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N-Heterocycles
Published in Navjeet Kaur, Metals and Non-Metals, 2020
Another study by Kaneta et al. [210] reported alkyne co-trimerization reactions for the synthesis of isoindoline in moderate yields using Mortreux’s catalyst system derived from p-chlorophenol and Mo(CO)6. Mono-alkynes possessing o-hydroxyphenyl group provided trimerized products, while alkynes bearing m- or p-hydroxyphenyl group resulted in cross-alkyne metathesis products under these conditions. Under similar reaction conditions, the diyne underwent co-trimerization with many mono-alkynes to provide the cyclized product along with the by-product (Scheme 80) [211]. The isolation of the by-product indicated that this catalytic reaction occurred using molybdenacyclopentadiene complex. The yields of desired trimerized products improved when 15 eq. of monoalkyne was used. Absolute intramolecular [2+2+2]-cyclization reactions were also performed using similar catalyst systems [212].
Major Classes of Conjugated Polymers and Synthetic Strategies
Published in Sam-Shajing Sun, Larry R. Dalton, Introduction to Organic Electronic and Optoelectronic Materials and Devices, 2016
Bunz et al. optimized the reaction conditions of the alkyne metathesis utilizing Mo(CO)6 and 4-chlorophenol by increasing the reaction temperature from 105°C to 130°C–150°C (see Scheme 6.25). And the reaction was performed with a purge of nitrogen to remove the formed 2-butyne. By this method, they obtained a polymer with a degree of polymerization of 180 (GPC). It was indicated that this reaction is competitive to the Pd-catalyzed coupling reaction.
A thiophenic alkynylplatinum(II) terpyridyl complex: synthesis and photophysical properties
Published in Journal of Coordination Chemistry, 2022
Peng Xu, Xi Qin, Huiyuan Duan, Huafeng Chen, Lei Zhai, Yanjie Qin, Xin Liu, Yulan Zuo, Shuchen Pei, Xin Lian, Huan Yi, Xiaodong Su, Jinling Zhang
The synthesis of 3 commenced with the preparation of the iodobenzene derivative 4 (Scheme 3), which was easily synthesized according to the route developed in our previous work [18]. Iodobenzene 4 was transformed into triyne 5 by Sonogashira cross coupling with triisopropylsilylacetylene (TIPSA) in acceptable yield. Subsequently, through reaction with excess sodium hydride (NaH) in toluene, the two hydroxyisopropyl groups in triyne 5 were removed in one pot, thus affording di-terminal alkyne 6 in excellent yield. Furthermore, the Sonogashira coupling of di-terminal alkyne 6 with 2-fold 2-iodo-5-methylthiophene proceeded smoothly to afford triyne thiophene 7 in moderate yield. Then, the triyne thiophene 7 was converted into the corresponding terminal alkynyl 8 in excellent yield by treatment with tetrabutylammonium fluoride (TBAF). Finally, followed by the similar CuI catalyzed chloride-to-alkyne metathesis for those related alkynylplatinum(II) terpyridyl complexes [19], the preparation of 3 was achieved in good yield through ligand exchange of terminal alkynyl 8 with [Pt(tpy)Cl](PF6).
Reactivity of titanium imidazolin-2-iminato complexes with 2,6-diisopropylaniline and 2-{(2,6-diisopropylphenyl)-iminomethyl}pyrrole
Published in Journal of Coordination Chemistry, 2018
Kishor Naktode, Suman Das, Hari Pada Nayek, Tarun K. Panda
Organo-imido complexes of transition metals have been researched widely because of their significance in numerous biological, industrial, and catalytic processes [1]. Researchers’ interest is evoked mainly by the ability of the metal-imido group (M = NR) to undergo a wide range of organic transformations, such as metathesis, cycloaddition, C–H bond activation, and hydroamination reactions [2–4]. In addition, imido ligands are frequently used as efficient ancillary ligands in organo-transition metal chemistry, for example, in olefin metathesis, and as polymerization catalysts [5–8]. Monoanionic imidazolin-2-iminato ligands, such as ImRN– (1), are often described by the two limiting resonance structures, 1A and 1B (Scheme 1), showing that the capacity of the imidazolium ring to stabilize a positive charge results in highly basic ligands [9] with strong electron-donating capacity toward early transition metals [10–13]. Since they are capable of donating 2σ and 4π-electrons, these ligands can be considered monodentate analogs of cyclopentadienyls, C5R5, as well as monoanionic imido ligands, similar to those described for related phosphoraneiminato ligands [14]. Tamm et al. were able to effectively apply this concept to introduce imidazolin-2-iminato ligands into transition metal, lanthanide, and recently, actinide metal chemistry, to accomplish very short M–N bonds. This led to further research into the multiple bonding characters between M–N bonds [15–33], which possess multiple bonding characters, as their reactivity is very similar that of M = N imido bonds [34]. Currently, various metal complexes supported by imidazolin-2-iminato ligands exhibit high activity in ethylene (co)polymerization and alkyne metathesis [10,12,21,35–47].