RESUMO
We herein report the reaction of arylallenes with tris(pentafluorophenyl)borane that yields pentafluorophenyl substituted indenes. The tris(pentafluorophenyl)borane induces the cyclization of the allene and transfers a pentafluorophenyl ring in the course of this reaction. A Hammett plot analysis and DFT computations indicate a 1,1-carboboration to be the C-C bond-forming step.
RESUMO
The metal-free cis selective hydrogenation of alkynes catalyzed by a boroxypyridine is reported. A variety of internal alkynes are hydrogenated at 80 °C under 5â bar H2 with good yields and stereoselectivity. Furthermore, the catalyst described herein enables the first metal-free semihydrogenation of terminal alkynes. Mechanistic investigations, substantiated by DFT computations, reveal that the mode of action by which the boroxypyridine activates H2 is reminiscent of the reactivity of an intramolecular frustrated Lewis pair. However, it is the change in the coordination mode of the boroxypyridine upon H2 activation that allows the dissociation of the formed pyridone borane complex and subsequent hydroboration of an alkyne. This change in the coordination mode upon bond activation is described by the term boron-ligand cooperation.
RESUMO
We have developed a synthesis of 1,2-substituted adamantane carboxylic acids and further bridged cycloalkanes (cage compounds) by palladium acetate-catalyzed C-H bond oxidation. Acetoxylation of cycloalkane framework was performed using picolylamide as a directing group. Modification of the substrate, ligand design and variation of reaction conditions enabled us to study the mechanism of acetoxylation of aliphatic compounds. Post-functionalization reactions and cleavage of the directing group were developed. For the first time the synthesis and characterization of a ß-C3 -tri-substituted adamantane derivatives was achieved.
