Developments in Direct CH Arylation of (Hetero)Arenes under Microwave Irradiation

Sharma, Abhishek; Vacchani, Dipak; Eycken, Erik V. Van der

doi:10.1002/chem.201201868

Cited by 63 publications

(24 citation statements)

References 90 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Decreasing the reaction temperature to 130 °C failed to afford a satisfactory result (Table , entry 9). Although the use of microwave irradiation to accelerate the reaction was also examined, neither the yield nor the regioselectivity was improved . It is worth noting that the formation ratio of 1 a / 2 a was almost constant, which indicates that the second arylation of 1 a leading to 2 a occurred competitively during the first arylation of the parent azulene.…”

Section: Resultsmentioning

confidence: 99%

Palladium‐Catalyzed Direct Arylation of Azulene Based on Regioselective C−H Bond Activation

et al. 2016

View full text Add to dashboard Cite

An efficient synthesis of arylazulenes involving minimal steps was developed. The combination of Pd(OAc) 2 / XPhos as ac atalysta nd pivalica cid as an additive was key for the direct arylation of CÀHb onds, and the reactionp roceeded preferentially at the 1-and 3-positions of azulene, without heteroatom-containing directing groups. Compared with the traditional cross-coupling protocol, the arylation method described here requires fewer steps and uses commerciallya vailables ynthetic blocks. The degree of conjugation and the optical properties of the resulting azulenec onjugates can be adjusted by simple protonation, whicha llows the current method to be an efficient strategy for exploiting novel azulene-based functional materials.[a] Dr.

show abstract

Section: Resultsmentioning

confidence: 99%

Palladium‐Catalyzed Direct Arylation of Azulene Based on Regioselective C−H Bond Activation

et al. 2016

View full text Add to dashboard Cite

show abstract

“…[1] In heterocycles with multiple C À Hg roups,i tw ould be highly advantageous to be able to choose which CÀHg roup is functionalized, ideally with complete selectivity and with the ability to "switch" regioselectivity at will. [2] Seminal examples of this approach include the vinylation or arylation of pyrroles and indoles at either C2 or C3, where the outcome is driven by achange in substrate derivatization, [3,4] solvent, [5] or oxidant.…”

mentioning

confidence: 99%

Catalyst‐Switchable Regiocontrol in the Direct Arylation of Remote CH Groups in Pyrazolo[1,5‐a]pyrimidines

2015

View full text Add to dashboard Cite

The regiodivergent palladium-catalyzed C À Ha rylation of pyrazolo [1,5-a]pyrimidine has been achieved, wherein the switch in regioselectivity between positions C3 and C7 is under complete catalyst control. Ap hosphinecontaining palladium catalyst promotes the direct arylation at the most acidic position (C7), whereas ap hosphine-free catalyst targets the most electron-rich position (C3).The direct CÀHa rylation of heterocyclics ubstrates (Scheme 1) is ap owerful synthetic tool for the construction of functionalized heterocycles.I tm aintains the expediency associated with simple cross-coupling reactions,b ut with greater step economy and lower waste production.[1] In heterocycles with multiple C À Hg roups,i tw ould be highly advantageous to be able to choose which CÀHg roup is functionalized, ideally with complete selectivity and with the ability to "switch" regioselectivity at will.[2] Seminal examples of this approach include the vinylation or arylation of pyrroles and indoles at either C2 or C3, where the outcome is driven by achange in substrate derivatization, [3,4] solvent, [5] or oxidant.[6]In these cases,the site selectivity is typically controlled by prohibiting or encouraging migration between positions C3 and C2. By contrast, we were interested to find out whether site selectivity could be engendered in the arylation of remote CÀHg roups,a nd whether catalyst "tuning" could be employed to drive this selectivity. [7] We report herein the catalyst-controlled switching in regioselectivity between the remote positions C3 and C7 of pyrazolo[1,5-a]pyrimidine (1; Figure 1). We chose this motif [8] because it forms the core of ar ange of biologically active compounds.S pecifically,a ryl-substituted pyrazolo[1,5-a]pyrimidines show antitumor [9] and anti-inflammatory properties, [10] have been examined as hepatitis Cvirus inhibitors and estrogen receptor ligands, [11,12] and are found in the approved sedative agents zaleplon and indiplon as well as in the anxiolytic agent ocinaplon.We began our study with the optimization of the coupling of compound 1 with bromobenzene in the presence of av ariety of palladium sources,w ith and without phosphines, changing solvents,bases,additives,and conditions.The results from this survey are summarized in the Supporting Information, and Scheme 2highlights the optimized conditions. Theu se of the monodentate phosphine ligand SPhos proved crucial to achieving site selectivity at C7, giving the desired product 2a in good yield.[13] NMR and UHPLC/ES-MS analyses of the crude reaction mixture showed at race amount (4 %) of the 3,7-diphenylated product (4a)b ut none of the 3-arylated species 3a,t hus indicating that arylation at C3 can only occur (to avery limited extent) after arylation at C7. [14] Conveniently,the reaction works just as well under air as under an inert atmosphere.The relatively high air stability of SPhos is obviously apivotal factor here.

show abstract

“…Notably, microwave heating has proven to accelerate the direct arylation reactions efficiently, resulting, for the polymerization processes, in increased molecular weights of the final polymers. [63] P3AT…”

Section: Direct Arylationmentioning

confidence: 99%

Organometallic Approaches to Conjugated Polymers for Plastic Solar Cells: From Laboratory Synthesis to Industrial Production

et al. 2014

View full text Add to dashboard Cite

Bequeme Routine: Mehrlagige dünne Polymerfilme wurden durch Elektrophorese auf in Agarose immobilisierten Partikeln angeordnet. Anschließendes Entfernen des Kerns führte zu robusten Kapseln mit unterschiedlichen Polymerzusammensetzungen (siehe Fluoreszenzbild). Dieser Ansatz ermöglicht den vielseitigen und routinemäßigen Aufbau von nano‐ und mikroskaligen Kapseln sowie beschichteten Partikeln in sehr wenigen Prozessschritten.

show abstract

Developments in Direct CH Arylation of (Hetero)Arenes under Microwave Irradiation

Cited by 63 publications

References 90 publications

Palladium‐Catalyzed Direct Arylation of Azulene Based on Regioselective C−H Bond Activation

Palladium‐Catalyzed Direct Arylation of Azulene Based on Regioselective C−H Bond Activation

Catalyst‐Switchable Regiocontrol in the Direct Arylation of Remote CH Groups in Pyrazolo[1,5‐a]pyrimidines

Organometallic Approaches to Conjugated Polymers for Plastic Solar Cells: From Laboratory Synthesis to Industrial Production

Contact Info

Product

Resources

About