Structure Identification of Precatalytic Copper Phosphoramidite Complexes in Solution

Abstract

Copper salts and organocopper(I) compounds are widely used for stoichiometric and catalytic additions and substitutions. [1][2][3] The high synthetic potential of copper(I) complexes or metal organocuprate clusters and the difficulty in designing new active copper systems are both based on the ability of these complexes to form supramolecular clusters, which represent an intricate example of molecular recognition.

Improved applicability of DOSY experiments by high resolution probes combined with gradient amplifiers of diffusion units

“…[17] For each parameter combination, the maximum intensity calculated with 160.5 Gauss/cm was divided by the maximum intensity of 53.5 Gauss/cm, which results in an enhancement factor represented by one point in Fig. 3.…”

“…This ligand had also been used in our previous diffusion studies. [17,21,22] For the experiments with 1 in deuterated tetrahydrofuran, two temperatures (288 and 235 K) were selected to simulate typical pairs of diffusion coefficients and relaxation properties of small molecules or large assemblies, and to test the effect of reduced transversal and longitudinal relaxation times. As pulse sequence the double-stimulated-echo sequence with bipolar gradient pulses A (Fig.…”

“…In addition, low temperature measurements are not yet possible with these diffusion probes and broad band channels are not available. In contrast, high gradient strengths combined with the positive properties of high resolution probes (high 1 H resolution, flexible temperature, and multinuclear applications) would have the potential to enable or to facilitate the DOSY studies on proteins, supramolecular systems, and organometallic complexes, such as our investigations on organocuprate structures [5,7] and intermediates, [19,20] and precatalytic phosphoramidite-copper complexes [17,21,22] at temperatures between 240 and 180 K.…”

“…1, as found for some organocuprates [16] or phosphoramidite-copper complexes. [17] Also for samples with better relaxation properties, often experimental times of several hours per DOSY spectrum are required, particularly in the case of 31 P-DOSY applications. [18] To measure reliable low temperature DOSY results with the Müller-Jerschow pulse sequence in a tolerable period of time with this kind of substances, it is necessary to apply high gradient strengths or at minimum a fast and efficient parameter optimization with respect to the specific relaxation properties of the sample.…”

Conversion of Propargylic Alcohols to β‐Oxo Esters Catalyzed by Novel Ruthenium‐Phosphoramidite Complexes

“…[10] The nature of the catalytically active species for these in situ catalyst systems is not always known. [11] Phosphoramidites derived from BINOL (1,1'-binaphthyl-2,2'-diol) are the most prevalent, but others utilizing TADDOL, e.g., are known as well. [12] It has been shown that changes at the phosphoramidite skeleton have a profound impact on yields and enantioselectivities in catalytic applications of these ligands.…”