694-65-5Relevant academic research and scientific papers
Theoretical and experimental studies of cycloconjugation involving second-row elements
Fraenkel, Gideon,Kolp, Christopher J.,Chow, Albert
, p. 4307 - 4314 (1992)
In a method proposed to investigate conjugative interactions between second-row elements (S, P) amd a π-electron system, barriers to amide rotation have been measured using NMR line-shape methods, for N-acetyl-4-X(hetero)-1,4-dihydropyridines (X = SO2,7; P(O)OCH3,13; C(CH3)2, 6 (reference)) as well as the dihydro (8a) and tetrahydro (9) derivatives, respectively, of 7. It is suggested that such interactions would stabilize the transition states for amide rotation by cycloconjugation but not the planar equilibrium states, compressing the barriers relative to reference 6. In fact, amide barriers in 7,13, and N-acetylpyrrole are substantially (>6 kcal) less than in 6, 8ab, and 9, all ca. 17 kcal, in all of which saturated centers interrupt possible cycloconjugation. These conclusions are supported by the results of ab initio calculations at the Hartree-Fock level with the 3-21G(*) basis set.
Microwave-assisted direct esterification of cyclic phosphinic acids in the presence of ionic liquids
Kiss, Nóra Zsuzsa,Keglevich, Gy?rgy
, p. 971 - 974 (2016/02/16)
The efficiency of the microwave-assisted direct esterification of cyclic phosphinic acids was significantly enhanced by adding 10% of an ionic liquid to the reaction mixture prior to irradiation. In the presence of [bmim][PF6] most of the esterifications were complete within 30 min at 180 °C.
