108791-64-6Relevant articles and documents
4-Hydroxyphenacyl Ammonium Salts: A Photoremovable Protecting Group for Amines in Aqueous Solutions
Bownik, Iwona,?ebej, Peter,Literák, Jaromír,Heger, Dominik,?imek, Zdeněk,Givens, Richard S.,Klán, Petr
, p. 9713 - 9721 (2015/10/12)
Irradiation of N-protected p-hydroxyphenacyl (pHP) ammonium caged derivatives at 313 nm releases primary and secondary amines or ammonia in nearly quantitative yields via the photo-Favorskii reaction when conducted in acidic or neutral aqueous buffered media. The reaction efficiencies are strongly dependent on the pH with the most efficient and highest yields obtained when the pH of the media maintains the ammonium and p-hydroxyl groups as their conjugate acids. For example, the overall quantum yields of simple secondary amines release are 0.5 at acidic pH from 3.9 to 6.6 dropping to 0.1 at neutral pH 7.0 and 0.01 at pH 8.4. Speciation studies provide an acid-base profile that helps define the scope and limitations of the reaction. When the pKa of the ammonium group is lower than that of the phenolic hydroxyl group, as is the case for the α-amino-protected amino acids, the more acidic ammonium ion deprotonates as the media pH is changed from acidic toward neutral or basic, thus diminishing the leaving group ability of the amino group. This, in turn, lowers the propensity for the photo-Favorskii rearrangement reaction to occur and opens the reaction pathway to alternative competing photoreduction process.
Carbon-Carbon Bond Formation Using Hypervalent Iodine Under Lewis Acid Conditions: Scope of the Method for the Synthesis of Butane-1,4-diones
Moriarty, Robert,Prakash, Om,Duncan, Michael P.
, p. 559 - 562 (2007/10/02)
Hypervalent iodine oxidation of the silyl enol ethers of various acetophenones (2a-g), 2-acetylthiophenes (2i-k), 2-acetylfuran (2l) and 2-acetylbenzofuran (2m) with iodosobenzene-boron trifluoride-diethyl ether results in carbon-carbon coupling to yield the corresponding 1,4-disubstituted butane-1,4-dione (3a-m).Cross coupling (dissimilar coupling) between 4-methoxyacetophenone silyl enol ether (2c) and 4-nitroacetophenone silyl enol ether (2e) affords 1-(4-methoxyphenyl)-4-(4-nitrophenyl)butane-1,4-dione (27percent); the other minor products (3c) (18percent) and (3e) (15percent) resulting from similar coupling in this reaction.The sterically hindered aliphatic silyl enol ether (2h) obtained from pinacolone also undergoes smooth coupling whereas other aliphatic ketones do not.This method is likewise unsuccessful in case of nitrogen-containing heterocycles, viz. 2-,3-,4-acetylpyridine silyl enol ethers and tropinone silyl enol ether.
