Minimization of Organocuprate Complexity through Self‐Organization: Remarkable Orientation Effect in Mixed Cuprate π Complexes

Abstract

A great deal of effort has gone into the research, development and application of mixed organocuprate(I) reagents [R T R NT CuLi]. [1][2][3][4][5][6][7] These "mixed cuprates" contain one group R T that is transferred to a substrate and a second, nontransferred group R NT (sometimes called a "dummy ligand") that is assumed to be inert under the reaction conditions. They were introduced in order to solve the efficiency problem of homocuprates R 2 CuLi (Gilman reagents), which only transfer one equivalent of the R-group in most applications. Outstanding examples include thienyl (Th), [2] cyano, [3] alkynyl, [4] thiolato, [5] trimethylsilylmethyl, [6] and phosphido [7] groups.We have found that upon addition of typical a,bunsaturated ketones, esters, nitriles, or sulfones, these mixed cuprates give p complexes that exhibit a remarkable orientation effect in which R T is cis to the site of the usual addition reaction, for example, the b-carbon in a,b-unsaturated carbonyl compounds 1 (Scheme 1). Complexes with C À N and C À S double bonds also display this effect. The selforganization we report here substantially reduces the com-plexity of mixed organocuprate reagents, and it is essential for a complete understanding of their reaction mechanisms.

First X‐Ray Crystal Structure and Internal Reference Diffusion‐Ordered NMR Spectroscopy Study of the Prototypical Posner Reagent, MeCu(SPh)Li(THF)3

“…[11] Preparation of NMR samples has been described. [10,16] For details of the molecular weight measurements, see the Supporting Information. Reference compounds (internal standards) [21] for these diffusion-ordered NMR studies are shown below: CCDC-928158 (1) contains the supplementary crystallographic data for this paper.…”

“…[14,15] Solvent-separated ion pairs (SSIP) are present in THF, and contact ion pairs (CIP) are favored in diethyl ether, where the CIP is a dimer. [14] The X-ray structure of 1 ( Figure 1) shows that in the solid state, the CIP is a monomer, which suggests that it might also be monoA We have previously studied MeCuA C H T U N G T R E N N U N G (SPh)Li and some of its p-complexes in [D 8 ]THF solution, [16] but did not address the issue of solvation. To explore the solution structure of selected organocuprates, apparent molecular weights were determined by using the internal reference diffusion-ordered NMR method of Williard and co-workers.…”

The X‐ray Crystal Structure of a Cuprate–Carbonyl π‐Complex

“…Therefore, dialkyl cuprate complexes of double-bonds can be described as pseudo square-planar, which was originally proposed on the basis of NMR spectroscopy. [7,8] Also noteworthy is the approximately tetrahedral lithium atom, bonded to the cuprated carbonyl group as well as three tetrahydrofuran (THF) ligands. The former lithium-oxygen bond length is significantly less than the latter bond lengths (see Figure 1 caption).…”

“…Trans coupling across copper is typically larger than cis. [5][6][7][8][9] A heteronuclear multiple quantum coherence plot (HMQC, Figure 3, right) has a cross-peak (lower right quadrant) between the upfield methyl hydrogen atoms (d = À1.54 ppm) and the downfield methyl carbon (d = 6.04 ppm), which are assigned to Me b . It is highly unusual for the 1 H NMR shift of Me b to be the upfield signal.…”