29124-78-5Relevant articles and documents
Transition-Metal-Free C(sp2)–C(sp2) Cross-Coupling of Diazo Quinones with Catechol Boronic Esters
Che, Chi-Ming,Wu, Kai,Wu, Liang-Liang,Zhou, Cong-Ying
supporting information, p. 16202 - 16208 (2020/07/17)
A transition-metal-free C(sp2)?C(sp2) bond formation reaction by the cross-coupling of diazo quinones with catechol boronic esters was developed. With this protocol, a variety of biaryls and alkenyl phenols were obtained in good to high yields under mild conditions. The reaction tolerates various functionalities and is applicable to the derivatization of pharmaceuticals and natural products. The synthetic utility of the method was demonstrated by the short synthesis of multi-substituted triphenylenes and three bioactive natural products, honokiol, moracin M, and stemofuran A. Mechanistic studies and density functional theory (DFT) calculations revealed that the reaction involves attack of the boronic ester by a singlet quinone carbene followed by a 1,2-rearrangement through a stepwise mechanism.
Cp?Rh(iii) and Cp?Ir(iii)-catalysed redox-neutral C-H arylation with quinone diazides: quick and facile synthesis of arylated phenols
Zhang, Shang-Shi,Jiang, Chun-Yong,Wu, Jia-Qiang,Liu, Xu-Ge,Li, Qingjiang,Huang, Zhi-Shu,Li, Ding,Wang, Honggen
supporting information, p. 10240 - 10243 (2015/06/22)
Cp?Rh(iii)- and Cp?Ir(iii)-catalysed direct C-H arylation with quinone diazides as efficient coupling partners is disclosed. This redox-neutral protocol offers a facile, operationally simple and environmentally benign access to arylated phenols. The reaction represents the first example of Cp?Ir(iii)-catalysed C-H direct arylation reaction.
An efficient procedure for the synthesis of crystalline aryldiazonium trifluoroacetates - Synthetic applications
Colas, Christophe,Goeldner, Maurice
, p. 1357 - 1366 (2007/10/03)
We have developed a very mild procedure for the synthesis of crystalline aryldiazonium trifluoroacetate salts in high yields under anhydrous conditions. Over thirty mono- or polyfunctional aniline derivatives have been diazotized by this method, including water- and acid-sensitive substrates. The o- and p-hydroxyaryldiazonium salts, derived from the corresponding anilines, could be deprotonated by treatment with K2CO3 to yield pure diazoquinones. NMR and UV/Vis spectra have been recorded for all the synthesized salts; the data are in good agreement with the rather limited published data and constitute a first extensive report of 13C-NMR chemical shifts in diazonium salts. An excellent linear relationship emerged between Brown's substituent constants S+(p) and the 13C(ipso) chemical shifts. The diazonium salts obtained proved to be much more soluble in organic solvents than their tetrafluoroborate counterparts. They were tested in Pd-mediated coupling reactions of various carbon-carbon double bonds, and were found to give good yields within short reaction times under very mild conditions. We believe that diazonium trifluoroacetates represent a very attractive alternative to diazonium tetrafluoroborates.
IR and UV matrix photochemistry and solvent effects: the isomerization of diazocyclohexadienones (ortho quinone diazides) - detection of molecules with the 1,2,3-benzoxadiazole structure. A UV/Vis and IR absorption and UV photoelectron spectroscopic investigation
Schweig, Armin,Baumgartl, Horst,Schulz, Reinhard
, p. 135 - 172 (2007/10/02)
6-Diazo-2,4-cyclohexadienone and derivatives with fluoro, chloro, methyl, tert-butyl and methoxy substituents have been investigated by UV/Vis absorption, IR absorption and UV photoelectron spectroscopy.Spectral results obtained in the gas phase, in an argon matrix at 10 K and in n-hexane solution at room temperature reveal an equilibrium with the respective 1,2,3-benzoxadiazole isomers, thus disproving current textbook opinions.The 1,2,3-benzoxadiazole structure is derived from the agreement of observed and calculated vertical ionization energies, characteristic IRand UV/Vis absorption bands as well as selective IR and UV photochemical transformations.The relative concentration of the respective 1,2,3-benzoxadiazole in equilibrium with the diazoketone isomer strongly depends on the substituents and on solvent effects.The diazoketone structure is stabilized by hydrogen bonding and polar interactions.The most stable 1,2,3-benzoxadiazole in this study, the 5,7-di-tert-butyl derivative, is at least 6.3 kJ mol-1 more stable than its diazocyclohexadienone valence isomer, whereas 2,3,4,5-tetrafluoro-6-diazo-2,4-cyclohexadienone and 3-methoxy-6-diazo-2,4-cyclohexadienone did not isomerize to a notable extent.Energetic considerations for the stabilization of 1,2,3-oxadiazoles are discussed and compared with experimental and theoretical findings.
