57028-29-2Relevant academic research and scientific papers
Direct C-H bond arylation of fluorenes with aryl chlorides catalyzed by N-heterocyclic carbene-palladium(ii)-1-methylimidazole complex and further transformation of the products in a one-pot procedure
Ji, Ya-Yun,Lu, Li-Li,Shi, Yu-Chun,Shao, Li-Xiong
, p. 8488 - 8498 (2014/12/10)
We report here the NHC-Pd(ii)-Im complex 1-catalyzed direct C-H bond functionalization of the C9 position of fluorenes with aryl chlorides and further transformation of the resulting products in a one-pot procedure. Under the optimal conditions, arylated fluorenes can be obtained in moderate to almost quantitative yields using various activated and unactivated (hetero)aryl chlorides as the arylating reagents. Furthermore, if the mixture from the arylation reaction is exposed to air, the C9-oxidized products can be obtained in acceptable to good yields in a one-pot procedure. In addition, alkyl groups can also be efficiently introduced to the above mixture from the arylation reaction, producing further C9-alkylated products in good to almost quantitative yields in a one-pot procedure, thus providing an expedient, inexpensive and practical strategy for the mono- and di-functionalization of fluorenes. This journal is
Modular access to 9,9-spirobifluorenes by oxidative coupling using molybdenum pentachloride
Trosien, Simon,Schollmeyer, Dieter,Waldvogel, Siegfried R.
supporting information, p. 1160 - 1164 (2013/06/04)
The strong oxidizing agent molybdenum pentachloride was used for an efficient direct C-C bond formation of 9,9-diarylfluorenes to the corresponding 9,9-spirobifluorenes. Thus, a versatile method that is compatible with labile groups, such as iodo moieties
Tricylic amino-acid derivatives
-
, (2008/06/13)
Described herein are compounds which have the general formula: or a prodrug or pharmaceutically acceptable salt, solvate or hydrate thereof wherein: R1 is selected from the group consisting of H, alkyl and the counter ion for a basic addition salt; X is selected from the group consisting of CR9R10, S, O, SO, SO2, NH and N-alkyl; R2, R3, R4, R9 and R10 are independently selected from the group consisting of H and alkyl; R5 and R6 are independently selected from the group consisting of H, alkyl and phenyl, or, alternatively, R5 and R6 together may form a methylene group or a 3- to 6-membered a spirocyclic group; wherein, when X is CR9R10, one or both pairs of R5 and R9 or R6 and R10 may join to form a double or triple bond R7 is selected from the group consisting of Formula II-V: which are all optionally substituted, at nodes other than R8, with 1-4 substituents independently selected from the group consisting of alkyl, halo, aryl (which may be substituted as for R8), trifluoromethyl, trifluoromethoxy, nitro, cyano, amino, mono-alkylamino, di-alkylamino, alkoxycarbonyl, alkylcarbonyl, alkoxythiocarbonyl, alkylthiocarbonyl, alkoxy, alkylS-, phenoxy, -SO2NH2, -SO2NHalkyl, -SO2N(alkyl)2 and 1,2-methylenedioxy; and wherein any of the benzo-fused rings in structures II to V may be replaced by a 5- or 6-membered heterocyclic ring selected from the group consisting of pyridine, thiophene, furan and pyrrole; wherein R8 is selected from the group consisting of H, alkyl, benzyl, cycloalkyl, indanyl and an optionally substituted aryl group, wherein the optional substituents are independently selected from 1-4 members of the group consisting of alkyl, halo, aryl, trifluoromethyl, trifluoromethoxy, nitro, cyano, amino, mono-alkylamino, di-alkylamino, alkoxycarbonyl, alkylcarbonyl, alkoxythiocarbonyl, alkylthiocarbonyl, alkoxy, alkylS-, phenoxy, -SO2NH2, -SO2NHalkyl, -SO2N(alkyl)2 and 1,2-methylenedioxy; -represents a single or double bond; Y is selected from the group consisting of O, S, SO, NH, N-alkyl, CH2, CH-alkyl, C(alkyl)2, and C=O; Z is selected from the group consisting of CH2, O, S, NH and N-alkyl when-is a single bond; Z is selected from the group consisting of CH and N when-is a double bond. Also described is the use of these compounds as pharmaceuticals.
Flash photolysis study of a Friedel-Crafts alkylation. Reaction of the photogenerated 9-fluorenyl cation with aromatic compounds
McClelland, Robert A.,Cozens, Frances L.,Li, Jianhui,Steenken, Steen
, p. 1531 - 1544 (2007/10/03)
A combination of flash photolysis and product analysis is employed to investigate the reaction of aromatic compounds (ArH) with the 9-fluorenyl cation (Fl+) photogenerated from 9-fluorenol in 1,1,1,3,3,3-hexafluoroisopropyl alcohol (HFIP).The availability of the photochemical route to Fl+ means that the reaction of benzylic-type cation with ArH can be directly followed by flash photolysis.An additional feature with electron-rich ArH is that the cyclohexadienyl cation is observed to grow as Fl+ decays.Thus both cationic intermediates of a Friedel-Crafts alkylation are observed in the same experiment.The formation of the cyclohexadienyl cation is demonstrated to be reversible, or at least quasi-reversible, with the kinetic analysis furnishing absolute rate constants for the formation of this cation as well as for its loss of H+ and Fl+.Values of kH:kD for benzene:benzene and toluene:toluene are ca. 1.5 and demonstrate that Fl+ addition is at least partly reversible with these compounds as well.The Hammett ρ+ value obtained for a series of the less electron-rich ArH is -8, indicative of a transition state with considerable cyclohexadienyl cation character.Anisole shows a negative deviation from from Hammett correlation line, explained by the addition of Fl+ to ArH becoming encounter-controlled.This behaviour is dramatically illustrated in a comparison of data for Fl+ and Br2.For the less electron-rich ArH, rate constants for the two electrophiles are parallel.However, from m-xylene through pentamethylbenzene, the rate with Fl+ is unchanged, while the rate with Br2 increases over 1000-fold.The concept of encounter control with Fl+ is strongly supported by the absolute rate constants, which for the electron-rich ArH are all in the range 1-2 E9 dm3 mol-1 s-1, a magnitude typical of diffusion-controlled reactions.The electron-rich ArH also show no intermolecular selectivity since their reactions are encounter-controlled, but have a high intramolecular selectivity.It is suggested that a factor influencing the latter is the reversibility of formation of the cyclohexadienyl cation from the encounter complex.
Reactivities of 9-Arylfluoren-9-yl and 1-(4-Dimethylaminophenyl)ethyl Cations in Water and Trifluoromethanol Studied by Laser Flash Photolysis
Cozens, Frances L.,Mathivanan, N.,McClelland, Robert A.,Steenken, Steen
, p. 2083 - 2090 (2007/10/02)
9-Arylfluoren-9-yl cations have been observed as transient intermediates upon 248 nm laser photolysis of 9-arylfluoren-9-ols in 2,2,2-trifluoroethanol (TFE) and 1:4 (v/v) acetonitrile-water.Quantum yields for the formation of the cations were measured and found to lie in the range 0.5-0.8.Rate constants for the decay of the cations in the two solvents parallel each other, a plot of log kTFE versus log kw being linear with a slope of 1.00.These rate constants are approximately two orders of magnitude larger than those observed in the same solvent for the corresponding monosubstituted triarylmethyl cations.Substituent effects in the two series are similar.For both the hydration reaction and the overall equilibrium, a two-parameter treatment dissecting the substituent contributions into resonance and polar effects shows that the former are more important in the triarylmethyl series, while the latter are more important in the fluorenyl series.Twisting of the 9-aryl ring out of coplanarity with the fluorenyl ring is the likely cause of the diminished resonance interaction in this system.The 1-(4-dimethylaminophenyl)ethyl cation has been observed in TFE and 1:1 TFE-W, being generated by photoprotonation of 4-dimethylaminostyrene.Rate constants for decay are about 50 times smaller than those previously estimated by a clock method.The failure of the latter approach is associated with the rate constant for the clock nucleophile becoming significantly less than diffusion control for this highly stable cation.An extended log kw-pKR correlation is constructed.This shows a series of reasonably parallel lines associated with different families.In considering cations with the same pKR, the order of inherent reactivity is 9-unsubstituted-9-xanthylium ca. cyclic dialkoxy-carbocation > phenyltropylium > diarylmethyl ca. 9-arylxanthylium > triarylmethyl ca. 9-arylfluoren-9-yl.The log kw-pKR data for each family are reasonably satisfied by a linear relationship, with a slope d(log kw)/dpKR of 0.6+/-0.1.The triarylmethyl and 9-arylfluoren-9-yl cations form a contiguous series covering 26 pKR units.The data for these indicate that there is probably a gentle downward curvature in the correlation, particularly at the high reactivity end.This is consistent with a Hammond effect on the transition state such that it becomes more cation-like in the hydration direction for more reactive cations.
