Palladium-Mediated Functionalization of Heteroaromatic Cations:  Comparative Study on Quinolizinium Cations

Abstract

An efficient palladium-catalyzed cross-coupling reaction on heteroaromatic cations is described. A comparative study of the Stille and Suzuki reactions shows that only the Stille reaction is able to produce an efficient C-C bond formation between any of the four isomeric bromoquinolizinium bromides and a variety of stannanes. In the presence of the catalysts Pd(PPh3)4 or Pd2(dba)3P(o-Tol)3, vinyl, ethynyl, aryl, and heteroaryl groups are successfully incorporated into the quinolizinium system in satisfactory yields under mild reaction conditions. This procedure represents a marked improvement on the functionalization of this class of heteroaromatic cation.

Bis[tri(o-tolyl)phosphine]palladium

“…54 For example, the combination of Pd 2 dba 3 and P(o-tolyl) 3 has been used to couple 2-bromoquinolizium bromide and tributylphenylstannane to give the arylated product in 60% yield. 55 A similar yield was found when PPh 3 was used instead of P(o-tolyl) 3 . The arylated product could also be obtained in 47% yield by using PhB(OH) 2 in a Suzuki reaction (Scheme 4).…”

Nonlinear Emission of Quinolizinium-Based Dyes with Application in Fluorescence Lifetime Imaging

“…MOP3 was obtained by the Sonogashira reaction as previously reported . The Heck reaction on 2-vinyl quinolizinium hexafluorophosphate allowed for the preparation of compounds MOP2 and DMA2 with acceptable yields. − Finally, quadrupolar V-shape chromophores represented by disubstituted quinolizinium derivatives V-MOP2 and V-DMA2 were both obtained from 2,8-dimethylquinolizinium bromide by a double Knoevenagel condensation under the same conditions used for the synthesis of the dipolar compounds and following the procedure reported earlier. ,, A more detailed description of materials, instrumentation, and synthetic procedure as well the NMR spectra of the new compounds ( MOP1 , MOP2 , DMA1 and DMA2 ) can be found in the Supporting Information (S1–S5).…”

Molecular Assembly of Alkylated Fused Expanded Pyridinium for a Highly Conductive Anion-Exchange Membrane

“…To incorporate FEP units into the polymer side chain, Br–C x FEP was converted to ethynylated C x FEP (ethynyl-C x FEP) via Migita–Kosugi–Stille coupling. , The obtained ethynyl-C x FEP was incorporated into base polymers with azide groups in the side chain via copper-catalyzed alkyne–azide cycloaddition (CuAAC) (Scheme ). − In this study, base polymers (azide n -BMA m : n , m are copolymerization ratios) were synthesized by the free-radical polymerization of 12-azido-1-dodecanoyl methacrylate and n -butyl methacrylate (BMA) in a certain copolymerization ratio using azobis­(isobutyronitrile) (AIBN) as an initiator .…”