Stereoelectronic effects on reactivity. Crystal-structure–reactivity correlations for acetals with synperiplanar lone pairs
作者:P. Deslongchamps、P. G. Jones、S. Li、A. J. Kirby、S. Kuusela、Y. Ma
DOI:10.1039/a705142e
日期:——
in the acetal cleavage reaction. However, at least part of this increased reactivity towards hydrolysis must derive from the higher ground state energy of the boat conformation, and a careful examination of a series of compounds 3 reveals intriguing and systematic differences between the two systems. The spontaneous hydrolysis of the synperiplanar series shows extraordinarily high sensitivity to the
报道了一系列四氢吡喃基乙缩醛3的合成和五个晶体结构,其中四氢吡喃基环固定在对称的舟形结构中。四个芳基缩醛3的自发水解比四氢吡喃环在构象上可移动并因此自由采用椅子构象的相应化合物的水解快几倍。在缩醛裂解反应中,与反平面(ap)孤对相比,似乎没有立体电子阻碍滑膜(sp)参与。但是,这种增加的对水解的反应性的至少一部分必须来自船形结构的较高基态能量,对一系列化合物3的仔细检查显示了这两个系统之间的有趣和系统性差异。β LG = 1.4),具有用于轴向四氢吡喃基缩醛与antiperiplanar孤对已知已经很高的值进行比较。相反,键长相关性显示出降低的灵敏度。结果表明,在sp几何的基态中,n–σ * C–O相互作用(环内异头作用)较弱。