Rare direct imidation of aromatic metallacycle by reaction of CpCo(dithiolene) complex with N-halosuccinimide

The aromatic [CpCo(S₂C₂(R)(H))] (R = Ph, Me, 9-phenanthryl, H) complexes reacted with N-halosuccinimides (NXS; X = Cl, Br, I) in carbon tetrachloride at room temperature to undergo the N-succinimide substitution reaction on the dithiolene ring, but no halogenated dithiolene complex was obtained. The imidation products [CpCo(S₂C₂(R)(N-sccinimide))] were yielded up to 64% where X = I and R = 9-phenanthryl. The reaction of [CpCo(S₂C₂(Ph)(H))] with N-bromophthalimide (NBP) also gave the imidation product [CpCo(S₂C₂(Ph)(N-phthalimide))]. This is the rare direct imidation reaction to an aromatic metallacycle by NXS. The reaction of [CpCo(S₂C₂H₂)] (R = H) with NIS afforded the double imidation product. One by-product in this reaction was the dithiolene-dithiolene homo-coupling product [CpCo(S₂C₂(R))]₂ (R = Ph, Me, 9-phenanthryl). The microwave-enhanced (MW) reactions were attempted in the carbon tetrachloride solution. Although the solution temperature increased up to only 43 °C by MW irradiation, the imidation reaction worked with short reaction time.     

Regioregular head‐to‐tail poly(6‐alkylpyridine‐2,5‐diyl)s and a new type of packing structure of the polymer in the solid state

New regioregular head‐to‐tail type poly(6‐alkylpyridine‐2,5‐diyl)s (P6RPys; R = nonyl, dodecyl, and pentadecyl) were prepared by organometallic polycondensation. The head‐to‐tail (HT) content in the polymers was higher than 95%, as revealed by ¹H NMR spectroscopy. Powder X‐ray diffraction data of HT‐P6RPys indicated that P6RPys formed a new type of structure composed of an alternating end‐to‐end packed unit and an interdigitation packed unit. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 215–222, 2005     

Control of thermoresponsive property of urea end‐functionalized poly(N‐isopropylacrylamide) based on the hydrogen bond‐assisted self‐assembly in water

The precise synthesis and variation in the thermoresponsive property based on the supramolecular assembly of a novel urea end‐functionalized poly(N‐isopropylacrylamide) (PNIPAM) were studied. A series of PNIPAMs with different diphenylurea groups at the chain end (X? Ph? NH? CO? NH? Ph? trz? PNIPAM: X = H, OCH₃, CH₃, NO₂, Cl, and CF₃) were synthesized by using a combination of the atom transfer radical polymerization and the copper(I)‐catalyzed azide‐alkyne cycloaddition. The cloud point of the obtained polymers depended on the hydrogen‐bonding ability of the introduced urea group. The ¹H NMR measurement suggested that the obtained PNIPAM assembled in water via the intermolecular hydrogen bonding by the terminal urea group. From the dynamic light scattering and transmission electron microscopy measurements, the aggregated nanoparticles of the resulting polymer were directly observed in water at a temperature below its cloud point. The hydrogen‐bonding property of the chain end urea group was concluded to be involved in the aggregation of the PNIPAM in water, leading to the variation in its cloud point. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 6259–6268, 2009     

Cage Effects in Dimethylaminyl Radical Formation

The rate of decomposition of 1,1,4,4-tetramethyl-2-tetrazene (TMT) was measured in various unbranched alkanes of varying viscosities. The observed rate constant for the decomposition of TMT decreases with the viscosity of the solvent. A compensating change was found in the enthalpy and entropy of activation. It was also found that the decomposition of TMT occurs by the scission of only one N-N single bond and undergoes cage return in the alkanes by recombination of radicals.     

Hetero-Type Benzannulation Leading to Substituted Benzothio-Phenes

TiCl₄ (or SnCl₄)-promoted hetero-type benzannulation reactions using various (2,2-dichlorocyclopropyl)(thiophen-2-yl)methanols proceeded smoothly to produce uniquely substituted 4-chlorobenzothiophenes (five examples). The present approach involves the first distinctive thiophene formation from thiophene cores, in contrast to traditional methods of thiophene formation from benzene cores. The stereocongested (less reactive) Cl position in the obtained 4-chlorobenzothiophenes functioned successfully as the partners of three cross-coupling reactions: (i) a Suzuki–Miyaura cross-couplings using Pd(OAc)₂/SPhos/K₃PO₄ catalysis (seven examples; 63–91%), (ii) a hydroxylation using KOH/Pd(dba)₂/tBu-XPhos catalysis (85%), and (iii) a borylation using a B₂(pin)₂/Pd(dba)₂/XPhos/NaOAc catalysis-provided 4-(pin)B-benzothiophene (58%).