Synthesis and NMR studies of 2- and 3-fluorosubstitued five-membered heterocycles

Fluoridation of 2‐thienyliodonium salts

“…2-Fluorothiophene also has limited UV activity making detection by TLC and HPLC difficult/inconsistent. Analysis of the radiofluoridation of 2-thienyl(phenyl) iodonium tosylate initially gave a single peak by radio HPLC however after extensive method development (following our concerns, in this case about co-elution) this was found to actually consist of two components}the first fluorobenzene was as expected, the second appeared to be 2-fluorothiophene (an authentic sample was prepared by lithiation of thiophene and a quench with NFSI 6 ). In summary the detection, characterization and isolation of 2-fluorothiophene is extremely problematic.…”

Substituent effects on indirect carbon–carbon couplings, J(CC), in substituted thiophenes, pyrroles, and furans studied by experiment and theory

“…Almost all of the experimental 2 J (CC)'s come from the present work; only three, those for compound 30 (Table ), have been taken from Nielsen et al . Among the 188 experimental 1 J (CC)'s, 108 are new and come from the present work; the other are taken from the literature, mostly from our previous work . For some compounds, the data have been re‐measured and marked as such in the tables.…”

“…Most of the compounds studied in the present work were either available commercially (Aldrich: 1 , 2 , 3 , 8 , 12 , 13 , 22 , 23 , 24 , 25 , 29 , 32 , 38 , 58 , 59 , 65 , 68 ) or were synthesized according to the published procedures: 4 , 5 , 6 , 7 , 9 , 10 , 11 , 14 , 15 , 16 , 17 , , 18 , 19 , 20 , 21 , 30 , 31 , 33 , 34 , 39 , 40 , 41 , 43 ,, 45 , 46 , 48 , 49 , 50 , 51 , 52 , 53 , 54 , 55 , 60 , 61 , 62 , 63 , 64 , 66 , 69 , 70 , 72 , and 73 . Some compounds have been obtained as gifts from our colleagues: Dr A. Dąbrowski, 26 , 27 , 28 and Dr A. Kwast, 35 , 36 , 37 .…”

Five‐Membered Heterocycles: Pyrrole and Related Systems

“…This lithiopyrrole will subsequently react readily with a wide variety of electrophiles [398], and may for example also be converted into the 2-alkyl-1-methylpyrroles 261 by treatment with trialkylboranes, followed by addition of iodine or NCS [399,400]. Quenching of 2-lithio-1-methyl-5-noctylpyrrole with N-fluorodibenzenesulfonamide has been used to prepare the labile 2-fluoro-1-methyl-5-n-octylpyrrole [401]. Transmetallation of 260 formed from 1-methylpyrrole and t-BuLi with MgBr 2 or ZnCl 2 gives the corresponding metallated pyrroles 262 and 263, which can subsequently participate in palladium-catalyzed cross-coupling reactions leading to 2-arylpyrroles, or to the 2-pyridylpyrrole 264 [402].…”