Sonogashira-Hagihara Cross-coupling Reaction Research Articles

Protonation-induced Cyclization of 1,8-Bis(arylethynyl)anthraquinones: Monopyrylium Salt Formation and Intensification of Donor–Acceptor Interaction

Abstract We previously reported protonation-induced double cyclization reaction of 1,4-Ar2Aq and 1,5-Ar2Aq (Ar2Aq: bis(arylethynyl)anthraquinone) with strong acid HX that generated the corresponding dipyrylium salts [1,4-Ar2Pyl2]X2 and [1,5-Ar2Pyl2]X2. In this communication we disclose the protonation reactions of 1,8-Fc2Aq (Fc: ferrocenyl), 1,8-Am2Aq (Am: 4-N,N-bis(4-methoxyphenyl)aminophenyl), and 1,8-AmFcAq, which is the first example of heterodonor molecules in the Ar2Aq series, and synthesized by means of stepwise Sonogashira–Hagihara cross-coupling reactions. In contrast to the 1,4-Ar2Aq and 1,5-Ar2Aq series, 1,8-Ar2Aq undergoes protonation-induced single cyclization, so that it is converted into the corresponding monopyrylium salt [1,8-Ar2Pyl]X. [1,8-Ar2Pyl]X features an extremely small HOMO–LUMO gap (0.50–0.73 V), ascribable to the significant lowering of the LUMO level upon the pyrylium formation.

C,C-Diacetylenic phosphaalkenes in palladium-catalyzed cross-coupling reactions

The reactivity of bis-TMS-substituted C,C-diacetylenic phosphaalkene (A(2)PA) 1 in Sonogashira-Hagihara cross-coupling reactions has been examined. The selective and successive deprotection of the two silyl groups in 1 is enabled by the steric bulk of the Mes* group which renders the acetylene trans to Mes* more reactive and thereby facilitates selective and consecutive couplings with iodoarenes. In situ transformation of the TMS-protected acetylenes into Cu(i)acetylides is the key step in the synthetic sequence and enables the preparation of the first dimeric A(2)PA linked by a phenylene spacer. cis-trans Isomerization across the P[double bond, length as m-dash]C bond is triggered by a tertiary amine and exclusively observed in the case of nitrophenyl-substituted A(2)PAs. The introduced aryl groups are integral parts of the entire π-system as evidenced by spectroscopic and electrochemical studies.

Synthesis of Maleimide-Functionalized Water-Soluble Poly(arylene ethynylene)s

We have synthesized water-soluble poly(arylene ethynylene)s having maleimide groups capable of reacting with thiol-containing biomolecules. The number-average molecular weights of the polymers range from 11,000 to 14,000. The polymerization was carried out by palladium-catalyzed Sonogashira-Hagihara cross-coupling reaction with good yield. The polymers showed blue emission colors in their methanol solutions, while green color was observed in aqueous solutions with decreased emission intensity.

Silver(I) Coordination Polymers Based on A Nano-Sized Bent Bis(3-acetylenylphenyl-(4-cyanophenyl))oxadiazole Ligand: The Role of Ligand Isomerism and the Templating Effect of Polyatomic Anions and Solvent Intermediates

One nanosized oxadiazole bridging ligand, bis(3-acetylenylphenyl-(4-cyanophenyl))oxadiazole (L11), was designed and synthesized by the reaction of bis(3-iodophenyl)oxadiazole with 4-cyanophenylacetylene via a Sonogashira-Hagihara cross-coupling reaction. Eight Ag(I)-L11 coordination polymers with one-, two-, or three-dimensional structures have been successfully prepared by the reaction of L11 with various Ag(I) salts in solution. New coordination polymers were fully characterized by infrared spectroscopy, elemental analysis, and single-crystal X-ray diffraction. All new complexes contain silver heteroatom cluster-connecting nodes, and the L11 ligand is "doubling up" in the frameworks. In this Ag(I)-L11 system, the conformation of L11 is versatile because of the conformational rotation around the central oxadiazole moiety and depends greatly on the counterion and solvent system used in the formation of the complexes. In addition, the luminescence property and host-guest chemistry of some complexes were investigated primarily.