1646-67-9Relevant academic research and scientific papers
Bis(imido)vanadium(V)-Catalyzed [2+2+1] Coupling of Alkynes and Azobenzenes Giving Multisubstituted Pyrroles
Kawakita, Kento,Beaumier, Evan P.,Kakiuchi, Yuya,Tsurugi, Hayato,Tonks, Ian A.,Mashima, Kazushi
supporting information, p. 4194 - 4198 (2019/02/26)
The combination of VCl3(THF)3 and N,N-bis(trimethylsilyl)aniline (1a) is an efficient catalyst for the [2+2+1] coupling reaction of alkynes and azobenzenes, giving multisubstituted pyrroles. A plausible reaction mechanism involves the generation of a mono(imido)vanadium(III) species as an initiation step, where 1a served as an imido source with concomitant release of 2 equiv of ClSiMe3, followed by a reaction with azobenzene to form a catalytically active bis(imido)vanadium(V) species via N=N bond cleavage.
Catalytic formal [2+2+1] synthesis of pyrroles from alkynes and diazenes via TiII/TiIV redox catalysis
Gilbert, Zachary W.,Hue, Ryan J.,Tonks, Ian A.
, p. 63 - 68 (2015/12/30)
Pyrroles are structurally important heterocycles. However, the synthesis of polysubstituted pyrroles is often challenging. Here, we report a multicomponent, Ti-catalysed formal [2+2+1] reaction of alkynes and diazenes for the oxidative synthesis of penta- and trisubstituted pyrroles: a nitrenoid analogue to classical Pauson-Khand-type syntheses of cyclopentenones. Given the scarcity of early transition-metal redox catalysis, preliminary mechanistic studies are presented. Initial stoichiometric and kinetic studies indicate that the mechanism of this reaction proceeds through a formally TiII/TiIV redox catalytic cycle, in which an azatitanacyclobutene intermediate, resulting from [2+2] alkyne + Ti imido coupling, undergoes a second alkyne insertion followed by reductive elimination to yield pyrrole and a TiII species. The key component for catalytic turnover is the reoxidation of the TiII species to a TiIV imido via the disproportionation of an η2-diazene-TiII complex.
TITANIUM (IV) COMPOUNDS AND METHODS OF FORMING HETEROCYCLIC COMPOUNDS USING SAME
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Paragraph 0094; 0095; 0096; 0097, (2016/08/17)
The present disclosure provides Titanium (IV) compounds and methods of making heterocyclic compounds such as pyrroles using Titanium (IV) compounds. In certain embodiments, the Titanium (IV) compound is present in catalytic amounts.
Palladium-catalyzed reaction of arylamine and diarylacetylene: Solvent-controlled construction of 2,3-diarylindoles and pentaarylpyrroles
Chen, Xiaopeng,Li, Xihui,Wang, Ningning,Jin, Jisong,Lu, Ping,Wang, Yanguang
scheme or table, p. 4380 - 4386 (2012/09/21)
By choosing DMF and dioxane as solvent, skeletons of indoles and pyrroles were constructed from alkynes and amines in the presence of PdCl2, respectively. These Pd-catalyzed reactions were phosphane-free with high atom efficiency and could be conducted under mild basic conditions. The proposed mechanism for the selective formation of indoles and pyrroles in different solvents is also discussed in this paper. Two different kinds of Pd-catalyzed cyclizations, leading to the construction of 2,3-diarylindole and pentaarylpyrrole from the same alkyne and aniline starting materials, were approached by choosing different solvents. The mechanisms for these solvent-controlled reactions are proposed and discussed. Copyright
Aggregation-induced emission enhancement of aryl-substituted pyrrole derivatives
Feng, Xiao,Tong, Bin,Shen, Jinbo,Shi, Jianbing,Han, Tianyu,Chen, Long,Zhi, Junge,Lu, Ping,Ma, Yuguang,Dong, Yuping
scheme or table, p. 16731 - 16736 (2011/05/06)
The relationship between the structures and light emission properties of five aryl-substituted pyrrole derivatives was studied during aggregation in THF-water mixtures. Only pentaphenylpyrrole clearly shows, however, an aggregation-induced emission enhanc
Reactions of cobaltacyclopentadiene complexes with organic azides directed toward synthesis of highly substituted pyrroles
Hong, Pangbu,Yamazaki, Hiroshi
, p. 133 - 142 (2007/10/02)
The reactions of the cobaltacyclopentadiene complexes (η5-C5H5)(PPH3)-Co(-CR1=CR2-CR3=CR4)- (I) with organic azides were investigated.The complex Ia (R1)=R2=R3=R4=Ph) reacts with phenyl azide at 80 degC to give 1,2,3,4,5-pentaphenylpyrrole in 73percent yeld.Similarly, the reactions of Ia with benzoyl and t-butoxycarbonyl azides give 1-benzoyl- and 1-(t-butoxycarbonyl)-2,3,4,5-tetraphenylpyrroles in 41 and 64percent yields, respectively, but reaction with p-toluenesulfonyl azide gives 2,3,4,5-tetraphenylpyrrole and 3,4,5,6-tetraphenylpyridazine in 35 and 45percent yields, respectively, in place of the expected 1-(p-toluenesulfonyl)-2,3,4,5-tetraphenylpyrrole.The reaction of Ic (R1=R4=Ph, R2=R3=CO2CH3) with phenyl azide at 130 degC gives 1,2,5-triphenyl-3,4-bis(methoxycarbonyl)pyrrole (IIc)and 2,5-diphenyl-3,4-bis(methoxcarbonylpyrrole (Vb) in 22 and 15percent yields, respectively.The reaction of Ic with benzenesulfonyl azide gives only Vb in 57percent yield.In the reaction of Id (R1=R3=Ph, R2=R4=CO2CH3) with benzenesulfonyl azide, Vb was unexpectedly obtained in 26percent yield, together with 2,4-diphenyl-3,5-bis(methoxycarbonyl)pyrrole (Vc, 30percent), which suggests that a skeletal rearrangement of the metallacycle IXd to IXc occurs during the reaction.The reaction of Ic or Id with benzoyl azide at 130 degC gives the 2(1H)-pyridinone derivatives VIIIa (82percent) and VIIIb (53percent), which are the products of the reaction of the corresponding cobaltacyclpentadiene with phenyl isocyanate generated by the rearrangement of benzoyl nitrene, in place of the expected, corresponding pyrrole.
FERRICYANIDE OXIDATION OF 1-SUBSTITUTED PENTAPHENYLPYRIDINIUM SALTS. A NOVEL ROUTE TO 1-SUBSTITUTED 2,3,4,5-TETRAPHENYLPYRROLES
Boehm, Stanislav,Slavik, Hanus,Kuthan, Josef
, p. 200 - 205 (2007/10/02)
Oxidation of 1-substituted 2,3,4,5,6-pentaphenylpyridinium salts Ia-Ij by potassium ferricyanide in an alkaline medium yields the corresponding 1-substituted 2,3,4,5-tetraphenylpyrroles in 68 to 76percent yields.The selectivity of the reaction is discusse
A CHEMICAL AND THERMOCHEMICAL STUDY OF NON-OBSERVED SYMMETRY ALLOWED REACTIONS
Ranganathan, S.,Ranganathan, D.,Ramachandran, P. V.,Mahanty, M. K.,Bamezai, S.
, p. 4171 - 4184 (2007/10/02)
A variety of reactions, whilst predicted to be symmetry allowed, are not observed experimentally.Several such non-observed yet allowed reactions have been studied in order to understand them and to possibly bring about, with suitably modified substrates, their observation.For example, although ozone adds to ?-bonds, the isoelectronic nitro group does not, due to a high activation energy barrier.This reaction is of the type ABC.Molecular orbital calculations of a series of 1,3-dipolar species reveal a correlation of the ? bond order with their effectiveness in -additions.Based on this, the nitro group as well as ozone should be considered as poor dipolar agents.The exceptionally high ΔHof of ozone (+34.00 kcal mol-1) as compared with that of nitrobenzene (+3.8 kcal mol-1) could possibly explain the reactivity of the former.This is reflected in an estimated ΔHo value of -45.5 kcal mol-1 for the ethylene-ozone addition as compared with +7.5 kcal mol-1 for the non-occuring ethylene-nitrobenzene addition.Thermochemical calculations demonstrate that the nitrogroup is more prone to undergo addion as a 2? partner than as a 1,3-dipolar reagent.The thermal, nitro group-olefin addition has been examined using a variety of electrophilic nitrobenzenes with tetracyclone as the common substrate.The extent of cyclo-addition was assessed on the basis of the isolation of 2-benzoyl-3,4,5-triphenylfuran. 4-Nitro-4'-methyl diphenyl sulfone and 4,4'-dinitro diphenyl sulfone have been identified as efficient reagents for these reactions.The former compound has been found to add to even non-conjugated olefins.The clean thermal transformation of crystalline 7,7-dimethyl-bicycloheptane-1-nitrile oxide to the corresponding isocyanate is an example of the observable ABC change.In this case, the oxazirine corresponding to B, arising from conrotatory cyclisation, undergoes irreversible rupture (BC).Such transformations are not observed with the stereochemically more favoured nitrones since these belong to the type AB.The ?4s+?2s addition of carboxylates to olefins would lead to a carbon base at the expense of an oxygen one.This is clearly unfavourable and is not observed.On the other hand, the reverse of this reaction, namely , the fragmentation of ketal conjugate bases to carboxylates would be expected to be facile.This is indeed so and the process has been shown to be concerted.Ketals from p-nitrobenzaldehyde are shown to undergo fragmentation with 1,5-diazabicyclononene-5 (DBN) to olefins.The carboxylate-olefin addition belongs to the general category ?+A-B-, that encompasses cycloadditions, electrocyclic reactions and sigmatropic shifts.An equation ΔG deg=BHa-pKAHa)+X>kcal mol-1, wherein X is dependent on the reaction type has been derived for predicting the ΔGo for these ?+AB processes.Of practical interest is the development of perturbed ?+A1B1 systems that are predicted to occur in the forward direction, where the parent type ...
