Structurally-defined potassium-mediated regioselective zincation of amino- and alkoxy-substituted pyridines

Abstract

The new synergic base [PMDETA.K(TMP)(Et)Zn(Et)] selectively zincates 4-(dimethylamino)pyridine at the 2-position and 4-methoxypyridine at the 3-position, to afford bimetallic potassium pyridylzinc complexes each displaying a novel, but remarkably different, structure.

Assembly of ethylzincate compounds into supramolecular structures

“…Compound 1 is built up by Na þ and [ZnEt 2 Ph] À ions, and there seems to be only two previous structures of zincate-like species with ethyl ligands in the Cambridge Structural Database. These two structures are very different from 1, since they display functionalised R-groups and additional neutral ligands [21,22]. Both of these two compounds were, like 1, obtained by metallation of aromatic substrates.…”

Structurally Defined Potassium‐Mediated Zincation of Pyridine and 4‐R‐Substituted Pyridines (R=Et, iPr, tBu, Ph, and Me2N) by Using Dialkyl–TMP–Zincate Bases

“…For brevity, only the specific structures of 4 and 9 are shown (Figures 1 and 2, respectively) because they are representative of the complete series 3 – 9 . As in the case of previously reported 3 ,[10] structures 4 – 9 can be viewed as heterocyclic 9,10-dihydroanthracene mimics, each with a central diazadicarbadizinca (ZnCN) 2 ring, capped above and below by a potassium cation, which is complexed with a PMDETA ligand. All of these discrete molecules sit on crystallographically imposed inversion centers.…”

“…Diethyl reagent 1 and the butyl homologue 2 were obtained in solid (colorless and crystalline) form (in isolated yields of 61 and 20%, respectively) and were also identified from easily assignable 1 H and 13 C NMR spectra (see the Experimental Section for details). Adding to the database of potassium–zincate structures,[12] which is relatively sparse compared with those of other categories of alkali-metal organometallic compounds, the previously reported molecular structure of 1 [10] is depicted in Scheme 1. Designed based upon a KNZnC ring of four different atoms, terminal PMDETA (3×N) and Et (1×C) ligands on K and Zn, respectively, complete the structure.…”

“…Because the alkali metal plays a pivotal, albeit supporting, role in AMMZn methodology, and given that major distinctions exist between certain lithium, sodium, and potassium congeners in other classes of organometallic compounds, we decided to develop a complementary TMP–zincate chemistry of potassium. Our previously reported starting point was to introduce the diethyl derivative of the potassium–TMP–zincate [(pmdeta)K(μ-Et)(μ-tmp)Zn(Et)] ( 1 ) (PMDETA= N , N , N′ , N′′ , N′′ -pentamethyldiethylenetriamine) and to establish its potential as a synergic (potassium-zinc cooperative) zincating base through preliminary reactions with 4-(dimethylamino)pyridine and 4-methoxypyridine [10]. Herein, in an extension and elaboration of previous work, we report a systematic study of 1 with a wide range of pyridine substrates, comparing and contrasting its behavior in both stoichiometric and catalytic reactions with those of related potassium–dialkyl–TMP–zincates and potassium–trialkyl–zincates (TMP free).…”

Regio‐ und chemoselektive Metallierung von Arenen und Heteroarenen mit gehinderten Metallamidbasen

“…Kristalline Komplexe von solchen metallierten Spezies wurden isoliert und strukturell analysiert. [9,115,117] Des Weiteren enthüllten detaillierte mechanistische Untersuchungen, dass sowohl Na-TMP-Zinkate wie 74 (Schema 17) als auch Li-TMP-Zinkate wie 82 als Amidobasen wirken.…”