An Efficient Modular Synthesis of Conjugated ω-(<b><i>p-</i></b>Hexyloxyphenyl)-polyenals
作者:Kazimiera Wilk、Beata Domagalska、Ludwik Syper
DOI:10.1055/s-2001-18711
日期:——
Convenient precursors (α,β-unsaturated aldehydes 1-5) for all-E conjugated Ï-(p-hexyloxyphenyl)polyenals having two (15), four (16), five, (19), six (17) and eight (18) conjugated double bonds were synthesized in a modular synthesis using reactive silyl enol ethers [1-(trimethylsilyloxy)-1,3-butadiene or 1-(trimethylsilyloxy)-1,3,5-hexatriene)] as building blocks, and 5,5-diethoxypenta-2-enal (1) as a template. Polyene 8 containing three conjugated double bonds in its structure was obtained from Ï-(p-hexyloxyphenyl)propenal (6) and butadienyl ethyl ether as starting materials.
conjugated dienes undergo 1,2 and 1,4 cycloaddition to diphenylketene to give cyclobutanones and dihydropyrans by a two-step ionic process. The electron delocalization of ketenophiles plays a prominent part in the mechanism but it is difficult to show a quantitative relation between second order rate constants and electronic distribution computed by the CNDO/2 method. The Z and E isomers of dienes give different
通过两步离子过程,功能共轭二烯经过1,2和1,4环加成成二苯乙烯酮,得到环丁酮和二氢吡喃。酮基亲电子的电子离域作用在该机理中起着重要作用,但是很难显示二阶速率常数与通过CNDO / 2方法计算出的电子分布之间的定量关系。二烯的Z和E异构体给出不同的加合物,速率常数比k E / k Z与过渡态稳定有关。