72856-74-7Relevant academic research and scientific papers
First general, direct, and regioselective synthesis of substituted methoxybenzoic acids by ortho metalation
Nguyen, Thi-Huu,Chau, Nguyet Trang Thanh,Castanet, Anne-Sophie,Nguyen, Kim Phi Phung,Mortier, Jacques
, p. 3419 - 3429 (2008/02/03)
(Chemical Equation Presented) New general methodology of value in aromatic chemistry based on ortho-metalation sites in o-, m-, and p-anisic acids (1-3) (Scheme 1) is described. The metalation can be selectively directed to either of the ortho positions by varying the base, metalation temperature, and exposure times. Metalation of o-anisic acid (1) with s-BuLi/TMEDA in THF at -78°C occurs exclusively in the position adjacente to the carboxylate. On the other hand, a reversal of regioselectivity is observed with n-BuLi/t-BuOK. With LTMP at 0°C, the two directors of m-anisic acid (2) function in concert to direct introduction of the metal between them while n-BuLi/t-BuOK removes preferentially the proton located ortho to the methoxy and para to the carboxylate (H-4). s-BuLi/TMEDA reacts with p-anisic acid (3) exclusively in the vicinity of the carboxylate. According to these methodologies, routes to very simple methoxybenzoic acids with a variety of functionalities that are not easily accessible by other means have been developed (Table 1).
METALATION REACTIONS. VI. STERIC LIMITS IN THE PREPARATION OF 1,2,3-TRI-SUBSTITUTED BENZENE DERIVATIVES
Cabiddu, Salvatore,Maccioni, Antonio,Piras, Pier Paolo,Plumitallo, Antonio
, p. 123 - 128 (2007/10/02)
Metalation of 1,3-dialkoxy-, 1-alkoxy-3-(alkylthio)- and 1,3-bis-(alkylthio)-benzenes with n-butyllithium has been examined to verify the possibility of preparing 1,2,3-tri-substituted benzene derivatives.The reaction is affected by steric hindrance.The yields of the metalation in the position ortho to both the substituents decrease as steric requirement increases becoming zero when the bulk of both the alkyl substituent and the hetero-atom is increased.It has been shown that synthesis of 1,2,3-tri-substituted derivatives by this route is feasible only with small substituents.
