Fluorine- and trifluoromethyl-substituted toluenes: site selective metalation of aromatic or benzylic positions

At -75 Deg, the superbasic mixt. of BuLi and KOCMe3 metalates 2-, 3-, and 4-FC6H4Me exclusively at an arom. position adjacent to the halogen, as demonstrated by quenching with CO2 to give the corresponding benzoic acids. In contrast, a mixt. of LiN(CHMe2)2 and KOCMe3 selectively deprotonates the benzylic positions of 2- and 3-FC6H4Me to give after quenching with CO2 the corresponding phenylacetic acids. With 3-(F3C)C6H4Me, metal/hydrogen exchange again occurs at the Me group while the corresponding 2- and 4-isomers do not produce interceptable organometallic intermediates. [on SciFinder (R)]


Published in:
Synlett, 2, 119-21
Year:
1991
Keywords:
Note:
CAN 114:206686
25-17
Benzene, Its Derivatives, and Condensed Benzenoid Compounds
Inst. Chim. Org.,Univ. Lausanne,Lausanne,Switz.
Journal
0936-5214
written in English.
133620-74-3P Role: PREP (Preparation) (formation and polymn. of); 315-31-1P (2-Fluoro-3-methylbenzoic acid); 321-12-0P (2-Fluoro-5-methylbenzoic acid); 331-25-9P; 351-35-9P; 405-50-5P; 451-82-1P (2-Fluorophenylacetic acid); 7697-23-6P (2-Fluoro-4-methylbenzoic acid); 133620-73-2P Role: SPN (Synthetic preparation), PREP (Preparation) (prepn. of); 865-47-4 Role: RCT (Reactant), RACT (Reactant or reagent) (reagent from butyllithium or lithium diisopropylamide and, for regioselective metalation of fluoromethylarenes); 109-72-8 (Butyllithium) Role: USES (Uses) (reagent from potassium butoxide and, for regioselective metalation of fluoromethylarenes); 4111-54-0 (Lithium diisopropylamide) Role: RCT (Reactant), RACT (Reactant or reagent) (reagent from potassium butoxide and, for regioselective metalation of fluoromethylarenes); 95-52-3 (2-Fluorotoluene); 352-32-9 (4-Fluorotoluene); 352-70-5; 401-79-6 (3-(Trifluoromethyltoluene) Role: RCT (Reactant), RACT (Reactant or reagent) (regioselective metalation of, with potassium butoxide-butyllithium or -lithium diisopropylamide)
Laboratories:




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