Method Evans

The Evans method gives spiro-oxetane 30 when 2-propenylcyclohexanol (29) is employed as the substrate. 

The Evans method (88S862) affords 2-iodomethyl-l,4-dioxane when alcohol 257 is subjected to this cyclization process (Eq. 41). 

Diastereoselective reduction by chemical methods For the preparation of both enantiomers of dihydroxy ester sy -5a Prasad s [19] sy -selective borohydride reduction was applied, giving dihydroxy esters syn-5a in a diastereomeric ratio of dFsy a ti = 28 1 to 45 1. The enantiomers of dihydroxy ester anti-Sa were synthesized according to Evans method [20], which resulted in dr = 14 1 to 18 1... 

The Evans method gives excellent results provided adequate care is taken. A most important requirement is that the solution temperature is measured reliably. One effective means of accomplishing this for H NMR is to insert into the NMR tube a capillary or additional coaxial sample of an NMR temperature calibrant solvent, usually methanol (158) or ethylene glycol (88). In this way the temperature measurement is made simultaneously with the susceptibility measurement. A second important factor is the variation of the solvent density with temperature (126). Because the density difference between the solvent and solution depends linearly on the concentration of the solute, it is only... 

Fig. 1. Linear plot of solution magnetic susceptibility obtained by the Evans method.

C. Rice-Evans, Methods to quantify antioxidant activity of tea/tea extracts in vitro, Crit. Rev. FoodNutr., 2001, 41, 405 107. 

Analysis of [Ni(salpd)] Magnetic Moment in Solution—Evans Method... 

Various adaptations that rely on force methods have been commercialised (the so-called Evans-Johnson-Matthey balance) or designed from readily available parts and described in the literature. The Evans method uses NMR and can provide variable temperature data on molecules in solution, but the technique is limited to a window where solvents stay liquid and solutes stay in solution. The one development that has been crucial to the more recent rapid development of this research field is the availability of relatively inexpensive and easy-to-use, variable temperature, variable field instrumentation, specifically the Superconducting Quantum Interference Device (SQUID) magnetometer. With a SQUID, it is possible, even for relatively inexperienced users, to determine the magnetic properties of a sample (typically 10-20 mg) as a function of temperature and applied field (down to 1.8 K and... 

---