Partially Fluorinated Heterocycles from 4,4-Bis(trifluoromethyl)-hetero-1,3-dienes via C–F Bond Activation – Synthesis of 2-Fluoro-3-(trifluoromethyl)furans
摘要:
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.
Synthese von 4,4-Bis(trifluormethyl)-1-oxabuta-1,3-dienen
摘要:
Silyl enol ethers (1) and hexafluoroacetone (2) react to give O-silylated aldol adducts 3 which, after desilylation with methanol/hydrochloric acid, are transformed into 4.4-bis(trifluoromethyl)-1-oxabuta-1,3-dienes (5) on treatment with trifluoroacetic acid anhydride/pyridine.
Synthesis of 3-trifluoromethylfurans from β,β-bis(trifluoromethyl)α,β-unsaturated ketones and tin(<scp>II</scp>) chloride
作者:Klaus Burger、Brigitte Helmreich
DOI:10.1039/c39920000348
日期:——
A new building block strategy for the synthesis of 3-trifluoromethyl-substituted furans 9 and 10 is described from β,β-bis(trifluoromethyl)α,β-unsaturated ketones 2via reductive fluoride elimination and 1,5-electrocyclization with elimination.
A one-pot procedure for the synthesis of 2-fluoro-3-trifluoromethyl- substituted thiophens 6 from 1-aryl-4,4-difluoro-3- trifluoromethylbut-3-en-1-one (3) and phosphorus pentasulfide is described. The fluorine atom at C-2 of compounds 6 undergoes nucleophilicdisplacement reactions.
Synthesis of 2-Fluoro-3-trifluoromethylthiophenes and 3-Trifluoromethylthiophenes from Hexafluoroacetone
作者:Klaus Burger、Brigitte Helmreich、Vera Ya. Popkova、Lev S. German
DOI:10.3987/com-94-s(b)82
日期:——
The transformation of bis(trifluoromethyl)-1-oxabuta-1,3-dienes (1) - available from hexafluoroacetone - into 2-fluoro-3-trifluoromethylthiopheneses (9) via 4,4-difluoro-3-trifluoromethyl-3-buten-1-ones (5) is described. The fluorine atom at skeleton position 2 of the thiophenes (9) is readily displaced by various nucleophiles.
Burger Klaus, Helmreich Brigitte, Popkova Vera Ya., German Lev S., Heterocycles, 39 (1994) N 2, S 819-832
作者:Burger Klaus, Helmreich Brigitte, Popkova Vera Ya., German Lev S.
DOI:——
日期:——
Synthese von 4,4-Bis(trifluormethyl)-1-oxabuta-1,3-dienen
作者:Klaus Burger、Brigitte Helmreich
DOI:10.1002/prac.19923340304
日期:——
Silyl enol ethers (1) and hexafluoroacetone (2) react to give O-silylated aldol adducts 3 which, after desilylation with methanol/hydrochloric acid, are transformed into 4.4-bis(trifluoromethyl)-1-oxabuta-1,3-dienes (5) on treatment with trifluoroacetic acid anhydride/pyridine.