1,2-Didehydro-3- and -4-(trifluoromethoxy)benzene: the "aryne" route to 1- and 2-(trifluoromethoxy)naphthalenes
Upon treatment of 1-bromo-2-(trifluoromethoxy)benzene with lithium diisopropylamide (LDA) at -100 DegC, 3-bromo-2-(trifluoromethoxy)phenyllithium is generated. It can be trapped as such, but isomerizes to afford 2-bromo-6-(trifluoromethoxy)phenyllithium when the temp. is raised to -75 DegC. The latter intermediate can be directly obtained from 1-bromo-3-(trifluoromethoxy)benzene. 1-Bromo-4-(trifluoromethoxy)benzene gives 5-bromo-2-(trifluoromethoxy)phenyllithium at -100 DegC, but at -75 DegC it slowly eliminates lithium bromide, thus setting free 1,2-dehydro-4-(trifluoromethoxy)benzene. In the same way, 1,2-dehydro-3-(trifluoromethoxy)benzene can be generated from 1-bromo-3-(trifluoromethoxy)benzene. Both arynes can be intercepted in situ with furan. The resulting [4+2] cycloadducts can be reduced with zinc powder, giving 1- and 2-(trifluoromethoxy)naphthalenes, they may be submitted to acid-catalyzed isomerization to produce trifluoromethoxy-1-naphthols, or they may be brominated to afford vic-dibromo derivs. Base-promoted dehydrobromination of the latter compds. produces 2- or 3-bromo-1,4-epoxy-1,4-dihydro-5- or -6-(trifluoromethoxy)naphthalenes, which undergo regioselective ring-opening in acidic media and halogen/metal exchange when treated with butyllithium. [on SciFinder (R)]
2001
21
3991
3997
CAN 136:232103 25-24 Benzene, Its Derivatives, and Condensed Benzenoid Compounds Institut de Chimie organique de l'Universite,Lausanne-Dorigny,Switz. Journal 1434-193X written in English. 110-00-9 (Furan); 407-14-7 (1-Bromo-4-trifluoromethoxybenzene); 461-82-5 (4-Trifluoromethoxyaniline); 2252-44-0 (1-Bromo-3-trifluoromethoxybenzene); 64115-88-4 (1-Bromo-2-trifluoromethoxybenzene) Role: RCT (Reactant), RACT (Reactant or reagent) (prepn. of 1,2-didehydro-3- or -4-(trifluoromethoxy)benzene and its conversion to trifluoromethoxynaphthalenes); 83265-56-9P; 212696-37-2P; 220107-35-7P; 403646-49-1P; 403646-51-5P; 403646-67-3P; 403646-69-5P; 403646-71-9P; 403646-72-0P; 403646-73-1P; 403646-74-2P; 403646-75-3P; 403646-78-6P; 403646-83-3P; 403646-86-6P; 403646-87-7P; 403646-88-8P; 403646-89-9P; 403646-90-2P Role: RCT (Reactant), SPN (Synthetic preparation), PREP (Preparation), RACT (Reactant or reagent) (prepn. of 1,2-didehydro-3- or -4-(trifluoromethoxy)benzene and its conversion to trifluoromethoxynaphthalenes); 403646-45-7P (3-Bromo-2-(trifluoromethoxy)benzoic acid); 403646-46-8P (2-Bromo-6-(trifluoromethoxy)benzoic acid); 403646-47-9P (5-Bromo-2-(trifluoromethoxy)benzoic acid); 403646-48-0P (2-Bromo-5-(trifluoromethoxy)benzoic acid); 403646-52-6P; 403646-54-8P; 403646-56-0P; 403646-58-2P; 403646-63-9P; 403646-65-1P; 403646-76-4P; 403646-77-5P; 403646-79-7P; 403646-80-0P; 403646-81-1P; 403646-82-2P; 403646-84-4P; 403646-85-5P Role: SPN (Synthetic preparation), PREP (Preparation) (prepn. of 1,2-didehydro-3- or -4-(trifluoromethoxy)benzene and its conversion to trifluoromethoxynaphthalenes)
REVIEWED
EPFL