The single fluorine atom of 2-fluoro-3-trifluoromethylfurans and -thiophenes can be readily replaced by various nucleophiles. Depending on the substituent pattern, certain products obtained upon nucleophilic substitution with benzyl alcohols are susceptible to [1,3]- and [1,5]-benzyl group migrations under very mild conditions. Therefore, these rearrangements can be integrated into domino reactions
Partially Fluorinated Heterocycles from 4,4-Bis(trifluoromethyl)-hetero-1,3-dienes via C–F Bond Activation – Synthesis of 2-Fluoro-3-(trifluoromethyl)furans
An efficient synthesis of 2-fluoro-3-(trifluoromethyl)furans was developed. Keystep of the reaction sequence is a [4 + 1] cycloaddition reaction of tin(II)chloride to 4,4-bis(trifluoromethyl)-1-oxabuta-1,3-dienes. At elevated temperatures the tin heterocycles are transformed into 1-aryl-4,4-difluoro-3-(trifluoromethyl)but-3-en-1-ones which on treatment with sodium hydride in dry DMF give 2-fluoro-3-(trifluoromethyl)furans. The single fluorine bound to C-(2) can be readily replaced by various N-, O-, S-, and C-nucleophiles and dinucleophiles.
Ein neues Verfahren zur positionsselektiven Einf�hrung von Trifluormethylgruppen in Heteroaromaten: Synthese von 3-Trifluormethylfuranen
作者:Klaus Burger、Brigitte Helmreich
DOI:10.1002/prac.19923340404
日期:——
Transformation of 4,4-bis(trifluoromethyl)-1-oxabuta-1,3-dienes (2) into 2-fluoro-3-trifluoromethylfurnas (4) can be achieved in a two step procedure by treatment with tin (II) chloride and sodium hydride. The fluorine atom at skeleton position 2 is replaced smoothly by various nucleophiles. The reaction sequence represents a preparatively simple method for the selective introduction of biologically relevant substituents into 3-trifluoromethylfurans.