The molecular structure of 4-tert-butylpyrazoles in the solid state and in solution: an X-ray, NMR and calorimetric study of the buttressing effect of a 4-tert-butyl substituent
作者:Swiatoslaw Trofimenko、Arnold L. Rheingold、Louise M. Liable-Sands、Rosa María Claramunt、Concepción López、María Dolores Santa María、Jose Elguero
DOI:10.1039/b101733k
日期:——
The
molecular structures of three 4-tert-butylpyrazoles have been determined at 173 K: 4-tert-butyl-3(5)-isopropylpyrazole
1, 4-tert-butyl-3(5)-neopentylpyrazole 2 and 4-tert-butyl-3(5)-p-tolylpyrazole 3. 1H, 13C and 15N NMR spectroscopies,
in solution and in the solid state (CPMAS), have been used to complement the structural information. The major
tautomers in solution correspond to the tautomers present in the crystal: 5-isopropyl 1b, 5-neopentyl 2b and 3-p-tolyl
3a. All these compounds crystallise as tetramers, formed by four identical tautomers, through N–H···N hydrogen bonds,
the tetramers corresponding to 1b and 2b
being folded
but that of 3a is the first example of a planar tetramer.
在 173 K 下测定了三种 4-叔丁基吡唑的分子结构:4-叔丁基-3(5)-异丙基吡唑 1、4-叔丁基-3(5)-新戊基吡唑 2 和 4-叔丁基-3(5)-对甲苯基吡唑 3。溶液和固态(CPMAS)的 1H、13C 和 15N NMR 光谱被用来补充结构信息。溶液中的主要同系物与晶体中的同系物相对应:5-异丙基 1b、5-新戊基 2b 和 3-对甲苯基 3a。所有这些化合物的晶体都是由四个相同的同系物通过 N-H-N 氢键形成的四聚体,其中 1b 和 2b 的四聚体是折叠的,而 3a 的四聚体则是第一个平面四聚体的例子。