 1,3-dichlorobenzene congeners were selected as model compounds to assess the relative rates of proton abstraction from 4- and 5-positions ("ortho" vs. "meta" metalation). Using lithium 2,2,6,6-tetramethylpiperidide as the basic reagent, the chlorine-adjacent 4-position underwent metalation exclusively. In contrast, attack at the chlorine-remote 5-posi" tion became significant even in the case of moderately sized 2-substituents (such as dimethylamino or ethyl) when secbutyllithium was employed. The "ortho/para" (4-/5-) ratios ranged from 80:20 to 65:35. The more pronounced "meta-orienting" effect of silicon as opposed to carbon substituents can be attributed to dissimilarities in the n polarization of the aromatic ring. Wiley-VCH Verlag GmbH & Co. KGaA, 2006.
