Lithiation of polychloropyrimidines and dichloropyridines

A convenient synthesis of [2,6‐14C]‐2‐chloroisonicotinic acid

“…Since [2,[6][7][8][9][10][11][12][13][14] C]-2,6-dichloropyridine ( % 2) can be prepared readily as described by McKendry, Muelder and Wass, 7,8 it appeared to us that it should be possible to prepare 14 C-labeled 2,6-dichloroisonicotinic acid (…”

On the synthesis of heterocyclic dendrons

“…Elemental analyses were performed on a Perkin-Elmer 2400 CHN microanalyzer. NMR spectra were recorded on a Varian Unity operating at 299.980 MHz for 1 H and 75.423 MHz for 13 C. Chemical shifts are expressed in parts per million (δ) relative to TMS as internal standard. The resonances of compounds were assigned by difference NOE and Hetcor experiments.…”

“…The starting material, 2,6-dichloro-4-methylpyridine, was prepared by alkylation (n-BuLi/MeI) of 2,6-dichloropyridine according to a literature procedure 13 (Scheme 3). This compound is able to form biscarbenes by deprotonation of its corresponding quaternary disalts.…”

Metal‐Bearing and Trifluoromethyl‐Substituted Pyrimidines: Generation and Functionalization

“…This remained the sole example of a pyrimidine deprotonation at the 2-position. Radinov et al [8] reported the selective 5-lithiation of 4,6-dichloropyrimidine and 2,4,6-trichloropyrimidine using lithium diisopropylamide (LIDA) or butyllithium as the base. According to Quéguiner et al, [9,10] both butyllithium and LITMP promote similarly the metalation of 4-chloro-2,6-dimethoxypyrimidine at the 5-position, again the only vacant site.…”

“…LITMP served as the base in all three cases. Concomitant deprotonation at the 5-and 6-position was found to occur with 2,4-dichloropyrimidine [8,13] and 4-chloro-2-(methylthio)pyrimidine [13] (Scheme 5). In the latter case, the 5-/6-ratio varied strongly depending on the base employed, approximating 20:1 with LIDA and 1:2 with LITMP.…”