Non‐Bonding 1,4‐Sulphur‐Oxygen Interaction Governs the Reactivity of α‐Ketothioesters in Triphenylphosphine‐Catalyzed Cyclization with Acetylenedicarboxylates
作者:Abhijit Bankura、Jayanta Saha、Rajib Maity、Indrajit Das
DOI:10.1002/adsc.202001376
日期:2021.2.16
1,4‐interaction involving C−S σ* orbital on the sulphur atom and the lone pair of electrons in the electron‐donating oxygen atom. This is apparent from the X‐ray crystallographically determined internuclear distance between the sulphur and ketone (C=O) oxygen atoms (2.71–2.85 Å), which is significantly less than the sum of their van der Waals radii (3.25–3.30 Å). The substitution on the S atom is oriented
α-酮硫酯经过三苯基膦(PPh 3)与乙二酮酸酯的催化环化反应平稳,而α-酮氧酸酯则需要更苛刻的条件和有限的底物范围。该反应可与各种α-酮硫代酯很好地结合,以中等至极好的收率提供高度官能化的α,β-不饱和γ-丁内酯。硫酯衍生物的较高反应性似乎是由于有利的分子内非键合静电1,4-相互作用,涉及硫原子上的Cσσ*轨道和给电子氧原子中的孤对电子。从X射线晶体学确定的硫和酮(C = O)氧原子之间的核间距离(2.71-2.85Å)可以明显看出,该距离明显小于其范德华半径的总和(3.25-3.30Å) 。S原子上的取代沿直径方向远离酮O原子,以使它们之间的相互作用最大化。γ-丁内酯产品中S与呋喃O原子(2.70Å)之间的1,4-S⋅⋅⋅O接触也可以看到这种趋势。