29574-51-4Relevant academic research and scientific papers
Phenanthrene Synthesis by Palladium-Catalyzed Benzannulation with o-Bromobenzyl Alcohols through Multiple Carbon-Carbon Bond Formations
Iwasaki, Masayuki,Araki, Yasuhiro,Nishihara, Yasushi
, p. 6242 - 6258 (2017/06/23)
A palladium-catalyzed benzannulation with o-bromobenzyl alcohols enabled the facile construction of phenanthrene skeletons via the sequential multiple carbon-carbon bond formations. A variety of multisubstituted phenanthrenes were synthesized by the reaction of (Z)-β-halostyrenes with o-bromobenzyl alcohols as well as by the three-component coupling of alkynes, aryl bromides, and o-bromobenzyl alcohols. The electron-deficient phosphine ligand played an important role to control the sequential oxidative addition of two different organic halides employed, which realized the selective formation of the desired phenanthrenes in good yields. This synthetic protocol was also applicable to the synthesis of the highly fused polycyclic aromatic hydrocarbons such as tetraphenes.
Substitution controlled functionalization of ortho -bromobenzylic alcohols via palladium catalysis: Synthesis of chromenes and indenols
Mahendar, Lodi,Satyanarayana, Gedu
, p. 2059 - 2074 (2014/04/03)
An efficient domino Pd-catalyzed transformation of simple ortho-bromobenzyl tertiary alcohols to chromenes is presented. Their formation is believed to proceed via the formation of a five-membered palladacycle, which, in turn, involves in an intermolecular homocoupling with the second ortho- bromobenzyltertiary alcohol to yield the homo-biaryl bond followed by intramolecular C-O bond formation. Interestingly, when there is an allylic substituent on the benzylic carbon atom, a chemoselective switch was observed, which preferred intramolecular Heck coupling and gave indenols. Further, it has been confirmed that the tertiary alcohol functionality is indispensible to give the coupled products, whereas the use of primary/secondary benzylic alcohols furnished the simple carbonyl products via a possible reductive debromination followed by oxidation due to the availability of β-hydrogen(s).
Palladium-catalyzed annulation of o-iodobiphenyls with o-bromobenzyl alcohols: Synthesis of functionalized triphenylenes via C-C and C-H bond cleavages
Iwasaki, Masayuki,Iino, Shohei,Nishihara, Yasushi
, p. 5326 - 5329 (2013/11/06)
Treatment of o-iodobiphenyls with o-bromobenzyl alcohols in the presence of cesium carbonate under palladium catalysis affords a series of highly substituted triphenylenes. The reaction involves two C-C bond formations and C-C and C-H bond cleavages. A combination of palladium and an electron-deficient phosphine ligand proves to be effective for both decarbonylative cross-coupling and intramolecular cyclization.
Palladium-catalyzed arylation of α,α-disubstituted arylmethanols via cleavage of a C-C or a C-H bond to give biaryls
Terao, Yoshito,Wakui, Hiroyuki,Nomoto, Michiyo,Satoh, Tetsuya,Miura, Masahiro,Nomura, Masakatsu
, p. 5236 - 5243 (2007/10/03)
The palladium-catalyzed arylation of α,α-disubstituted arylmethanols with aryl halides proceeds not only via C-H bond cleavage at the ortho-position, but also via cleavage of the sp2-sp3 C-C bond with the liberation of ketones (β-carbon elimination) to give the corresponding biaryls. Both reactions appear to occur through common arylpalladium(II) alcoholate intermediates. The results of systematic studies with respect to which C-C or C-H bond is preferentially cleaved in the arylation are reported. Among the important findings is the selective elimination of ortho-substituted aryl groups even from aryl(diphenyl)methanols due to steric reasons. Thus, various biaryls having ortho-substituents can be produced efficiently by treatment of the corresponding aryl(diphenyl or dimethyl)methanols with aryl bromides and chlorides.
Photocyclization of 2-(2′-hydroxyphenyl)benzyl alcohol and derivatives via o-quinonemethide type intermediates
Huang,Beveridge, Kathryn Anne,Wan, Peter
, p. 7676 - 7684 (2007/10/02)
A new photochemical reaction, the photocyclization of 2-(2′-hydroxyphenyl)benzyl alcohol (1) and derivatives to 6H-dibenzo[b,d]pyrans, is reported. The quantum yield for cyclization of 1 to give pyran 7 is 0.,50 ± 0.04 in aqueous solutions of pH > 10. At lower pH, φ is significantly lower. For example at pH 7, φ = 0.25 ± 0.03. Results from investigations of structure-reactivity, pH effects, and fluorescence data suggest a mechanism in which the primary step involves ionization of the phenol moiety to phenolate in S1, which is probably followed by (or is concerted with) twisting of the phenyl rings to give a more planar species in the excited state. This is subsequently followed by (or is concerted with) a dehydroxylation step of the benzyl alcohol moiety (all on the S1 surface) to give an o-quinonemethide type intermediate 20 and deactivation back to the ground-state surface. Electrocyclic ring closure of this intermediate gives the observed pyran. Nucleophilic trapping of this electrophilic intermediate by solvent (e.g., MeOH) to give the methyl ether is also observed when photolysis is carried out in MeOH. The proposed reaction pathway is unprecedented: it takes advantage of the tendency of biphenyl systems to be planar in the excited state as well as the enhanced electron-donating effect of the phenolate anion, which is required for the dehydroxylation step.
