|
The Pauson–Khand reaction (or PKR or PK-type reaction) is a chemical reaction described as a The reaction was discovered by Ihsan Ullah Khand (1935-1980), who was working as a postdoctoral associate with Peter Ludwig Pauson (1925-2013)〔H. Werner. ''Angew. Chem. Int. Ed.'' 2014, ''53'', 3309. 〕 at the University of Strathclyde in Glasgow. This reaction was originally mediated by stoichiometric amounts of dicobalt octacarbonyl, but newer versions are both more efficient and catalytic.〔Schore, N. E. "The Pauson–Khand Cycloaddition Reaction for Synthesis of Cyclopentenones" ''Org. React.'', 1991, ''40'', 1. 〕〔S. E. Gibson and A. Stevenazzi "The Pauson–Khand Reaction: the Catalytic Age Is Here!" ''Angew. Chem. Int. Ed.'', 2003, 42, 1800-1810. 〕 With unsymmetrical alkenes or alkynes, regioselectivity can be problematic, but less so with intramolecular reactions. The reaction works with both terminal and internal alkynes although internal alkynes tend to give lower yields. The order of reactivity for the alkene is strained cyclic alkene > terminal alkene > disubstituted alkene > trisubstituted alkene. Unsuitable alkenes are tetrasubstituted alkenes and alkenes with strongly electron withdrawing groups.〔''Strategic applications of named reactions in organic synthesis: background and details mechanisms'' 2007 László Kürti,Barbara Czakó〕 ==Variations== Wilkinson's catalyst, based on the transition metal rhodium, also effectively catalyses PK reactions but requires silver triflate as a co-catalyst.〔Nakcheol Jeong, Byung Ki Sung, Jin Sung Kim, Soon Bong Park,Sung Deok Seo, Jin Young Shin, Kyu Yeol In, Yoon Kyung Choi ''Pauson–Khand-type reaction mediated by Rh(I) catalysts'' ''Pure Appl. Chem.'', Vol. 74, No. 1, pp. 85–91, 2002. ((Online article ))〕 Molybdenum hexacarbonyl is a carbon monoxide donor in PK-type reactions between allenes and alkynes with dimethyl sulfoxide in toluene. Cyclobutadiene also lends itself to a 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Pauson–Khand reaction」の詳細全文を読む スポンサード リンク
|