The conversion of azobenzenes to phenazines: A new molecular rearrangement

When azobenzenes arc heated with ferrous oxalate or with a fused mixture of aluminum chloride and sodium chloride the corresponding phenazines are formed in low yield. Azobenzene itself is exceptional in giving benz[c]cinnoline with AlCl₃-NaCl. Azoxybenzenes and ferrous oxalate give azobenzenes and some phenazines, while azoxybenzene itself also gives 2-hydroxyazobenzene via a Wallach-type rearrangement. The rearrangements are thought to occur at the surfaces of the reagent. No rearrangement to the phenazines occurs in the absence of the reagent.     

Synthesis of 9-alkylidene-9H-fluorenes by a novel palladium-catalyzed rearrangement

In the presence of a palladium catalyst and NaOAc, aryl iodides react with 1-aryl-1-alkynes to afford 9-alkylidene-9H-fluorenes in good yields. This process appears to involve (1) oxidative addition of the aryl iodide to Pd(0), (2) alkyne insertion, (3) rearrangement of the resulting vinylic palladium intermediate to an arylpalladium species, and (4) aryl-aryl coupling with simultaneous regeneration of the Pd(0) catalyst.     

Synthesis of polyisocyanurates by thermal rearrangement of polycyanurates

Polyisocyanurates have been successfully prepared by the thermal rearrangement of polycyanurates, which were obtained from 2,4‐dichloro‐6‐methoxy‐1,3,5‐triazine and bisphenol monomers. The thermal rearrangement was carried out in the presence of a small amount of tetrabutylammonium bromide (TBAB) as a catalyst at 200 °C for 30 or 60 min in an argon atmosphere, and the degree of arrangement was greater than 95%. Transparent and amorphous polyisocyanurate films were obtained and showed a good thermal stability with a 5% weight loss temperature above 340 °C in nitrogen and the glass transition temperature above 210 °C. Films with a 10‐µm thickness exhibited an excellent transparency above 90% at 400 nm. Furthermore, the thermal rearrangement of 2,6‐bis(4‐methoxyphenyl)‐6‐methoxy‐1,3,5‐triazine to 1,3‐bis(4‐methoxyphenyl)‐5‐methyl‐1,3,5‐triazinane‐2,4,6‐trione was investigated in detail. It was found that the complete thermal rearrangement was successfully accomplished in the presence of 2 wt % TBAB at 150 °C for 20 min in an argon atmosphere. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 692–698     

Synthesis of (R)-2-(benzyloxy)-tetrahydro-5,5-dimethylfuran by a new oxidative rearrangement

The rearrangement under oxidative conditions of 3-(benzyloxy)-tetrahydro- 2,6,6-trimethyl-2H-pyran-2-carbaldehydes to afford a chiral protected tetrahydrofuran lactol is described.     

Diisobutylaluminium hydride (DIBAL-H) as a molecular scalpel: a new mechanistic proposal for a spiroketal rearrangement

Taking advantage of our knowledge of the capacity of DIBAL-H to de-O-alkylate, we propose an alternative mechanism for a spiroketal rearrangement described by E. Suàrez. We also show that this proposal can account for the formation of the secondary product, whose original structure we propose to correct.     

Aza-Ferrier rearrangement of glycals with amides promoted by molecular iodine

Amidoglycosidation of tri-O-acetyl-d-glucal with different N-nucleophiles such as t-butyl carbamate, N-benzyl carbamate, N-ethyl carbamate, tosyl amide, and mesyl amide has been achieved using an equimolar amount of molecular iodine under mild and neutral conditions to afford the corresponding N-glycosyl amides in good yields with a preferential α-anomeric selectivity. The use of iodine makes this method simple, convenient, and cost-effective. This is the first report on aza-Ferrier rearrangement using molecular iodine.     

Synthesis of TS-1 molecular sieves using a new Ti source

The incorporation of Ti in the MFI structure using a cheap and easy to handle source, the hexafluorotitanic acid, was successfully achieved without the formation of contaminant phases. The TS-1 samples with 1%, 2%, and 2.5% Ti present a linear increase in the cell parameters. This indicates that the Ti present in the solid is incorporated into the framework, and this is confirmed by infrared analysis. The TS-1 particles present morphology that is typical of the MFI structure. The UV-vis diffuse reflectance results indicate the existence of tetra- and hexacoordinated framework Ti species. Independent of Ti content, all of the samples present similar activity for the oxidation of cyclohexene using hydrogen peroxide as an oxidant agent. Also, a high selectivity for the formation of the corresponding epoxide is observed.     

Synthesis and biomimetic rearrangement of a chiral diterpene dioxide

As pan of a biomimetic approach towards me marine triterpene teurilene (2), the synthesis of the chiral diepoxide 3 is described. Aiming at the synthesis of the squalene tetraepoxide 1, double Sharpless epoxidation led to the intermediate bisglycidic alcohol 7 being subject to a stereochemical analysis.     

Synthesis of substituted naphthalenes via a catalytic ring-expansion rearrangement

A new methodology for the preparation of substituted naphthalenes starting from readily available indenones, organometal reagents, and trimethylsilyldiazomethane via a catalytic rearrangement process is described. Hindered biaryl naphthalenes, including triortho-substituted biaryls, can be accessed through our method. Our results are consistent with a mechanism involving a benzobenzvalene intermediate.     

Synthesis and rearrangement of triazinoquinazolines

Selective syntheses of triazino[4,3-a]quinazolines 3a–e and their isomeric triazino[3,2-b]quinazolines 4a–e by cyclization of the appropriate α -keto acid hydrazones 2a–e under different reaction conditions are described. The angular triazinoquinazolines 3a–e were readily rearranged to the corresponding linear isomers 4a–e when heated in acetic anhydride in the presence of sodium acetate. This rearrangement was proposed to proceed via the intermediate isomeric triazino[3,4-b]quinazolines 5a–e . The N-methyl derivative 10 (of the intermediate 5b ) was prepared and rearranged to 11 , which is the N-methyl derivative of 4b .     

Synthesis of lupiwighteone via a para-Claisen-Cope rearrangement

The lanthanide catalysed para-Claisen-Cope rearrangement has been used as the key step in a short synthesis of the prenylated isoflavone, lupiwighteone. The Mitsunobu reaction was employed for the 5-O-prenylation of the acid/base sensitive acetylated isoflavone to afford the allyl aryl ether precursor, which was then rearranged under mild conditions in good yield. Rearrangement of the isoflavone gave the 8-prenylisoflavone as a single product, in good yield.     

Synthesis of cyclophellitol utilizing a palladium chloride mediated-Ferrier-II rearrangement

Cyclophellitol and its C3-epimer have been synthesized from5-enoglucopyranoside and 5-enomannopyranoside, respectively. The carbocyclic skeletonwas constructed through a Ferrier-II reaction meditated by PdCl2.     

Synthesis and thermal rearrangement of a potential butalene-anthracene adduct

The synthesis of propellane $\text{4}$, a formal Diels-Alder adduct of 1,4-dehydrobenzene and anthracene, is reported. This material does not undergo a retro-Diels Alder reaction on pyrolysis, but instead rearranges to benzofluoranthene $\text{5}$.     

新型磷酸硅铝分子筛SAPO-53的合成与表征

以氢氧化已烷双铵(R(OH)2)为模板剂,采用水热条件合成了高结晶度的SAPO-53分子筛。并采用XRD、SEMEDX、FT-IR、MAS NMR、电泳仪、N2吸附-脱附、TG-DTG等手段对合成的分子筛进行表征。考察了硅铝比、磷铝比、模板剂的用量以及晶化时间等条件对合成SAPO-53分子筛的作用。29Si MAS NMR表明,Si主要以四配位形式进入了AlPO4-53的骨架中,SAPO-53相对结晶度先增加后开始缓慢下降,Zeta电位值先增加后保持不变,与以甲胺为模板剂合成相比,氢氧化已烷双铵的用量比甲胺减少了一半,同时缩短了晶化时间,降低了合成的难度。通过计算得到SAPO-53的表观生长速率大于成核速率,说明成核过程是速率控制步骤。     

Synthesis of novel types of divalent saccharide structures by a ketene acetal Claisen rearrangement

A simple allyl uronate was rearranged to give the branched product, which in turn could be transformed into a spiro-annellated bicyclic compound. More complex allyl uronates of d-and l-arabinose were rearranged to give novel methylene-bridged dimeric saccharide structures.