9-fluorenyl group

Ph2CHOC(=NH)CCl3. TMSOTf, CH2CI2, rt. 65-92% yield. The 9-fluorenyl group is prepared similarly in 56-91% yield. 

Bromophenyl)-9-fluorenyl group (BrPhF), a novel group for safety-catch amine protection. BrPhF is relatively acid-stable and can be successfully activated by Pd-catalyzed cross-coupling reaction of the aryl bromide with morpholine, followed by cleavage under mild conditions using dichloroacetic acid and triethylsUane [S. Surprenant, W. D. LubeU, J. Org. Chem. 2006, 71, 84Sj. 

This group was reported to be 6000 times more stable to acid than the trityl group because of destabilization of the cation by the fluorenyl group. 

As observed previously, the values for CT+Ph vary by as much as a factor of two and appear to depend on the value of the reaction constant. The parameters ascertained for electrophilic substitution in the 2-position of fluorene are far less variable. No systematic dependence on p is detectable. The results for desilylation deviate seriously from the general pattern but this observation appears exceptional. Although the limited information does not permit a final conclusion, we believe that the data support the idea that the response of the 2-fluorenyl group to changes in electron demand is negligibly small. 

Danopoulos and co-workers reported on the preparation of NHC ligands with pendant indenyl and fluorenyl groups.19 Deprotonation of the alkyl -indene or -fluorene imidazolium salts with one equivalent of potassium hexamethyldisilazide leads to NHCs functionalised with neutral indene or fluorene moieties (IndH-NHC and F1H-NHC). Further deprotonation with... 

The crystal structure of thiastannirane 87 shows no unusual features save that the C-Sn-S angle is exceptionally acute at 45.7(4)°. The NMR spectra demonstrate that 87 partially dissociates into its stannylene and thiaallene components in solution at room temperature, but the equilibrium is such that resonances can be assigned to 87. The ring Sn and C atoms resonate at —365 and 137 or 149 ppm in the " Sn and C NMR spectra, respectively variable-temperature H NMR studies gave A// = 81.6kJ moP and AA = 197 J mol That 87 is colorless supports the idea noted above that the fluorenyl group in distannirane 74 is the reason the latter is red <19930M4>. 

Electrocyclization is the key step in a route to 4//-imidazoles 1187 and imidazoles 1188. Thus, activation of AT-acylamidines 1183 with trifluoromethanesulfonic anhydride and subsequent condensation with amino compounds 1185 produces l-amino-2,4-diazapenta-l,3-dienes 1186. Deprotonation of 1186 by the use of strong organic bases yields the corresponding 4//-imidazoles 1187 or imidazoles 1188 after amine elimination through an anionic 1,5-electrocyclization reaction. For the cyclization to occur, the amino compound 1185 needs to possess electron-withdrawing substituents such as alkoxycarbonyl or fluorenyl groups (Scheme 290) <2004EJO2567>. 

The overlap of the sodium and potassium 3p and 4p orbitals with the carbon 2p orbitals should not be nearly as effective as that of the lithium 2p. Those metals should therefore form complexes that fit the electrostatic model described in Figure 29 more closely. The potassium ion in (TMED)K fluorenyl is disolvated but not chelated by bridging TMEDA groups. The result is a polymeric system in the solid state with each fluorenyl group coordinated to two potassium atoms (Figure 30). The projection of one of the potassium atoms onto the fluorenyl plane is at a point within the periphery of the five-membered ring and also within 0.2 A of the position predicted for the electrostatic model. 

We can carry this further and ask given a positive point charge in the position noted above for one potassium atom, where is the next minimum in the electrostatic potential—that is, where will the second potassium atom be most likely to coordinate The lowest potential energy minimum calculated for a fluorenyl group with one interacting K atom is on the opposite side of the fluorenyl ring and vertically above the plane just to the inside of the Cu—Ci2 bond of the five-membered... 

The substituents at the asymmetric carbon atoms of the C2 linker between the oxygen atom and the fluorenyl group are either in a trans (29a—c) or in a cis (29d) arrangement. For all compounds NMR spectroscopic data indicate dynamic coordination behavior of the THF ligands in solution similar to... 

Sulfonated poly(arylene ether phosphine oxide)s with fluorenyl groups were synthesized to establish proton exchange membranes (Scheme 42). Triphenylphosphine oxide-based diamino (arylene ethers) were made available (Scheme 43) that were utilized in the synthesis of polyimides. ... 

B. Bae, K. Miyatake, M. Watanabe, Synthesis and properties of sulfonated block copolymers having fluorenyl groups for fuel-cell applications. ACS Applied Materials and Interfaces 2009, 1(6), 1279-1286. 

Fluorenyldialkylphosphines represent another interesting class of trialkyl-phosphines that can be used for Suzuki couphngs of aryl chlorides. Sulfonylation of the aromatic moiety of the fluorenyl group results in a water-soluble ligand that can be used for couplings in aqueous solvent (Equation 2.20) [35-37]. 

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