Kinetic and Mechanistic Studies of the Formal (1+2)- and (1+4)-Cycloadditions of Germylenes to Conjugated Dienes
作者:Lawrence A. Huck、William J. Leigh
DOI:10.1021/om900791e
日期:2009.12.14
1-diaryl-2-vinylgermiranes (6a−g) resulting from formal (1+2)-cycloaddition to the less-substituted C═C bond of the diene. These compounds are formed reversibly and with rate constants in excess of 109 M−1 s−1, and appear as discrete reaction intermediates exhibiting λmax = 285 nm and lifetimes of 2−670 μs depending on the identity of the germylene and the diene. The variations in the lifetimes with aryl substituents
异戊二烯和2,3-二甲基-1,3-丁二烯(DMB)与二苯基亚反应的快速动力学研究(GePh 2,图2a),并用一系列diarylgermylenes带有极性取代基的环(齿轮的异戊二烯的2,2B -克)已在己烷溶液中进行。尽管与异戊二烯反应的主要稳定产物是相应的1,1-二芳基锗环戊-3-烯衍生物,但结果表明,主要的初始产物是相应的瞬态1,1-二芳基-2-乙烯基germiranes(6a - g)是由于二烯的取代度较低的C═C键上形成了正式的(1 + 2)-环加成反应。这些化合物可逆地形成,速率常数超过10 9 M -1 s -1,并以离散的反应中间体形式出现,具有λmax= 285 nm,且寿命为2-670μs,这取决于亚二甲苯基和二烯的身份。研究表明,芳基取代基的寿命变化与乙烯基Germirane→生殖环戊3烯异构化的逐步机理最一致,该机理涉及(可逆)离解为游离的次二甲苯和二烯,然后(不可逆)解离(1