Synthesis and cathodic cleavage of a set of substituted benzenesulfonamides including the corresponding tert-butyl sulfonylcarbamates: pK a of sulfonamides
摘要:
From a series of Substituted benzenesulfonic acids, most of which have previously been employed for the protection of amino functions and including a few such known to facilitate cleavage by acid, benzylamides 1a-k have been derived and studied. Initially their electrochemical cleavage potentials were determined by cyclic voltammetry in order to further explore selective deprotection within this substance group. In parallel, the corresponding tert-butyl sulfonylcarbamates 2a-k have also been prepared and studied. Among the sulfonamides investigated S-N bond cleavage was found to take place over a wide range of potentials from -1.67 to -2.64 V (excluding the nitro derivative), the most acid-labile groups requiring more negative potentials, whereas this cleavage was facilitated by 0.19-0.30 V for the sulfonylcarbamates. Small scale electrolyses of 2 at controlled potential with determination of the cleavage products formed were subsequently performed. For the N-benzylbenzenesulfonamides 1, the pK(a)s in DMSO and in some cases also in water have been determined and found to be in the range 14.0-16.4 and 10.07-11.53, respectively.
Mild, efficient cleavage of arenesulfonamides by magnesium reduction
作者:Barthélémy Nyasse、Leif Grehn、Ulf Ragnarsson
DOI:10.1039/a701408b
日期:——
The cleavage of arenesulfonamides via
N-arenesulfonylcarbamates is achieved within a few minutes under
ultrasonic conditions by reaction with magnesium in anhydrous
methanol.
Synthesis and cathodic cleavage of a set of substituted benzenesulfonamides including the corresponding tert-butyl sulfonylcarbamates: pK a of sulfonamides
作者:Barth�l�my Nyasse、Leif Grehn、Ulf Ragnarsson、Hernani L. S. Maia、Luis S. Monteiro、Ivo Leito、Ilmar Koppel、Juta Koppel
DOI:10.1039/p19950002025
日期:——
From a series of Substituted benzenesulfonic acids, most of which have previously been employed for the protection of amino functions and including a few such known to facilitate cleavage by acid, benzylamides 1a-k have been derived and studied. Initially their electrochemical cleavage potentials were determined by cyclic voltammetry in order to further explore selective deprotection within this substance group. In parallel, the corresponding tert-butyl sulfonylcarbamates 2a-k have also been prepared and studied. Among the sulfonamides investigated S-N bond cleavage was found to take place over a wide range of potentials from -1.67 to -2.64 V (excluding the nitro derivative), the most acid-labile groups requiring more negative potentials, whereas this cleavage was facilitated by 0.19-0.30 V for the sulfonylcarbamates. Small scale electrolyses of 2 at controlled potential with determination of the cleavage products formed were subsequently performed. For the N-benzylbenzenesulfonamides 1, the pK(a)s in DMSO and in some cases also in water have been determined and found to be in the range 14.0-16.4 and 10.07-11.53, respectively.
Silver-Catalyzed Enantioselective Mannich Reaction of Diazoacetate Esters with <i>N</i>-Boc Aldimines
作者:Gerard P. Robertson、Alistair J. M. Farley、Darren J. Dixon
DOI:10.1021/acs.joc.9b03177
日期:2020.2.21
The highlyenantioselective Mannich reaction of diazoacetate esters with N-Boc aldimines catalyzed by silver(I) triflate in the presence of (R)-DM-SEGPHOS is reported. The reaction is broad in scope with respect to the (hetero)aromatic aldehyde-derived aldimine and tolerates significant variability of the diazoacetate ester component. Yields and enantioselectivities are good to excellent, and the reaction