940934-42-9Relevant academic research and scientific papers
Effect of the leaving group solvation on solvolytic behavior of benzhydryl derivatives
Denegri, Bernard,Kronjaa, Olga
experimental part, p. 495 - 503 (2010/04/30)
An effect of the leaving group (LG) solvation on reactivity of benzhydryl derivatives in SN1 reactions has been investigated by using X, Y-substituted benzhydryl phenyl carbonates, methyl carbonates, 3, 5-dinitrobenzoates (DNB), and the corresponding benzhydryl chlorides as reference compounds. Reaction constants (sf) derived from LFER equation log k (25°C)=sf (Nf+Ef) indicate that s f parameters of carbonates and DNBs decrease as the fraction of the water in a given solvent/water mixture increases, while those of chlorides remain unchanged. This phenomenon is due to less important solvation and less charge separation in the TS. Effects of the solvents on the reaction rates were analyzed by Grunwald-Winstein correlations using various solvent-ionizing power scales. The m values obtained for carbonates and DNBs are considerably smaller than the m values for chlorides. Also, the solvolysis rate constants of substrates that have stronger electrofuges are less influenced by solvent (lower m) than those with weaker electrofuges. Values of m parameters obtained for a given substrate in a given binary solvent system correlate well with the electrofugality of the generated benzhydrylium ion. Abscissa at which m=0 represents the extrapolated critical electrofugality Ecrit f of the substrates whose solvolysis rates should not depend on the water fraction in the aqueous/organic solvent mixtures. Similar values for the critical electrofugality have also been obtained from extrapolated logk versus Ef plots. Copyright
Nucleofugality of phenyl and methyl carbonates
Denegri, Bernard,Kronja, Olga
, p. 8427 - 8433 (2008/03/12)
(Chemical Equation Presented) A series of X,Y-substituted benzhydryl phenyl carbonates 1 and X,Y-substituted benzhydryl methyl carbonates 2 were subjected to solvolysis in different methanol/water, ethanol/water, and acetone/water mixtures at 25°C. The LFER equation, log k = sf(Ef + Nf), was used to derive the nucleofuge-specific parameters (N f and sf) for phenyl carbonate (1LG) and methyl carbonate (2LG) leaving groups in a given solvent in SN1 type reaction. Kinetic measurements showed that phenyl carbonates solvolyze one order of magnitude faster than methyl carbonates. Optimized geometries of 1LG and 2LG at B3LYP/6-311G(d,p), B3LYP/6-311++G(d,p), and MP2(full)/6-311++G(d,p) levels revealed that negative charge delocalization in carbonate anions to all three oxygen atoms occurs due to negative hyperconjugation. Phenyl carbonate (1LG) is a better leaving group (Nf = -0.84 ± 0.07 in 80% v/v aq EtOH) than methyl carbonate 2LG (Nf = -1.84 ± 0.07 in 80% v/v aq EtOH) because of more pronounced negative hyperconjugation, which is characterized with a more elongated RO-C bond and more increased RO-C-CO angle in 1LG than in 2LG. Calculated affinities of benzhydryl cation toward methyl and phenyl carbonate anions (ΔΔEaff = 11.7 kcal/mol at the B3LYP/6-311++G(d,p) level and ΔΔEaff = 2.7 kcal/mol at the PCM-B3LYP/6-311++G(d,p) level in methanol, respectively) showed that 1LG is more stabilized than 2LG, which is in accordance with greater solvolytic reactivity of 1 than 2.
Palladium-catalyzed nucleophilic substitution of diarylmethyl carbonates with malonate carbanions
Kuwano, Ryoichi,Kusano, Hiroki
, p. 528 - 529 (2008/02/10)
The nucleophilic substitution of diarylmethyl carbonates with malonate carbanions proceeded in the presence of [Pd(π-C3H 5)(cod)]BF4-Cy-Xantphos, giving the desired (diarylmethyl)malonates in up to 90% yield. The yield was extremely affected by choice of the phosphine ligand. Copyright
