- Theoretical and experimental study on the reactivity of methyl dichlorobenzoates with sulfur-centered nucleophiles by electron transfer reactions
-
Reactions of methyl 2,5-dichlorobenzoate or methyl 3,6-dichloro-2- methoxybenzoate with sulfur-centered nucleophiles gave mono- and disubstitution products, respectively through SRN1 mechanism in liquid ammonia. Products obtained could be potential herbicides less toxic to the environment. Theoretical studies explained the reactivity observed considering geometries, and spin densities of radical anions and potential energy surfaces for the dissociation of the radical anions formed.
- Uranga, Jorge G.,Monta?ez, Juan P.,Santiago, Ana N.
-
experimental part
p. 584 - 589
(2012/02/05)
-
- First general, direct, and regioselective synthesis of substituted methoxybenzoic acids by ortho metalation
-
(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).
- Nguyen, Thi-Huu,Chau, Nguyet Trang Thanh,Castanet, Anne-Sophie,Nguyen, Kim Phi Phung,Mortier, Jacques
-
p. 3419 - 3429
(2008/02/03)
-
- Directed ortho-metalation of unprotected benzoic acids. Methodology and regioselective synthesis of useful contiguously 3- and 6-substituted 2-methoxybenzoic acid building blocks
-
By treatment with s-BuLi/TMEDA at -78 °C, unprotected 2-methoxybenzoic acid is deprotonated exclusively in the position ortho to the carboxylate. A reversal of regioselectivity is observed when the acid is treated with n-BuLi/t-BuOK. These results are of general utility for the one-pot preparation of a variety of very simple 3- and 6-substituted 2-methoxybenzoic acids that are not easily accessible by conventional means. The potential usefulness of the method is demonstrated by the expedient synthesis of lunularic acid.
- Nguyen, Thi-Huu,Castanet, Anne-Sophie,Mortier, Jacques
-
p. 765 - 768
(2007/10/03)
-
- Accelerating effect of meta substituents in the ester-mediated nucleophilic aromatic substitution reaction
-
The ester-mediated nucleophilic aromatic substitution (SNAr) reaction of 2-methoxybenzoic ester 1 with Grignard reagents 11 is greatly accelerated by introduction of a methoxy or halo substituent at the 3-position of the benzoate ring (7-10). The substituent effects of these groups at the 3-position are compared with those at the 5-position to suggest that the activation mechanism of the methoxy substituent is different from that of the halo substituent; the ligating ability of the 3-methoxy group plays a crucial role in enhancing the reactivity of the 2-methoxy moiety, while the electron-withdrawing ability is more important in the case of the halo groups. It has also been found that introduction of an additional methoxy substituent at the meta-position (33, 34) enables the SNAr methoxy-displacement reaction even at the para-position to the ester activator. The accelerating effect of the 3-bromo substituent is advantageously utilized for regioselective allylation of 3-bromo-2,6-dimethoxybenzoic ester 55 at the 2-position to provide an easy access to a multisubstituted naphthol 59, which is a key compound for the syntheses of michellamines A-C and the related naphthylisoquinoline alkaloids.
- Hattori, Tetsutaro,Takeda, Ayanobu,Suzuki, Kenji,Koike, Nobuyuki,Koshiishi, Eiji,Miyano, Sotaro
-
p. 3661 - 3671
(2007/10/03)
-