35377-96-9Relevant articles and documents
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
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.
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.
