128749-93-9Relevant academic research and scientific papers
Mechanistic and Preparative Studies on the Regio- and Stereoselective Paraffin Hydroxylation with Peracids
Schneider, Hans-Joerg,Mueller, Walter
, p. 4609 - 4615 (1985)
Reactions of more than 20 hydrocarbons with p-nitro- or, e.g., 3,5-dinitroperbenzoic acid in chloroform show regioselectivities of Rst = 90 (relative rates of attack at tertiary and secondary C-H bonds, after statistical correction) to 500 and configurational retention, if applicable, of typically 97-99.7percent.Radical side reactions are recognized by concomitant formation of, e.g., nitrobenzene and are responsible for a decrease in regio- and stereoselectivity.Steric effects are observed in attack at axial tertiary C-H bonds and at bridgehead positions.Electronegative and hydrogen-bonding substituents in the alkane diminish, and alkyl groups enhance the rates; the observed Taft ρ* value of -2.2 indicates substantial positive charge accumulation in the transition state in agreement with the high regioselectivity.A Hammett reaction constant of +0.63 is obtained from substituted perbenzoic acids; activation parameters of ΔH* = 15-19 kcal mol-1 and ΔS* = -22 to -29 eu with three alkanes of different flexibility and an isotope effect of kH/kD = 2.2 with methylcyclohexane are measured.Aromatic rings are usually not attacked but lead to deactivation of the peracid even at remote alkane C-H positions; similar deactivation is found in hydrogen-bonding solvents.Androstanes yield preferentially 9α- and 5α-hydroxy products, if, e.g., a 17β-acetoxy substituent is used to steer the reaction.Diols usually are only observed as a result of a proximity effect of a peracid associated at the first formed hydroxy group.The results point to relatively late and oxenoid transition states with substantial charge separation in the substrate.Attempts to achieve selective oxidations using macrocyclic azacyclophanes with attached carboxylic functions were not successful, although the host compounds showed selective complexation of hydrocarbons.
Selective C-H bond hydroxylation of cyclohexanes in water by supramolecular control
Yang, Bin,Cui, Jian-Fang,Wong, Man Kin
, p. 30886 - 30893 (2017/07/07)
A new approach for selective hydroxylation of non-activated cyclohexanes using dioxirane generated in situ in water through supramolecular control has been developed. Using β-CD and γ-CD as the supramolecular hosts, selective hydroxylation of cyclohexane substrates, including trans/cis-1,4-, 1,3-and 1,2-dimethylcyclohexanes and trans/cis-decahydronaphthalene, was achieved in up to 54% yield in water. Furthermore, site-selective C-H bond hydroxylation of (+)-menthol was achieved by obstructing the approach of dioxirane to the C-H bond with higher steric hindrance through inclusion complexation with β-CD and γ-CD in water.
Stereoselective dioxirane hydroxylations and the synthesis of tripod boronic acid esters
D'Accolti, Lucia,Fiorentino, Michele,Fusco, Caterina,Capitelli, Francesco,Curci, Ruggero
, p. 3575 - 3578 (2007/10/03)
Methyl(trifluoromethyl)dioxirane (TFDO, 1b), a powerful yet selective oxidant, was employed to achieve in high yield the direct stereoselective hydroxylation at tert-CH of cis,cis-1,3,5-trimethylcyclohexane (4), yielding triol 7 bearing all-axial disposit
Cyclohexane-based 1,3-Dipodands; Complexation and Conformational Biasing
Shirodkar, Shailaja M.,Weisman, Gary R.
, p. 236 - 238 (2007/10/02)
Cyclohexane-based cis-1,3-dipodand (1) undergoes ring inversion to a diaxial conformation upon Na(1+) complexation, while related diaxially biased dipodand (2) is a better host.
