A new route to phosphonium polymer network solids via cyclotrimerization

An organo‐main group network solid having tetrahedral phosphonium vertices was prepared from a diacetyl monomer via a straightforward cyclotrimerization reaction. The network solid composition was examined by FT‐IR spectroscopy and elemental microanalysis, revealing quantitative reaction of carbonyl moieties and a 67% degree of cross‐linking. The reaction yielded a material having a layered structure that is comprised of an amorphous polymer and which is thermally stable up to 370 °C in air with a char yield of 40% upon heating as high as 800 °C under N₂. The polymer is stable to 6 M NaOH(aq ) at 60 °C for 24 h and takes up only 10.63% of water by mass at room temperature. The surface morphology, as examined by AFM, revealed a very smooth as‐prepared film (RMS roughness of 3 nm). The specific surface area measured by BET analysis with N₂ gas is 9 m² g^?1, indicating a type II, nonporous material. Physisorption with CO₂ revealed that the phosphonium network solid has additional affinity for CO₂, suggesting that such materials may have use for applications such as CO₂ capture. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55 , 1620–1625     

A highly practical instant catalyst for cyclotrimerization of alkynes to substituted benzenes

[reaction: see text] A 2-(2,6-diisopropylphenyl)iminomethylpyridine (1a)/CoCl(2).6H(2)O/Zn reagent has been developed as an effective instant catalyst for the intra- and intermolecular cyclotrimerization of alkynes to substituted benzenes, making the method extremely practical since the reagent, 1a/CoCl(2).6H(2)O/Zn, is inexpensive and easy to handle and the reaction is less sensitive to moisture and is reasonably general.     

Equilibrium cyclotrimerization of n-butyraldehyde

n-Butyraldehyde was cyclotrimerized by using boron trifluoride etherate as an initiator at ?10 to 25°C under various conditions, e.g., in methylene chloride, in toluene, and without adding solvent. An equilibrium between the monomer and its cyclic trimer was observed, the equilibrium constant being highly dependent on not only the reaction temperature and the kind of solvents, but also the initial monomer concentration. A consistent interpretation for the results was obtained by the thermodynamic treatment of the equilibrium system as a nonideal solution composed of the monomer, its cyclic trimer, and solvent, in consideration of the intermolecular interactions between any two components.     

Iron-catalyzed intramolecular cyclotrimerization of triynes to annulated benzenes

An iron species derived from FeCl₂ or FeCl₃ by in situ reduction with zinc powder in the presence of imidazol-2-ylidene or bidentate nitrogen ligand could effectively catalyze intramolecular cycloisomerization of triynes to annulated benzenes. With a 2-iminomethylpyridine ligand, hydrates of FeCl₂ and FeCl₃ as well as their anhydrous ones could be used.     

A novel route to meta-aminobenzotrifluoride

Product patterns can be altered in reactions of $\text{m}$-nitrobenzotrichloride [VI] with [AHF]_x·NH₄F complex. Side-chain fluorination predominates under ‘mild’ conditions. In contrast. ‘forcing’ conditions affected unexpected $\text{in}$-$\text{situ}$ fluorination-reduction to give $\text{m}$-aminobenzotrifluoride [V] in high yield [75%] and purity [99.6%]. $\text{in}$-$\text{situ}$ reduction is probably initiated by a combination of iron from the stainless steel autoclave and trace amounts of moisture. The transformation of [VI] to [V] represents another type of $\text{in}$-$\text{situ}$ fluorination-reduction nitroaromatics, e.g. nitrobenzene [VII] to $\text{p}$-fluoroaniline [VIII]. $\text{o}$-Nitrobenzotrichloride [XI] degraded under ‘forcing’ conditions with [AHF]_x·NH₄F.     

A new route to spirooxindoles

[reaction: see text]Reaction of indole amides 5 with tributylstannane gave spiroindolenines 9 which are readily converted into spiropyrrolidinyloxindoles. This tricyclic system is found in a number of interesting natural products.     

A synthetic route to thionolactones

The treatment of O-alkyllactonium tetrafluoroborate salts with anh. NaSH in CH₃CN at 0°C led to five-, six-, and seven-membered thionolactones (44– 90% yield).     

A Mitsunobu route to C-glycosides

C-Glycosides were successfully prepared via dehydrative alkylation under Mitsunobu conditions, using substituted sulfonyl methanes as nucleophiles. The materials prepared were converted to useful C-glycoside intermediates. An application of this approach toward the synthesis of C-glycolipids is presented.     

A new route to alkenylcyclobutenes

Reaction of titanium cyclobutylidene complexes, prepared by the desulfurizative titanation of 1,1-bis(phenylthio)cyclobutanes with Cp₂Ti[P(OEt)₃]₂, with alkynes gave 1-(alk-1-enyl)cyclobutenes.     

A convenient route to heteronaphthacenes

Heteronaphthacenes 1 were prepared in two steps from 1,3-dihydrobenzo[c]thiophene 2,2-dioxide ( 4 ) and dienophiles 2 via convenient high-temperature Diels-Alder reactions.     

A versatile route to benzocanthinones

Benzocanthinone (1) and five analogs (10, 12-15) were prepared by radical-induced cyclizations of halo N-aroyl derivatives of β-carboline and carbazole.     

A nickel-catalyzed route to pyridines

A mild and general route for preparing pyridines from nitriles and diynes is described. Ni/imidazolyidene complexes were used to mediate cyclization alkynes and both aryl and alkyl nitriles at ambient temperature. In addition, the efficacy of this protocol allows for the preparation of a fused seven-membered pyridone and for intermolecular cyclizations. When an asymmetrical diyne was employed, cyclization afforded a single pyridine regioisomer.     

A straightforward route to spiroketals

A straightforward route to 1,7-dioxa-, 1,4,7-trioxa- and 1,4,7,10-tetraoxaspiro[5.5]undecanes, starting from commercially available 3-chloro-2(chloromethyl)prop-1-ene, is described.