35377-96-9Relevant 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
Carbon-Skeletal Anionic Rearrangements and the ?-Orbital Overlap Constraint: The Question of Nucleophilic Attack versus Electron Transfer
Eisch, John J.,Kovacs, Csaba A.,Chobe, Prabohd
, p. 1275 - 1284 (2007/10/02)
In order to evaluate the geometrical requirements and the actual electronic nature of apparent anionic rearrangements of metalated aromatic hydrocarbons, amines, and ethers, cyclic structural types of such anions were generated as lithium salts by proton abstraction from C-H bonds by RLi or by C-Cl bond cleavage by Li.The cyclic systems examined were anions of 9,9-dimethyl-, 9-methyl-9-benzyl-, and 9-benzyl-9-phenylfluorenes; 9-methyl-9-phenyl-, 9,9-diphenyl-, and 9,9-(2,2'-biphenylene)-9,10-dihydrophenanthrenes; 5-methyl- and 5-phenyl-5,6-dihydrophenathridines;and 9H-dibenzopyran.The anions generated from 9-methyl-9-benzylfluorene, 9-benzyl-9-phenylfluorene, 5-methyl-5,6-dihydrophenanthridine, and 9H-dibenzopyran, as well as 9-methyl-9-(lithiomethyl)fluorene, did not undergo skeletal rearrangement when heated between 40 and 120 deg C for protracted periods.However, the anions derived from the 9-methyl-9-phenyl-, 9,9-diphenyl-, and 9,9-(2,2'-biphenylene)-9,10-dihydrophenanthrenes did undergo rearrangement with a shift of the 9-aryl group.With the anion of 5-phenyl-5,6-dihydrophenanthridine, some shift of the 5-phenyl was observed, but the principal rearrangement was ring contraction with the formation of N-phenyl-9-fluorenylamine.By noting which anions underwent skeletal rearrangement and which competing migrating groups in a given anion underwent a shift preferentially, we have formulated an appropriate geometrical view of the transition states involved.Furthermore, by generating the 2,2,2-triphenylethyl anion (as its lithium salt) from (a) 2-chloro-1,1,1-triphenylethane and Li, (b) 2-bromo-1,1,1-triphenylethane and n-BuLi, and (c) bis(2,2,2-triphenylethyl)mercury and n-BuLi, we attempted to learn whether such shifts were truly nucleophilic or whether SET processes were involved.Evidence for SET processes was obtained for the generation of (2,2,2-triphenylethyl)lithium by method a, but no ESR or CIDNP evidence for radical intermediates was observable when (2,2,2-triphenylethyl)lithium was produced by method c.
Reactions of 9-Substituted Fluorenide Carbanions with Allyl Chlorides by SN2 and SN2' Mechanism
Bordwell, Frederick G.,Clemens, Anthony H.,Cheng, Jin-Pei
, p. 1773 - 1782 (2007/10/02)
The average ratio of SN2 rate constants for benzyl chloride vs. allyl chloride reacting with 9-substituted fluorenide carbanions, 9-G-Fl- (G = Me, PhS, Ph o-tol, or t-Bu), in Me2SO solution is 2.3, which is close to the ratio previously observed for reactions of smaller nucleophiles with more localized charges, such as iodide ion, in various solvents.Broensted plots of log k vs. pKHA (both in Me2SO) are used to calculate reactivity values (r) for 9-G-Fl- ions of the same basicity reacting with allyl chloride.The r values reveal the same order of steric effects for G in these SN2 reactions as was found previously for benzyl chloride, i.e., Me - ions were found to increase progressively and appreciably with γ-methyl substitution, i.e., CH2=CHCH2Cl (1) , MeCH=CHCH2Cl (4) , Me2C=CHCH2Cl (5), whereas the Broensted β values decreased progressively.The second-order rate constants for reactions with families of 9-G-Fl- ions were found to follow a somewhat different pattern for α-methyl substitution, i.e., CH2=CHCH2Cl (1) > CH2=CHCH(Me)Cl (2) CH2=CHC(Me)2Cl (3); the rate differences were small, but the β values again decreased progressively.Product studies indicated that 1 reacts with 9-G-Fl- ions by an SN2 mechanism but that 2 gives SN2' products in a amounts increasing along the series G = Me, Ph, o-tol, t-Bu; 3 appears to give only SN2' products.The rates of reactions of 9-CN-Fl- and 9-CO2MeFl- ions with 3 to form SN2' and SN2 products are independent of the carbanion concentration.The first-order reaction of 9-CN-Fl- ion with t-BuCl in MeOH gives 17percent yield of 9-CN-9-t-BuFl.Entalpies of activation for SN2 reactions of 9-G-Fl- ions reacting with 5 are 7-9 kcal/mol lower, and entropies of activation are 18, or more, eu units less positive than for SN2' reactions of 9-G-Fl- ions with 3.Mechanism for SN2' reactions are discussed in light of these findings.
Rate-Equilibrium Relationships for Reactions of Families of Carbanion Nucleophiles with N-Benzyl-N,N-dimethylanilinium Cations and with Alkyl Chlorides, Bromides, and Iodides
Bordwell, Frederick G.,Hughes, David L.
, p. 7300 - 7309 (2007/10/02)
Rates of reaction of a family of 9-methylfluorenide anions, 9-MeFl-, with 15 substituted N-benzyl-N,N-dimethylanilinium cations, GC6H4CH2N(Me)2C6H4Y+, were measured in a 0.8 M KNO3 solution of Me2SO at 25 deg C.Substitution in the benzyl moiety produced a U-shaped Hammett plot, with m-CN reacting 9- to 15-fold faster than H and p-MeO reacting 1.5- to 3-fold faster than H, depending on the basicity of the 9-RFl- ion.Broensted ΒNu values obtained by varying nucleophile basicity in the 9-MeFl- ion family were 0.28 for N-(p-methoxybenzyl)-N,N-dimethylanilinium ion, 0.33 for N-benzyl-N,N-dimethylanilinium ion, and 0.39 for N-(m-cyanobenzyl)-N,N-dimethylanilinium ion.These βNu values were unaffected by substitution in the aniline portion of the substrate.Hammett pLg values were obtained by substitution of m-Cl, p-Br, H, p-Me and p-MeO groups (Y) in the dimethylaniline leaving group; pLg values were all near 2.0 and were insensitive to the basicity of the attacking nucleophile and the substituent G in the benzyl group of the substrate. βNu values for families of 9-RFl- ions reacting with ArCH2X, n-BuX, and CNCH2X also remained constant as the leaving group, X, was changed (Cl, Br, and I) for a given substrate and when the donor atom was changed along the series C-, N-, O-, and S-.These results indicate that there is no direct relationship between the size of βNu and the extent of bond making or bond breaking in the transition state for SN2 reactions, as has been generally assumed in theoretical attempts to rationalize the effects of structural variations on rate.It is suggested that SN2 reactions occur in two stages.The size of βNu is determined in the first stage where an ion-dipole complex is formed.The rate is determined largely in the second stage where bonds are formed and cleaved and where molecular and solvent reorganization occurs.
Hammett and Broensted-Type Relationships in Reactions of 9-Substituted Fluorenyl Anions with Benzyl Halides
Bordwell, Frederick G.,Hughes, David L.
, p. 3320 - 3325 (2007/10/02)
The rates of reaction of 9-substituted fluorenyl anions, 9-G-Fl- (G=CN, Ph, Me), with substituted benzyl chlorides (p-MeO, p-Me, m-Me, p-F, p-Cl, m-Cl, m-CF3, m-NO2) in Me2SO solution have been measured.A "U-shaped" Hammett plot was obtained for 9-CN-Fl- (ρmeta 1.3), but a "normal" Hammett plot was obtained with 9-Ph-Fl- (ρ = 1.8), which is 9.6 pK units more basic.Broensted-type plots of log k vs. pKa obtained for three 9-G-Fl- families (9-PhSO2, 9-PhS, and 9-Ph) reacting with m-CF3C6H4CH2Cl gave slopes (βNu) near 0.4.The βNu values for the 9-Ph-Fl- family reacting with ArCH2Cl were increased by the presence of electron accepting substituents, p-MeO (0.30), H (0.365), m-CF3 (0.45), m-NO2 (0.485).The small increases in Hammett ρ values and βNu values caused by electron-withdrawing substituents in ArCH2Cl are interpreted to mean that there is a small increase in the negative charge density in the benzylic carbon atom and/or chlorine atom in the transition state.Rates for the reaction of PhCH2Br with eight 9-G-Fl- anions were measured.For 9-CN-Fl- the kBr/kCl rate ratio was found to be 4 times larger in Me2SO than in EtOH.The reactivity-selectivity principle is discussed and the conclusion drawn that it should be abandoned.
A Direct Relationship between Nucleophilicity and Basicity in SN2 Reactions of Fluorenyl Anions with Benzyl Chloride in Dimethyl Sulfoxide Solution
Bordwell, Frederick G.,Hughes, David L.
, p. 3314 - 3320 (2007/10/02)
The rates of reactions for nine 9-substituted fluorenyl anions, 9-G-Fl- (G=CN, CO2Me, PhSO2, PhS, Ph, PhO, PhCH2, Me, t-Bu), reacting with benzyl chloride in Me2SO solution have been measured.For 9-CN-Fl- the rates increased with sol
