- Method for estimating SN1 rate constants: Solvolytic reactivity of benzoates
-
Nucleofugalities of pentafluorobenzoate (PFB) and 2,4,6-trifluorobenzoate (TFB) leaving groups have been derived from the solvolysis rate constants of X,Y-substituted benzhydryl PFBs and TFBs measured in a series of aqueous solvents, by applying the LFER equation: log k = sf(Ef + Nf). The heterolysis rate constants of dianisylmethyl PFB and TFB, and those determined for 10 more dianisylmethyl benzoates in aqueous ethanol, constitute a set of reference benzoates whose experimental ΔG ? have been correlated with the ΔH? (calculated by PCM quantum-chemical method) of the model epoxy ring formation. Because of the excellent correlation (r = 0.997), the method for calculating the nucleofugalities of substituted benzoate LGs have been established, ultimately providing a method for determination of the SN1 reactivity for any benzoate in a given solvent. Using the ΔG? vs ΔH? correlation, and taking sf based on similarity, the nucleofugality parameters for about 70 benzoates have been determined in 90%, 80%, and 70% aqueous ethanol. The calculated intrinsic barriers for substituted benzoate leaving groups show that substrates producing more stabilized LGs proceed over lower intrinsic barriers. Substituents on the phenyl ring affect the solvolysis rate of benzhydryl benzoates by both field and inductive effects.
- Matic, Mirela,Denegri, Bernard,Kronja, Olga
-
supporting information
p. 8986 - 8998,13
(2012/12/12)
-
- Divergent Pathways in the Reaction of Hexamethylbenzene with Dimethyldioxirane
-
Hexamethylbenzene (1) reacts with dimethyldioxirane (2) via three separate reaction pathways. In the major pathway the reaction proceeds through an arene oxide which is rapidly transformed to the oxepin valence tautomer. In the first example of the reaction of an oxepin with 2 the oxepin is oxidized to first the cis-dioxide and then to the trioxide with the third oxide trans to the other two oxide rings. In a second competing pathway a methyl group migrates in the first produced arene oxide to give a hexamethyl-cyclohexadienone. This material then reacts rapidly with 2 to give a trans-diepoxide. The third reaction pathway involves the C-H insertion reaction of 2. This process gives first the derived benzyl alcohol and then the corresponding benzoic acid. Two other minor products are also formed, one is rationalized as arising from reaction of the arene oxide with water. The other is a tricyclic compound of unknown origin.
- Murray, Robert W.,Singh, Megh,Rath, Nigam
-
p. 8794 - 8799
(2007/10/03)
-
- ELECTRON TRANSFER ACTIVATION. HYDROPEROXIDE INTERMEDIATES IN A NOVEL AND SELECTIVE PROCEDURE FOR BENZYLIC OXIDATIONS.
-
A selective and mild photochemical procedure for benzylic oxidations with 9,10-dicyanoanthracene (DCA) an usual electron acceptor, in the presence of methyl viologen (MV2+), an electron relay, has been developed.Methyl and methylene groups are oxidized in good to excellent yields to the corresponding hydroperoxides.
- Santamaria, J.,Jroundi, R.,Rigaudy, J.
-
p. 4677 - 4680
(2007/10/02)
-
- Oxidative Coupling of 1-(2,6-Dichlorobenzoyl)pyrroles and -pyrazoles and Alkyl Acrylates by Palladium(II) Acetate
-
Treatments of 1-(2,6-dichlorobenzoyl)-, 3-acetyl-1-(2,6-dichlorobenzoyl)-, 1-(2,6-dichlorobenzoyl)-2-formyl-, and 1-(phenylsulfonyl)pyrroles with palladium acetate and alkyl acrylates gave the corresponding α-alkenyl-substituted pyrroles in good yields, while the reaction of 1-(2,6-dichlorobenzoyl)-2,5-dimethylpyrrole gave small amounts of β-alkenyl-substituted pyrroles.Under similar conditions, 1-(2,6-dichlorobenzoyl)pyrazole and 1-(2,6-dichlorobenzoyl)-3,5-dimethylpyrazole reacted with palladium acetate and alkyl acrylates to give the corresponding 4-alkenyl-substituted pyrazoles.The reaction of 1-(2,6-dichlorobenzoyl)-4-methylpyrazole gave 5-alkenyl-substituted pyrazole.
- Itahara, Toshio,Kawasaki, Kazukuni,Ouseto, Fumio
-
p. 3488 - 3493
(2007/10/02)
-
- Process for preparing a methyl-substituted benzaldehyde
-
Process for formylating an alkyl-substituted benzene using carbon monoxide and hydrogen chloride, in the presence of aluminum chloride catalyst, in a reaction mixture which includes chlorobenzene as a solvent, and process for oxidizing an alkyl-substituted benzaldehyde using oxygen, in the presence of an autoxidation initiator, in a reaction mixture which includes cyclohexanone as a reductant.
- -
-
-