Ortho-lithiation. A regiospecific route to ortho-substituted aryl ketones

Studies in organic mass spectrometry. Part 25. Benzyl ion formation in chemical ionisation (methane or isobutane) of someortho-alkylhetero-substituted diphenylcarbinols

“…This compound was synthesised by Grignard reaction between 2‐thiomethylacetophenone10 (6mmol) and phenylmagnesium bromide (Aldrich) (12 mmol) in anhydrous diethyl ether. Pure 5 was obtained as pale yellow oil (70%) by column chromatography on silica gel using cyclohexane/diethyl ether (9:1) as eluent.…”

Pyridine Elaboration Through Organometallic Intermediates: Regiochemical Control and Completeness

“…As first demonstrated by H.W. Gschwend et al, [40] the lithium -dialkylaminomethoxide unit provides neighboring group assistance to the metalation of adjacent aromatic positions. In the intramolecular competition with a methoxy group, the chelating N-(2-dimethylaminoethyl)-Nmethylamino chain proves to be a superior and the less flexible N'-methyl-N-piperidazyl ring an inferior ortho-directing substituent.…”

Simple and Clean Photo-induced Methylation of Heteroarenes with MeOH

“…23 In this regard, radical addition onto the heteroarenes could be a promising strategy to complement these transition-metal-catalyzed protocols for the methylation of heteroarenes. Since the pioneering work of Minisci et al, 24,25 many methods have been developed to methylate electron-deficient heteroarenes (10) via the addition of methyl radicals from different precursors such as acetic acid, 26 DMSO, 27,28 tert-butyl hydroperoxide (TBHP), 29 and others 30,31 to generate the methylated heteroarenes (11). However, these classic Minisci protocols require transition metals such as Ag or Fe and strong oxidants, and they usually require increased temperatures, which could complicate the purification and narrow the substrate scope.…”

“…The classic tool for methylation of aromatics is via directed ortho-metalation, [10][11][12] which entails a stoichiometric amount of strong base such as n-BuLi and the presence of heteroatoms as directing groups. In the past decade, another breakthrough in the field of methylation has been C-H activation.…”