New syntheses of 2-fluoroisovanillin and 5-fluorovanillin

Abstract

someric option available to the zwitterions 10-13 depicted in Scheme III, that are related to 3, 5,6, and 7, respectively.Consideration of the stability of such zwitterions, i.e., 10 >11 and 13 > 12, readily leads to prediction of regioselectivity. However, prediction of the correct regioisomers 10 or 13 cannot easily be achieved on this basis. Experimental SectionThe radical anion of 2 was measured on a Varían 4502-10A; X band. The electrolysis was performed with a 10"4 M solution of 2 in dimethylformamide with tetra-n-butylammonium iodide as a supporting electrolyte, 10 µ at -1.45 V. The cell used in these experiments was deoxygenated in a glovebox.

Antineoplastic Agents. 509. Synthesis of Fluorcombstatin Phosphate and Related 3-Halostilbenes,1

“…Preparation of the stilbenes was accomplished as shown in Scheme and Figure . Phosphonium bromide 7 was prepared as previously described,9c and condensation with the appropriate halobenzaldehyde − using n -butyllithium in THF led to silyl-protected stilbenes 8 − 10 . Subsequent deprotection (Scheme ) with tetrabutylammonium fluoride afforded 3-halostilbenes 11 − 13 .…”

“…3-Fluoro-4,5-dimethoxybenzaldehyde (4). To a stirred solution prepared from 100 mL of DMF and 5-fluorovanillin (lit . 1.0 g, 5.88 mmol) was added portionwise over 15 min sodium hydride (60% in mineral oil, 282 mg, 7 mmol).…”

“…To a stirred solution prepared from 100 mL of DMF and 5-fluorovanillin (lit. 10 1.0 g, 5.88 mmol) was added portionwise over 15 min sodium hydride (60% in mineral oil, 282 mg, 7 mmol). After 15 min, iodomethane (1.5 mL, 24 mmol) was added, and stirring continued for 16 h at RT.…”

Chemoselective Zinc/HCl Reduction of Halogenated β-Nitrostyrenes: Synthesis of Halogenated Dopamine Analogues

“…5 m-Fluoroanisole was easily converted into 5-fluorovanillin (2b) following a known procedure. 6 However, we found that the equivalent preparation of 2fluoroisovanillin (2a) 6 in fact yields an inseparable 1:1 mixture of regioisomers with a melting point identical to the reported melting point of supposedly pure 2-fluoroisovanillin. 7 As a result, we found it more economical to prepare 2-fluorodopamine (1a) via an alternative scheme.…”

Cytotoxic and antivascular 1-methyl-4-(3-fluoro-4-methoxyphenyl)-5-(halophenyl)-imidazoles

“…3-Fluoro-4-methoxybenzaldehyde 4 was reacted with p-toluenesulfinic acid and formamide in the presence of camphorsulfonic acid (CSA) to give a tosylmethylformamide intermediate, which was dehydrated to 5 by POCl 3 . The halogenated benzaldehydes used for the van Leusen reaction with 5 were prepared according to known literature methods 12,15,20 and converted to their N-methylimines. Reaction of the latter with 5 and addition of HCl/dioxane finally afforded the imidazolium salts 6 (Scheme 1).…”