Novel η³-Allylpalladium−Pyridinylpyrazole Complex:  Synthesis, Reactivity, and Catalytic Activity for Cyclopropanation of Ketene Silyl Acetal with Allylic Acetates

Abstract

Novel cationic η3-allylpalladium−pyridinylpyrazole complexes 1a and 1b were synthesized from 3-alkyl-5-(2-pyridinyl)pyrazole and η3-allylpalladium chloride dimer in the presence of AgBF4. Cationic complexes 1a and 1b were converted into neutral complexes 2a and 2b under basic conditions. These complexes were characterized by 1H, 13C, and 15N NMR studies. Neutral complexes 2a and 2b have high catalytic activity for cyclopropanation of ketene silyl acetals with allylic acetates. Comparison of the cationic and neutral complexes and the reaction mechanism of cyclopropanation were discussed.

Phosphorescent Dyes for Organic Light‐Emitting Diodes

“…[23] In contrast, preparation of tert-butyl-substituted L 2 can be achieved through the condensation of methyl picolinate with pinacolone, followed by treatment with anhydrous hydrazine under similar condition. [24] The isoqunioline-substituted derivatives L 5 and L 6, which are useful for tuning the emission to longer wavelength region, were prepared from their 2-isoquinolyl reagents. Finally, C-linked 2-pyridyl-1,2,4-triazoles were synthesized according to literature methods, in which the CF 3 -substituted 1,2,4-triazole L 3 was easily obtained by using 2-pyridinecarboximidamide hydrochloride and trifluoroacetic acid hydrazide; the latter is obtained by reacting ethyl trifluoroacetate with hydrazine.…”

β‐Protic Pyrazole and N‐Heterocyclic Carbene Complexes: Synthesis, Properties, and Metal–Ligand Cooperative Bifunctional Catalysis

“…[14] Deprotonation coupled with coordination and dissociation at the metal center is also intriguing in terms of the bifunctional catalysis. Lam and co-workers demonstrated that the dehydrochlorination of the square-planar protic pyrazole complex 17 affords the pyrazolato-bridged dinuclear complex 18 (Scheme 7).…”

“…[42] Much earlier, Satake and co-workers demonstrated that the protic pyridylpyrazole complex 35 promotes cyclopropanation of ketene silyl acetals with allylic acetates (Scheme 14). [14] The reactions using the N-methylated pyra-…”

15N NMR coordination shifts in Pd(II), Pt(II), Au(III), Co(III), Rh(III), Ir(III), Pd(IV), and Pt(IV) complexes with pyridine, 2,2′-bipyridine, 1,10-phenanthroline, quinoline, isoquinoline, 2,2′-biquinoline, 2,2′:6′, 2′-terpyridine and their alkyl or aryl

“…NMR coordination shifts in Pd(II), Pt(II), Au(III), Co(III), Rh(III), Ir(III), Pd(IV), and Pt(IV) complexes [9] and +225.3, +218.7 ppm, [10] respectively, by subtracting 358.1 ppm relative shift. [6] c Versus free 2-(3 -methyl-5 -pyrazolyl)-py in CD 2 Cl 2 + CD 3 OD 1 : 1: δ 15N lig = −84.9 ppm (+273.2 ppm with respect to NH 4 NO 3 in DMSO-d 6 ).…”

“…[17] The variability of | 15N coord | parameters with the change of azine ligand is rather limited. Particularly, the introduction of alkyl or aryl side groups into the py, bpy or phen rings has resulted in rather slight | 15N coord | variations, not exceeding 10 ppm : 88.2 ppm for [Pd (4,4 - [15,16] The change of the whole heterocyclic ring system (but with the same type of coordination geometry) has been followed by more noticeable ca [10][11][12][13][14][15][16][17][18][19][20] [7,14] ; however, sometimes this effect can be also negligible: 98.5 ppm for trans-[Pd(isoquin) 2 Cl 2 ] versus 99.5 ppm for trans-[Pd(py) 2 Cl 2 ]. [7,19] The dependence on the electric charge of the complex is usually less than 10 ppm, as exemplified by the | 15N…”