- Size-Induced Inversion of Selectivity in the Acylation of 1,2-Diols
-
Relative rates for the Lewis base-catalyzed acylation of aryl-substituted 1,2-diols with anhydrides differing in size have been determined by turnover-limited competition experiments and absolute kinetics measurements. Depending on the structure of the anhydride reagent, the secondary hydroxyl group of the 1,2-diol reacts faster than the primary one. This preference towards the secondary hydroxyl group is boosted in the second acylation step from the monoesters to the diester through size and additional steric effects. In absolute terms the first acylation step is found to be up to 35 times faster than the second one for the primary alcohols due to neighboring group effects.
- Mayr, Stefanie,Zipse, Hendrik
-
p. 18084 - 18092
(2021/12/02)
-
- Catalytic conversion of ketones to esters: Via C(O)-C bond cleavage under transition-metal free conditions
-
The catalytic conversion of ketones to esters via C(O)-C bond cleavage under transition-metal free conditions is reported. This catalytic process proceeds under solvent-free conditions and offers an easy operational procedure, broad substrate scope with excellent selectivity, and reaction scalability. This journal is
- Subaramanian, Murugan,Ramar, Palmurukan M.,Rana, Jagannath,Gupta, Virendra Kumar,Balaraman, Ekambaram
-
supporting information
p. 8143 - 8146
(2020/09/09)
-
- Synthesis of acyclic ketones by catalytic, bidirectional homologation of formaldehyde with nonstabilized diazoalkanes. Application of a chiral diazomethyl(pyrrolidine) in total syntheses of erythroxylon alkaloids
-
This work offers a catalytic approach to convergent ketone assembly based upon formal and tandem C-H insertion of diazoalkanes in the presence of limiting amounts of monomeric formaldehyde, which is easily generated as a gas by thermolysis of the inexpensive and abundant paraformaldehyde (~30 USD/kg). The method forms di-, tri-, and even tetrasubstituted acetones with high efficiency, and it has streamlined a synthesis of (-)-dihydrocuscohygrine in which the absolute stereochemistry of a proline-based starting material is preserved. Assisted by the advent of new protocols for hydrazone oxidation, we also provide full details on handling non-carbonyl-stabilized diazo compounds.
- Wommack, Andrew J.,Kingsbury, Jason S.
-
p. 10573 - 10587
(2013/11/19)
-
- Transition metal free oxidative esterification of alcohols with toluene
-
Using Bu4NI as the catalyst and tert-butyl hydroperoxide as the oxidant, direct esterification of alcohols with toluene derivatives was achieved. Mechanistic investigations indicate that the alcohols are sequentially oxidized to aldehydes, carboxylic acids, and then to benzyl esters. Bu 4N+ functions as a phasetransfer reagent and iodide catalyzes the reaction.
- Liu, Lianghui,Yun, Lin,Wang, Zikuan,Fu, Xuefeng,Yan, Chun-Hua
-
supporting information
p. 5383 - 5386
(2013/09/12)
-
- Benzylic-acetoxylation of alkylbenzenes with PhI(OAc)2 in the presence of catalytic amounts of TsNH2 and I2
-
Treatment of alkylbenzenes with (diacetoxyiodo)benzene in the presence of catalytic amounts of p-toluenesulfonamide or p-nitrobenzenesulfonamide, and molecular iodine in 1,2-dichloroethane at 60 °C gave the corresponding (α-acetoxy)alkylbenzenes in good to moderate yields. The present reaction is a simple method for the introduction of an acetoxy group to the benzylic position of alkylbenzenes.
- Baba, Haruka,Moriyama, Katsuhiko,Togo, Hideo
-
experimental part
p. 4303 - 4307
(2011/08/22)
-
- SuperQuat 5,5-dimethyl-4-iso-propyloxazolidin-2-one as a mimic of Evans 4-tert-butyloxazolidin-2-one
-
The incorporation of a gem-dimethyl group at the 5-position of a chiral oxazolidinone biases the conformation of the adjacent C(4)-stereodirecting group such that the gem-dimethyl-4-iso-propyl combination mimics a C(4)-tert-butyl group, providing higher levels of stereocontrol than a simple 4-iso-propyloxazolidinone. The generality of this principle is demonstrated with applications in stereoselective enolate alkylations, kinetic resolutions, Diels-Alder cycloadditions and Pd-catalysed asymmetric acetalisation reactions. The Royal Society of Chemistry 2006.
- Bull, Steven D.,Davies, Stephen G.,Garner, A. Christopher,Kruchinin, Dennis,Key, Min-Suk,Roberts, Paul M.,Savory, Edward D.,Smith, Andrew D.,Thomson, James E.
-
p. 2945 - 2964
(2008/02/09)
-
- Solubilizing agents for active or functional organic compounds
-
An active or functional organic compound is solubilized in a diaryl organic compound having a polar or polarizable functional group therein, as a solvent, cosolvent or additive, to form a composition thereof. Representative active or functional organic compounds include those present in personal care products, e.g., sunscreens containing UVA/UVB absorbing compounds, such as avobenzone, benzophenone-3, and 4-methylbenzylidene camphor. Such compositions also show increased SPF, UVA/UVB absorbance ratio, and critical wavelength performance properties.
- -
-
-
- The role of acyloxyphosphonium ions and the stereochemical influence of base in the phosphorane-mediated esterification of alcohols
-
Intimate details of the Mitsunobu mechanism: The trapping of an acyloxytributylphosphonium ion with a chiral secondary alcohol leads to either retention or inversion of stereochemistry in the resulting ester depending on the exclusion or inclusion of a base (see scheme). Insight into the mechanism of phosphorane-mediated esterification processes is presented.
- McNulty, James,Capretta, Alfredo,Laritchev, Vladimir,Dyck, Jeff,Robertson, Al J.
-
p. 4051 - 4054
(2007/10/03)
-