Pyrrole Syntheses Based on Titanium‐Catalyzed Hydroamination of Diynes.

Ramanathan, Balasubramanian; Keith, Adam J.; Armstrong, Douglas L.; Odom, Aaron L.

doi:10.1002/chin.200450071

Cited by 3 publications

(4 citation statements)

References 2 publications

(1 reference statement)

Supporting

Mentioning

Contrasting

Order By: Relevance

mentioning

confidence: 99%

“…The [2 + 2] cycloaddition reaction forms the basis of a range of useful catalytic transformations for early metal imido complexes, including alkyne carboamination, 4,5 alkyne hydroamination, 6,7 and the assembly of pyrroles from alkynes and amines. 7,8 Despite this utility, these catalysts often have limited substrate scope, which may be partly related to the Lewis acidity of the early transition metal. For example, catalytic pyrrole formation by Ti-catalyzed [2 + 2 + 1] reactions fail for alkynyl esters and tethered alkyl ethers, likely due to the oxygen donors blocking access to the oxophilic metal.…”

mentioning

confidence: 99%

See 1 more Smart Citation

Catalytic Carbodiimide Guanylation by a Nucleophilic, High Spin Iron(II) Imido Complex

et al. 2021

View full text Add to dashboard Cite

Reduction of the three-coordinate iron(III) imido [Ph 2 B( t BuIm) 2 FeNDipp] (1) affords [Ph 2 B( t BuIm) 2 Fe NDipp][K(18-C-6)THF 2 ] (2), a rare example of a high-spin (S = 2) iron(II) imido complex. Unusually for a late metal imido complex, the imido ligand in 2 has nucleophilic character, as demonstrated by the reaction with DippNH 2 , which establishes an equilibrium with the bis(anilido) complex [Ph 2 B( t BuIm) 2 Fe(NHDipp) 2 ][K(18-C-6)THF 2 ] (3). In an unusual transformation, formal insertion of i PrNCN i Pr into the FeN(imido) bond yields the guanidinate [Ph 2 B( t BuIm) 2 Fe( i PrN) 2 CNDipp][K(18-C-6)THF 2 ] (4). Reaction of 4 with excess DippNH 2 provides 3, along with the guanidine ( i PrNH) 2 CNDipp. As suggested by these stoichiometric reactions, 2 is an efficient catalyst for the guanylation of carbodiimides, converting a wide range of aniline substrates under mild conditions.

show abstract

mentioning

confidence: 99%

mentioning

confidence: 99%

Catalytic Carbodiimide Guanylation by a Nucleophilic, High Spin Iron(II) Imido Complex

et al. 2021

View full text Add to dashboard Cite

show abstract

“…1,6-Diphenylhexa-1,5diyne (2a). 27 Purified by column chromatography (Hex); white solid (26.6 mg, 77%); mp 54−56 °C; 1 H NMR (600 MHz, CDCl 3 ) δ 7.43−7.40 (m, 4H), 7.30−7.27 (m, 6H), 2.73 (s, 4H); 13 C{ 1 H} NMR (151 MHz, CDCl 3 ) δ 131.9, 128.4, 128.0, 123.8, 88.6, 81.8, 20.0; IR (neat) ν max = 2925, 2851, 2360 cm −1 ; R f 0.29 (Hex).…”

Section: Synthesis Of 15-diynes (2a−2s)mentioning

confidence: 99%

Photoredox Selective Homocoupling of Propargyl Bromides

2022

View full text Add to dashboard Cite

Since the alkynyl moiety is one of the most versatile synthons for many other functional groups, 1,5-diynes (Wurtztype products of propargyl halides) would be valuable synthetic building blocks for the synthesis of complex functional molecules. However, despite the high and similar reactivity of propargyl radicals compared to allyl and benzyl derivative radicals, a photoredox Wurtz-type reaction of propargyl halides has not yet been developed. In this study, we developed the visible-light-induced selective homocoupling of propargyl bromides to form 1,5-diynes. Electrochemical and photophysical experiments showed that the key propargyl radical generation involves a reductive quenching cycle of the photoexcited [Ir(III)]* photocatalyst in the presence of N,N-dicyclohexylmethylamine. The product 1,5-diyne underwent one-step conversion to the functionalized indole derivative via Rhcatalyzed coupling with N-phenylacetamide. These results indicated the high utility of the developed homocoupling method.

show abstract

“…Figure 3 shows some examples involving 1,4-diynes. 24 Concurrent with the amine chemistry above, we attempted what was at the time a little-explored reaction, addition of hydrazines to alkynes. The first successful catalysts for this r e a c t i o n w e r e p y r r o l e -b a s e d 3 a n d T i -(SC 6 F 5 ) 2 (NMe 2 ) 2 (NHMe 2 ) (7).…”

Section: Introductionmentioning

confidence: 99%

Titanium-Catalyzed Multicomponent Couplings: Efficient One-Pot Syntheses of Nitrogen Heterocycles

2015

Self Cite

View full text Add to dashboard Cite

Nitrogen-based heterocycles are important frameworks for pharmaceuticals, natural products, organic dyes for solar cells, and many other applications. Catalysis for the formation of heterocyclic scaffolds, like many C-C and C-N bond-forming reactions, has focused on the use of rare, late transition metals like palladium and gold. Our group is interested in the use of Earth-abundant catalysts based on titanium to generate heterocycles using multicomponent coupling strategies, often in one-pot reactions. To be of maximal utility, the catalysts need to be easily prepared from inexpensive reagents, and that has been one guiding principle in the research. For this purpose, a series of easily prepared pyrrole-based ligands has been developed. Titanium imido complexes are known to catalyze the hydroamination of alkynes, and this reaction has been used to advantage in the production of α,β-unsaturated imines from 1,3-enynes and pyrroles from 1,4-diynes. Likewise, catalyst design can be used to find complexes applicable to hydrohydrazination, coupling of a hydrazine and alkyne, which is a method for the production of hydrazones. Many of the hydrazones synthesized are converted to indoles through Fischer cyclization by addition of a Lewis acid. However, more complex products are available in a single catalytic cycle through coupling of isonitriles, primary amines, and alkynes to give tautomers of 1,3-diimines, iminoamination (IA). The products of IA are useful intermediates for the one-pot synthesis of pyrazoles, pyrimidines, isoxazoles, quinolines, and 2-amino-3-cyanopyridines. The regioselectivity of the reactions is elucidated in some detail for some of these heterocycles. The 2-amino-3-cyanopyridines are synthesized through isolable intermediates, 1,2-dihydro-2-iminopyridines, which undergo Dimroth rearrangement driven by aromatization of the pyridine ring; the proposed mechanism of the reaction is discussed. The IA-based heterocyclic syntheses can be accomplished start to finish (catalyst generation to heterocyclic synthesis) in a single vessel. The catalyst can be formed in situ from commercially available Ti(NMe2)4 and the protonated form of the ligand. Then, the primary amine, alkyne, and isonitrile are added to the flask, and the IA product is synthesized. The volatiles are removed (if necessary), and the next reagent is added. A brief video showing the process for the simple heterocycle 4-phenylpyrazole from phenylacetylene, cyclohexylamine, tert-butylisonitrile, and hydrazine hydrate is included. Further development in this field will unlock new, efficient reactions for the production of carbon-carbon and carbon-nitrogen bonds. As an example of such a process recently discovered, a catalyst for the regioselective production of pyrazoles in a single step from terminal alkynes, hydrazines, and cyclohexylisonitrile is discussed. Using titanium catalysis, many heterocyclic cores can be accessed easily and efficiently. Further, the early metal chemistry described is often orthogonal to late metal-based reactions, whi...

show abstract

Pyrrole Syntheses Based on Titanium‐Catalyzed Hydroamination of Diynes.

Cited by 3 publications

References 2 publications

Catalytic Carbodiimide Guanylation by a Nucleophilic, High Spin Iron(II) Imido Complex

Catalytic Carbodiimide Guanylation by a Nucleophilic, High Spin Iron(II) Imido Complex

Photoredox Selective Homocoupling of Propargyl Bromides

Titanium-Catalyzed Multicomponent Couplings: Efficient One-Pot Syntheses of Nitrogen Heterocycles

Contact Info

Product

Resources

About