79560-59-1Relevant academic research and scientific papers
Tris(benzhydryl) and Cationic Bis(benzhydryl) Ln(III) Complexes: Exceptional Thermostability and Catalytic Activity in Olefin Hydroarylation and Hydrobenzylation with Substituted Pyridines
Selikhov, Alexander N.,Boronin, Egor N.,Cherkasov, Anton V.,Fukin, Georgy K.,Shavyrin, Andrey S.,Trifonov, Alexander A.
, p. 5432 - 5443 (2020/10/12)
A series of Ln(III) tris(benzhydryl) complexes [(p-tBu-C6H4)2CH]3Ln (Ln=La (1), Nd (2), Y (3)) were synthesized by the salt metathesis reactions of LnHal3(THF)3.5 (Ln=La, Nd, Hal=Cl; Ln=Y, Hal=I) and [(p-tBu-C6H4)2CH]Na. In 1–3 the benzhydryl ligands are linked with the metal centres in η4-coordination mode. For diamagnetic complexes 1 and 3 a fluxional behaviour was detected in solution. Complexes 1–3 proved to be thermally stable: no decomposition was observed even after heating their solutions in toluene-d8 at 140 °C during 72 h. The reactions of 1 and 2 with B(C6F5)3 allowed for the synthesis of base-free cationic complexes [(p-tBu-C6H4)2CH]2Ln[(p-tBu-C6H4)2CHB(C6F5)3] (Ln=La (4), Nd (5)) which adopt the structure of a contact ion pair. Combinations of 1–3 and borane ((B(C6F5)3, [Me2NHPh][B(C6F5)4], [Ph3C][B(C6F5)4]) as well as 4 and 5 were found to be highly efficient, regio- and chemoselective catalysts for hydroarylation and hydrobenzylation of C=C bonds of a variety of substrates with substituted pyridines. These catalysts enable highly challenging transformations such as hydrobenzylation of 1,1-disubstituted and internal C=C bonds. (Figure presented.).
PYRIDINES. PARTIE IX - PLURIBENZYLATION DE LA S-COLLIDINE ET DE LA LUTIDINE-2,6
Compagnon, Paul-Louis,Kimny, Tan,Gasquez, Francoise
, p. 803 - 816 (2007/10/02)
A literature survey of the polymetalation of 2,6-lutidine 2 shows different results about the site(s) of deprotonation and condensation with various electrophiles.This discrepancy prompts us to examine the polylithiation (PhLi 3 equivalents, Et2O) of s-collidine 1, 2,6-lutidine 2 and more briefly of 2,4-lutidine 3.Polylithiation takes place exclusively at the methyl groups of the same position vs the ring nitrogen : 2- and/or 6-methyl of 1.The previous regioselectivity observed in the case of the monometalation in Et2O is maintained.From 1 and 2, polylithiation gives picolyl anions which lead by reaction with PhCH2Cl, simultaneously to mono-, di-symmetrical, di-non-symmetrical α-derivatives, and tri- and tetra-symmetrical α,α'-compounds; but no product is formed from a benzylic β-anion.In the same way, the deprotonation of 2-methyl-6-(2-phenylethyl) pyridine 17 leads to 2,6-bis (2-phenylethyl) pyridine 19 and 2-methyl-6-dibenzylmethyl pyridine 18, to the exclusion of the β-compound 2-methyl-6-(2,3-diphenylpropyl) pyridine 21.The latter compound is formed in low yield, besides 19 and 18, in the conditions of the Tchitchibabine reaction (NaNH2, toluene).The structure of the benzylated compounds was established mainly from the 1H-nmr data.No product was isolated which would result from the nucleophilic attack of the generated carbanions at the pyridine carbons.
