Synthesis, Structural Characterization, and Reactivity of a Fluorene

Mar 31, 2015 - ABSTRACT: Direct deprotonation of 9-fluorenol with Ca[N-. (SiMe3)2]2 efficiently generated a fluorene-based calcium oxycyclopentadienid...
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Synthesis, Structural Characterization, and Reactivity of a FluoreneBased Calcium Oxycyclopentadienide Complex Baosheng Wei,† Heng Li,† Wen-Xiong Zhang,*,† and Zhenfeng Xi*,†,‡ †

Beijing National Laboratory for Molecular Sciences (BNLMS), Key Laboratory of Bioorganic Chemistry and Molecular Engineering of Ministry of Education, College of Chemistry, Peking University, Beijing 100871, China ‡ State Key Laboratory of Organometallic Chemistry, Shanghai Institute of Organic Chemistry (SIOC), Chinese Academy of Sciences, Shanghai 200032, China S Supporting Information *

ABSTRACT: Direct deprotonation of 9-fluorenol with Ca[N(SiMe3)2]2 efficiently generated a fluorene-based calcium oxycyclopentadienide complex, which is the first alkaline earth metal complex containing an oxycyclopentadienyl dianion ligand. The η5, η1, and η2 interactions between the oxycyclopentadienyl dianion ligand and the calcium center were observed in the solid state. The calcium oxycyclopentadienide complex displayed reductive character and multiple reactive sites. Its reactivity toward a range of electrophiles, especially acid chlorides, was investigated and discussed in detail. A wide variety of fluorene derivatives were synthesized.

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INTRODUCTION Organocalcium chemistry, as part of organometallic chemistry of heavier alkaline earth metals, has developed rapidly in recent years.1,2 Its chemistry mainly concentrates on the synthesis, structure determination, and catalytic application of some welldefined organocalcium complexes.2 Among all those complexes, ligand design is the most important consideration for the properties and structures of the calcium species.3 Organocalcium metallocenes are among the most extensively studied complexes in this area, because of the easy manipulation on the cyclopentadienyl ring for the steric effect and solubility.1a,4 As a consequence, cyclopentadienyl ligands bearing pendant groups, such as amine,5a ether,5b,c alkenyl,5d and ester5e groups, have been used to construct calcium metallocenes.5,6 In 2009, we isolated and characterized a lithio oxycyclopentadienyl (OCp) dianion, a cyclopentadienyl (Cp) ligand with an exocyclic oxy anion, from the reaction between 1,4-dilithio-1,3-dienes and CO.7,8 As our ongoing interest in the organometallic chemistry of heavier alkaline earth metals,5e,9 we considered that the OCp dianion ligand might be applied for heavier alkaline earth metals. However, no reaction took place between the lithio OCp dianion and calcium salts. We then turned our attention to 9-fluorenol, a commercially available molecule containing both a Cp moiety and a pendant hydroxy group. 9-Fluorenol might be a good precursor to generate an OCp dianion, in which the two benzene ring-fused Cp moiety could be expected to demonstrate different properties from normal Cp rings. Herein, we report the synthesis and structure characterization of a fluorene-based calcium oxycyclopentadienide complex from the reaction of 9-fluorenol and Ca[N(SiMe3)2]2. To the best of our knowledge, it is the first alkaline earth metal complex containing an OCp dianion ligand. In © 2015 American Chemical Society

addition, the reaction chemistry and synthetic application potential of the Ca-OCp complex toward electrophiles and oxidants were investigated, leading to a wide range of fluorene derivatives.10

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RESULTS AND DISCUSSION Treatment of 9-fluorenol with Ca[N(SiMe3)2]2 (1.0 equiv) in THF at room temperature efficiently generated a fluorenebased calcium oxycyclopentadienide complex 1 via a common deprotonation reaction (Scheme 1). This Ca-OCp complex was strongly sensitive to moisture and oxygen but stable under an argon atmosphere at room temperature. Single crystals of complex 1 suitable for X-ray diffraction were obtained via recrystallization from THF at −20 °C. X-ray analysis demonstrates that 1 has four fluorene skeletons with a pseudo C2 symmetry in the solid state (Scheme 1, Figure 1; see the Supporting Information for details).11 The geometry of the structure consists of two similar parts linked by a planar Ca2O2 core.12 The core contains two bridging exocyclic oxygen atoms (O2, O8) and two calcium atoms (Ca2, Ca3), which is analogous to the reported Li2O2 ring.8 Two calcium centers in each part coordinate differently. One calcium atom (Ca1) is attached to the Cp ring of a fluorene skeleton. The distances between Ca1 and carbon atoms in the Cp ring have a narrow range from 2.738(3) to 2.776(3) Å, indicating an η5 mode interaction.13 Ca1 also coordinates with an exocyclic oxygen atom (O1) of another fluorene skeleton. The bond length of this Ca1−O1exocyclic (2.209(2) Å) σ-bond is significantly shorter than Ca−Othf (2.335(2)−2.467(2) Å) bonds. Interestingly, Ca1 Received: January 21, 2015 Published: March 31, 2015 1339

DOI: 10.1021/acs.organomet.5b00059 Organometallics 2015, 34, 1339−1344

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Organometallics Scheme 1. Reaction of 9-Fluorenol with Ca[N(SiMe3)2]2

Scheme 2. Reactions of Complex 1 with Acid Chlorides

When 1 was treated with 1 equiv of tBuCOCl, unexpectedly, the C9-acylated product 4b was generated in 81% yield. When 2 equiv of tBuCOCl was used, the doubly acylated product 2b and the C9-acylated product 4b were both obtained. Based on the above-mentioned results, a proposed reaction mechanism is shown in Scheme 3. The O-acylation might occur Figure 1. ORTEP drawing of 1 with 30% thermal ellipsoids. Hydrogen atoms are omitted for clarity. Selected structural parameters (Å): Ca1−O1 = 2.209(2), Ca1−O3 = 2.376(9), Ca1−O4 = 2.335(2), Ca1−C13 = 2.674(3), Ca1−C26 = 2.763(3), O2−C26 = 1.360(4), O1−C13 = 1.388(4), Ca2−O2 = 2.309(2), Ca2−O1 = 2.297(2), Ca2−O5 = 2.400(2), Ca2−O6 = 2.417(2), Ca2−O7 = 2.467(2), Ca2−O8 = 2.356(2); Ca3−O2 = 2.268(2), Ca3−O8 = 2.269(2), Ca3−O9 = 2.372(7), Ca3−O10 = 2.392(2), Ca3−O11 = 2.246(2), Ca4−O11 = 2.248(3), Ca4−O12 = 2.351(3), Ca4−O13 = 2.376(16), Ca4−C59 = 2.821(3), Ca4−C80 = 2.610(4).

Scheme 3. 1,2-Acyl Migration Mechanism and Derivative Reactions of the Possible Intermediate

also has a bond interaction with the ipso carbon atom (C13). Therefore, Ca1 bonds to the C13Cp-O1exocyclic moiety with an η2 mode, which is extremely rare in the organometallic chemistry of calcium. Another calcium atom (Ca2) is included in the Ca2O2 core, and Ca2 has bonding interactions with exocyclic oxygen atoms (O1, O2, O8) and oxygen atoms (O5, O6, O7) in THF. Similar coordination modes can be found in another side of the Ca2O2 core, which makes up the whole geometry. With the Ca-OCp complex 1 in hand, we turned to investigate its reactivity considering the multiple reactive sites of this OCp dianion. First, the reaction between 1 and acid chlorides was studied (Scheme 2). When 1 was treated with 1 equiv of acetyl chloride, a mixture of the C9-acylated/Oacylated product 2a and the O-acylated product 3a was obtained in 68% combined yield. When 2 equiv of acetyl chloride was used, the doubly acylated product 2a was exclusively obtained in 78% yield. The C9-acylated compound 4a was not observed. These results demonstrated that the Oacylation should be prior to the C-acylation.14 In order to obtain pure O-acylated products, the bulky acid chloride (tBuCOCl) was utilized in consideration of the steric effect.8

first and was followed immediately by a 1,2-acyl migration to generate the C9-acylated intermediate 5. Hydrolysis of 5 afforded the product 4b.15 Furthermore, when 4-I-PhCOCl and Me3SiCl were used to capture 5, the corresponding products 6a and 6b could be obtained in good yields, respectively. The structure of 6a was confirmed by X-ray single-crystal diffraction analysis (Figure 2). To gain more experimental evidence for the O-acylation/1,2acyl migration process, the bulkier AdCOCl was tried. When 1 was treated with 1 equiv of AdCOCl, the O-acylated product 7 was successfully isolated in 80% yield (Scheme 4a). When this reaction was carried out at room temperature for 20 h, the acyl migration product 8 was isolated only in 31% yield after 1340

DOI: 10.1021/acs.organomet.5b00059 Organometallics 2015, 34, 1339−1344

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Organometallics

Table 1. Reactions of Complex 1 with Other Electrophiles or Oxidantsd

Figure 2. ORTEP drawing of 6a with 30% thermal ellipsoids. Hydrogen atoms are omitted for clarity.

Scheme 4. Evidence for O-Acylation/1,2-Acyl Migration Stepwise Process

a

1.0 equiv and the others 2.0 equiv. bIsolated yields. cFor 2 h. Electrophiles or oxidants were added in −78 °C and reacted at r.t. for 1 h. d

hydrolysis. This indicated that the 1,2-acyl migration process might be very slow. In addition, we performed the reaction of 7 with Ca[N(SiMe3)2]2 (Scheme 4b).5e The product 8 was efficiently generated in 87% isolated yield within 2 h, which, in turn, demonstrated that a C9-Ca intermediate would undergo the subsequent 1,2-acyl migration more rapidly. Next, the reaction of 1 with other electrophiles and oxidants was investigated. As shown in Table 1, when oxidants such as halogen and air were used, fluorenone 9 was obtained (entries 1−3), displaying the reductive character of dianion systems.8 Alkyl electrophiles preferred to attack to the C9 position of the skeleton, and the C9-substituted fluorenols 10−12 were readily afforded (entries 4−6). In comparison, for the preparation of such C9-substituted fluorenols, organometallic reagents as nucleophiles are usually needed. 16 When 2 equiv of trimethylsilyl chloride was applied, the doubly silylated product 13 was obtained (entry 7). Furthermore, the tandem C9alkylation/O-acylation or O-silylation could be achieved, as shown in Scheme 5. In this condition, the allyl bromide was proposed to directly capture on the C9 position; then acylation and silylation would ensue, respectively, when MeCOCl and Me3SiCl were added to the reaction. Then, in order to investigate the substrate scope of fluorenol molecules, we introduced some substituents on the fluorene skeleton 16. As shown in Scheme 6, the phenyl, alkyl, and bromo substituted Ca-OCp complexes 1-R (R = Ph, tBu, and Br) were in situ generated. A wide range of fluorene derivatives 17−20 were thus synthesized by treatment of 1-R with different electrophiles. Notably, access to these compounds by other means is generally very difficult. In summary, we have synthesized and structurally characterized a fluorene-based calcium oxycyclopentadienide complex. The reaction chemistry and synthetic application of the Ca-

Scheme 5. Tandem C9-Alkylation/O-Acylation or OSilylation

OCp complex were investigated, leading to a wide range of fluorene derivatives.

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EXPERIMENTAL SECTION

General Procedures. All reactions were carried out under a slightly positive pressure of dry and oxygen-free argon by using standard Schlenk line techniques or under an argon atmosphere in a Mikrouna Super (1220/750) Glovebox. The argon in the glovebox was constantly circulated through a copper/molecular sieves catalyst unit. The oxygen and moisture concentrations in the glovebox atmosphere were monitored by an O2/H2O Combi-Analyzer to ensure both were always below 1 ppm. Unless otherwise noted, all starting materials were commercially available and were used without further purification. Ca[N(SiMe3)2]2(Et2O)1/2 was prepared according to a literature method with the only change of solvent from THF to Et2O.17 Solvents were purified by an Mbraun SPS-800 Solvent 1341

DOI: 10.1021/acs.organomet.5b00059 Organometallics 2015, 34, 1339−1344

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142.04, 142.14, 178.01, 206.38. HRMS calcd for C23H26O3Na [M + Na]+: 373.1774, found 373.1776. Synthesis of Compound 6. To a THF solution of 9-fluorenol (182 mg, 1.0 mmol) in a 25 mL Schlenk tube, Ca[N(SiMe3)2]2(Et2O)1/2 (398 mg, 1.0 mmol) was added. The reaction mixture became black immediately and was stirred at room temperature for 1 h. tBuCOCl (121 mg, 1.0 mmol) was added at −78 °C, and the reaction mixture can be elevated to room temperature. After the reaction mixture was stirred at room temperature for 0.5 h, 4-IPhCOCl (266 mg, 1.0 mmol) or Me3SiCl (109 mg, 1.0 mmol) was added. After another 1.0 h and workup, the residue was purified by column chromatography to give products 6a and 6b. 6a. Colorless solid, isolated yield 66% (0.66 mmol, 329 mg). 1H NMR (400 MHz, CDCl3, SiMe4): δ 0.88 (s, 9H, CMe3), 7.31−7.35 (m, 2H, CH), 7.46−7.50 (m, 2H, CH), 7.70−7.74 (m, 6H, CH), 7.79 (d, J = 7.6 Hz, 2H, CH); 13C NMR (100 MHz, CDCl3, SiMe4): δ 27.25, 45.04, 92.42, 100.82, 120.44, 127.58, 128.28, 129.77, 130.47, 131.38, 137.55, 141.55, 142.12, 165.70, 206.08. HRMS calcd for C25H21IO3Na [M + Na]+: 519.0428, found 519.0425. Recrystallization of 6a from Et2O/hexane (2/1) solvents at room temperature gave single crystals suitable for X-ray analysis. 6b. Colorless solid, isolated yield 73% (0.73 mmol, 246 mg). 1H NMR (400 MHz, CDCl3, SiMe4): δ −0.27 (s, 9H, SiMe3), 1.34 (s, 9H, CMe3), 7.22−7.26 (m, 2H, CH), 7.34−7.38 (m, 4H, CH), 7.62−7.64 (m, 2H, CH); 13C NMR (100 MHz, CDCl3, SiMe4): δ 1.27, 26.92, 45.58, 92.13, 120.27, 124.43, 127.79, 129.24, 141.10, 148.08, 213.84. HRMS calcd for C21H26SiO2Na [M + Na]+: 361.1594, found 361.1602. Synthesis of Compound 7. To a THF solution of 9-fluorenol (91 mg, 0.5 mmol) in a 25 mL Schlenk tube, Ca[N(SiMe3)2]2(Et2O)1/2 (198 mg, 0.5 mmol) was added. The reaction mixture became black immediately and was stirred at room temperature for 1 h. AdCOCl (100 mg, 0.5 mmol) was added at −78 °C, and the reaction mixture can be elevated to room temperature. After stirring at room temperature for 0.5 h, the reaction solution was quenched with water. After workup, the residue was purified by column chromatography to give product 7. 7. White solid, isolated yield 80% (0.40 mmol, 138 mg). 1H NMR (400 MHz, CDCl3, SiMe4): δ 1.33−1.36 (m, 3H, CH2), 1.44−1.49 (m, 9H, CH2), 1.70 (s, 3H, CH), 5.66 (s, 1H, CH), 7.22−7.31 (m, 4H, CH), 7.40−7.44 (m, 2H, CH), 7.69 (d, J = 7.2 Hz, 2H, CH); 13C NMR (100 MHz, CDCl3, SiMe4): δ 27.72, 36.07, 38.93, 47.20, 86.87, 120.60, 124.50, 128.09, 129.70, 142.02, 144.67, 214.05. HRMS calcd for C24H24O2Na [M + Na]+: 367.1668, found 367.1672. Synthesis of Compound 8. To a THF solution of 7 (344 mg, 1.0 mmol) in a 25 mL Schlenk tube, Ca[N(SiMe3)2]2(Et2O)1/2 (198 mg, 0.5 mmol) was added. The reaction mixture was stirred at room temperature for 2 h. After workup, the residue was purified by column chromatography to give product 8. 8. Colorless solid, isolated yield 87% (0.87 mmol, 299 mg). 1H NMR (400 MHz, CDCl3, SiMe4): δ 1.39−1.53 (m, 12H, CH2), 1.84 (s, 3H, CH), 4.18 (s, 1H, OH), 7.34−7.42 (m, 3H, CH), 7.61−7.68 (m, 2H, CH), 7.78−7.90 (m, 3H, CH); 13C NMR (100 MHz, CDCl3, SiMe4): δ 28.71, 36.30, 36.51, 42.66, 83.91, 122.84, 123.37, 126.21, 127.84, 127.99, 128.42, 129.21, 131.06, 131.22, 135.01, 137.23, 138.89, 205.04. HRMS calcd for C24H24O2Na [M + Na]+: 367.1668, found 367.1665. 8′. The title compound is the H/D exchange product of 8 and d4CH3OH, and 8′ proves the existence of a hydroxy group in 8. 1H NMR (400 MHz, CDCl3, SiMe4): δ 1.38−1.53 (m, 12H, CH2), 1.83 (s, 3H, CH), 4.18 (s, 0.4H, OH/D), 7.32−7.40 (m, 3H, CH), 7.61− 7.66 (m, 2H, CH), 7.77−7.88 (m, 3H, CH). Procedure for the Reactions of Complex 1 with Other Electrophiles or Oxidants. To a THF solution of 9-fluorenol (91 mg, 0.5 mmol) in a 25 mL Schlenk tube, Ca[N(SiMe3)2]2(Et2O)1/2 (198 mg, 0.5 mmol) was added. The reaction mixture became black immediately and was stirred at room temperature for 1 h. Electrophiles or oxidants were added at −78 °C, and the reaction mixture can be elevated to room temperature. After stirring at room temperature for 1

Scheme 6. Substrate Scope of Fluorenol Compounds

Purification System and dried over fresh Na chips in the glovebox. 1H and 13C NMR spectra were recorded on a Bruker-400 spectrometer (FT, 400 MHz for 1H; 100 MHz for 13C) at room temperature. Chemical shifts were reported in units (ppm) by assigning TMS resonance in the 1H NMR spectrum as 0.00 ppm. High-resolution mass spectra (HRMS) were recorded on a Bruker Apex IV FTMS mass spectrometer using ESI (electrospray ionization). Isolation of Complex 1. To a THF solution of 9-fluorenol (91 mg, 0.5 mmol) in a 25 mL Schlenk tube, Ca[N(SiMe3)2]2(Et2O)1/2 (198 mg, 0.5 mmol) was added. The reaction mixture became black immediately and was stirred at room temperature for 1 h. The reaction mixture was reduced under vacuum, and the residue was washed with hexane/Et2O. After washing, the solid was dried up under vacuum to get 1 as a black solid. 1H NMR (400 MHz, d8-THF): δ 1.76 (s, 36H, CH2), 3.60 (s, 36H, CH2), 7.12 (br, 32H, CH). 13C NMR spectra were not collected because 1 was extremely insoluble in C6D6 and d8toluene, and only slightly soluble in d8-THF. Recrystallization of 1 from THF solvent at −20 °C gave crystals suitable for X-ray analysis. Synthesis of Compounds 2−4. To a THF solution of 9-fluorenol (91 mg, 0.5 mmol) in a 25 mL Schlenk tube, Ca[N(SiMe3)2]2(Et2O)1/2 (198 mg, 0.5 mmol) was added. The reaction mixture became black immediately and was stirred at room temperature for 1 h. RCOCl (2 equiv or 1 equiv accordingly) was added at −78 °C, and the reaction mixture can be elevated to room temperature. If 1 equiv of RCOCl was used, the reaction solution should be quenched with water after stirring at room temperature for 0.5 h. After workup, the residue was purified by column chromatography to give products 2−4. 2a. White solid, isolated yield 78% (0.39 mmol, 104 mg). 1H NMR (400 MHz, CDCl3, SiMe4): δ 1.82 (s, 3H, CH3), 2.16 (s, 3H, CH3), 7.30−7.34 (m, 2H, CH), 7.44−7.48 (m, 2H, CH), 7.70−7.72 (m, 4H, CH); 13C NMR (100 MHz, CDCl3, SiMe4): δ 21.12, 26.32, 91.20, 120.30, 126.83, 128.50, 130.39, 141.14, 141.65, 142.05, 170.68, 200.83; HRMS calcd for C17H14O3Na [M + Na]+: 289.0835, found 289.0839. 2b. White solid, isolated yield 26% (0.13 mmol, 46 mg). 1H NMR (400 MHz, CDCl3, SiMe4): δ 0.84 (s, 9H, CMe3), 1.22 (s, 9H, CMe3), 7.30 (t, J = 7.6 Hz, 2H, CH), 7.45 (t, J = 7.6 Hz, 2H, CH), 7.69 (dd, J = 7.6 Hz, 2.0 Hz, 4H, CH); 13C NMR (100 MHz, CDCl3, SiMe4): δ 27.14, 27.20, 38.96, 45.08, 91.47, 120.24, 127.40, 128.13, 130.13, 1342

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Organometallics

91.39, 119.49, 123.80, 127.29, 139.02, 141.20, 151.62, 170.64, 201.32. HRMS calcd for C25H30O3Na [M + Na]+: 401.2087, found 401.2085. 18c. (0.4 mmol scale), pale yellow solid, isolated yield 74% (0.30 mmol, 126 mg). 1H NMR (400 MHz, CDCl3, SiMe4): δ 1.88 (s, 3H, CH3), 2.19 (s, 3H, CH3), 7.55 (d, J = 8.4 Hz, 2H, CH), 7.61 (dd, J = 8.0 Hz, 1.6 Hz, 2H, CH), 7.85 (d, J = 1.6 Hz, 2H, CH); 13C NMR (100 MHz, CDCl3, SiMe4): δ 20.98, 26.49, 90.23, 121.64, 122.59, 130.08, 133.71, 139.53, 142.70, 170.55, 199.45. HRMS calcd for C17H12O3Br2Na [M + Na]+: 444.9045, found 444.9043. 19a. Pale yellow solid, isolated yield 65% (0.32 mmol, 122 mg). 1H NMR (400 MHz, CDCl3, SiMe4): δ 2.34 (s, 1H, OH), 2.84 (d, J = 7.2 Hz, 2H, CH2), 4.94−4.97 (m, 2H, CH2), 5.61−5.68 (m, 1H, CH), 7.30−7.43 (m, 6H, CH), 7.54 (dd, J = 7.6 Hz, 1.6 Hz, 2H, CH), 7.59 (d, J = 7.6 Hz, 6H, CH), 7.73 (d, J = 1.2 Hz, 2H, CH); 13C NMR (100 MHz, CDCl3, SiMe4): δ 44.23, 81.54, 119.02, 120.26, 122.60, 127.03, 127.34, 127.99, 128.80, 132.62, 138.14, 140.83, 140.94, 149.27. HRMS calcd for C28H22ONa [M + Na]+: 397.1563, found 397.1558. 19b. Pale solid, isolated yield 85% (0.42 mmol, 142 mg). 1H NMR (400 MHz, CDCl3, SiMe4): δ 1.35 (s, 18H, CMe3), 2.17 (s, 1H, OH), 2.77 (d, J = 7.2 Hz, 2H, CH2), 4.90−4.96 (m, 2H, CH2), 5.61−5.72 (m, 1H, CH), 7.34 (dd, J = 7.6 Hz, 1.6 Hz, 2H, CH), 7.45 (d, J = 8.0 Hz, 2H, CH), 7.54 (d, J = 1.6 Hz, 2H, CH); 13C NMR (100 MHz, CDCl3, SiMe4): δ 31.51, 34.93, 44.36, 81.66, 118.49, 119.13, 120.84, 125.72, 133.11, 136.67, 148.35, 150.68. HRMS calcd for C24H30ONa [M + Na]+: 357.2189, found 357.2187. 19c. Pale yellow solid, isolated yield 71% (0.35 mmol, 108 mg). 1H NMR (400 MHz, CDCl3, SiMe4): δ 2.20 (s, 1H, OH), 2.78 (d, J = 7.2 Hz, 2H, CH2), 4.99−5.04 (m, 2H, CH2), 5.51−5.62 (m, 1H, CH), 7.44 (d, J = 8.0 Hz, 2H, CH), 7.50 (dd, J = 8.0 Hz, 1.6 Hz, 2H, CH), 7.64 (d, J = 1.6 Hz, 2H, CH); 13C NMR (100 MHz, CDCl3, SiMe4): δ 43.94, 81.27, 119.82, 121.36, 122.00, 127.35, 131.51, 132.23, 137.24, 149.92. 20a. White solid, isolated yield 61% (0.30 mmol, 145 mg). 1H NMR (400 MHz, CDCl3, SiMe4): δ −0.16 (s, 9H, SiMe3), −0.09 (s, 9H, SiMe3), 7.32−7.48 (m, 6H, CH), 7.59 (dd, J = 7.6 Hz, 1.6 Hz, 2H, CH), 7.68 (d, J = 7.6 Hz, 4H, CH), 7.76−7.79 (m, 4H, CH); 13C NMR (100 MHz, CDCl3, SiMe4): δ −4.45, 2.01, 82.27, 120.23, 122.78, 126.09, 127.08, 127.14, 128.84, 137.03, 139.23, 141.55, 149.63. HRMS calcd for C31H34OSi2 [M]+: 478.2143, found 478.2153. 20b. White solid, isolated yield 82% (0.41 mmol, 180 mg). 1H NMR (400 MHz, CDCl3, SiMe4): δ −0.26 (s, 9H, SiMe3), −0.18 (s, 9H, SiMe3), 1.37 (s, 18H, CMe3), 7.31 (dd, J = 8.0 Hz, 2.0 Hz, 2H, CH), 7.50 (d, J = 1.6 Hz, 2H, CH), 7.57 (d, J = 8.0 Hz, 2H, CH); 13C NMR (100 MHz, CDCl3, SiMe4): δ −4.62, 1.84, 31.57, 34.80, 81.91, 118.93, 121.56, 123.40, 135.64, 148.56, 148.89. HRMS calcd for C27H43OSi2 [M + H]+: 439.2847, found 439.2846.

h and workup, the residue was purified by column chromatography to give products 9−13. 13. White solid, isolated yield 67% (0.34 mmol, 110 mg). 1H NMR (400 MHz, CDCl3, SiMe4): δ −0.25 (s, 9H, SiMe3), δ −0.17 (s, 9H, SiMe3), 7.24−7.33 (m, 4H, CH), 7.50 (d, J = 7.2 Hz, 2H, CH), 7.70 (d, J = 7.6 Hz, 2H, CH); 13C NMR (100 MHz, CDCl3, SiMe4): δ −4.65, 1.81, 82.15, 119.83, 124.21, 126.24, 126.69, 138.11, 148.66. HRMS calcd for C19H26OSi2Na [M + Na]+: 349.1414, found 349.1398. Synthesis of Compounds 14 and 15. To a THF solution of 9fluorenol (91 mg, 0.5 mmol) in a 25 mL Schlenk tube, Ca[N(SiMe3)2]2(Et2O)1/2 (198 mg, 0.5 mmol) was added. The reaction mixture became black immediately and was stirred at room temperature for 1 h. AllylBr (61 mg, 0.5 mmol) was added at −78 °C, and the reaction mixture can be elevated to room temperature. After the reaction mixture was stirred at room temperature for 0.5 h, MeCOCl (40 mg, 0.5 mmol) or Me3SiCl (55 mg, 0.5 mmol) was added. After another 1 h and workup, the residue was purified by column chromatography to give products 14 and 15. 14. Colorless solid, isolated yield 69% (0.34 mmol, 84 mg). 1H NMR (400 MHz, CDCl3, SiMe4): δ 1.95 (s, 3H, CH3), 2.90 (d, J = 6.8 Hz, 2H, CH2), 4.87−4.93 (m, 2H, CH2), 5.48−5.55 (m, 1H, CH), 7.23−7.27 (m, 2H, CH), 7.32−7.36 (m, 2H, CH), 7.43 (d, J = 7.2 Hz, 2H, CH), 7.63 (d, J = 7.6 Hz, 2H, CH). 13C NMR (100 MHz, CDCl3, SiMe4): δ 21.63, 43.35, 86.82, 119.22, 120.03, 123.17, 127.50, 128.81, 131.49, 139.99, 145.17, 168.58. HRMS calcd for C18H16O2Na [M + Na]+: 287.1042, found 287.1039. 15. Colorless oil, isolated yield 75% (0.38 mmol, 110 mg). 1H NMR (400 MHz, CDCl3, SiMe4): δ −0.35 (s, 9H, SiMe3), 2.79 (d, J = 7.2 Hz, 2H, CH2), 4.79−4.84 (m, 2H, CH2), 5.48−5.57 (m, 1H, CH), 7.23−7.27 (m, 2H, CH), 7.30−7.34 (m, 2H, CH), 7.48 (d, J = 7.2 Hz, 2H, CH), 7.58 (d, J = 7.6 Hz, 2H, CH). 13C NMR (100 MHz, CDCl3, SiMe4): δ 1.31, 46.62, 83.17, 117.81, 119.70, 124.56, 127.37, 128.60, 133.23, 139.49, 148.49. Procedure for the Reactions of Complexes 1-R with Electrophiles. To a THF solution of substituted 9-fluorenol 16 (0.5 mmol) in a 25 mL Schlenk tube, Ca[N(SiMe3)2]2(Et2O)1/2 (198 mg, 0.5 mmol) was added. The reaction mixture became black immediately and was stirred at room temperature for 1 h. The electrophile was added at −78 °C, and the reaction mixture can be elevated to room temperature. After stirring at room temperature for 1 h and workup, the residue was purified by column chromatography to give products 17−20. 17a. Pale yellow solid, isolated yield 70% (0.35 mmol, 146 mg). 1H NMR (400 MHz, CDCl3, SiMe4): δ 0.86 (s, 9H, CMe3), 5.71 (s, 1H, OH), 7.34−7.38 (m, 2H, CH), 7.46 (t, J = 7.6 Hz, 4H, CH), 7.50 (d, J = 1.2 Hz, 2H, CH), 7.61 (d, J = 7.2 Hz, 4H, CH), 7.70 (dd, J = 8.0 Hz, 1.6 Hz, 2H, CH), 7.78 (d, J = 8.0 Hz, 2H, CH); 13C NMR (100 MHz, CDCl3, SiMe4): δ 28.23, 44.68, 87.10, 120.98, 123.12, 127.04, 127.59, 128.87, 140.56, 140.82, 141.38, 145.75, 214.85. HRMS calcd for C30H26O2Na [M + Na]+: 441.1825, found 441.1818. 17b. Pale solid, isolated yield 76% (0.38 mmol, 125 mg). 1H NMR (400 MHz, CDCl3, SiMe4): δ 0.75 (s, 9H, CMe3), 1.32 (s, 18H, CMe3), 5.56 (s, 1H, OH), 7.24 (d, J = 1.2 Hz, 2H, CH), 7.43 (dd, J = 8.0 Hz, 2.0 Hz, 2H, CH), 7.57 (d, J = 8.0 Hz, 2H, CH); 13C NMR (100 MHz, CDCl3, SiMe4): δ 28.10, 31.41, 34.92, 44.38, 87.11, 119.84, 121.51, 126.55, 139.44, 144.50, 151.24, 215.59. HRMS calcd for C26H34O2Na [M + Na]+: 401.2451, found 401.2450. 18a. Pale yellow solid, isolated yield 65% (0.32 mmol, 135 mg). 1H NMR (400 MHz, CDCl3, SiMe4): δ 1.92 (s, 3H, CH3), 2.20 (s, 3H, CH3), 7.35−7.39 (m, 2H, CH), 7.46 (t, J = 7.6 Hz, 4H, CH), 7.63− 7.66 (m, 4H, CH), 7.73 (dd, J = 8.0 Hz, 1.6 Hz, 2H, CH), 7.79 (d, J = 8.0 Hz, 2H, CH), 7.98 (d, J = 1.6 Hz, 2H, CH); 13C NMR (100 MHz, CDCl3, SiMe4): δ 21.17, 26.57, 91.12, 120.67, 125.52, 127.10, 127.68, 128.88, 129.34, 140.32, 140.37, 141.64, 142.12, 170.73, 200.70. HRMS calcd for C29H22O3Na [M + Na]+: 441.1461, found 441.1457. 18b. Pale solid, isolated yield 82% (0.41 mmol, 155 mg). 1H NMR (400 MHz, CDCl3, SiMe4): δ 1.34 (s, 18H, CMe3), 1.79 (s, 3H, CH3), 2.16 (s, 3H, CH3), 7.46−7.48 (m, 2H, CH), 7.56−7.74 (m, 4H, CH); 13 C NMR (100 MHz, CDCl3, SiMe4): δ 21.22, 26.44, 31.44, 35.04,

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ASSOCIATED CONTENT

S Supporting Information *

Crystallographic data for 1 and 6a, NMR data, further experimental details, and spectra for all new compounds. This material is available free of charge via the Internet at http:// pubs.acs.org.

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AUTHOR INFORMATION

Corresponding Authors

*E-mail: [email protected] (W.-X.Z.). *E-mail: [email protected] (Z.X.). Notes

The authors declare no competing financial interest.

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ACKNOWLEDGMENTS This work was supported by the 973 Program (2011CB808700) and the Natural Science Foundation of China (NSFC). 1343

DOI: 10.1021/acs.organomet.5b00059 Organometallics 2015, 34, 1339−1344

Article

Organometallics

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DOI: 10.1021/acs.organomet.5b00059 Organometallics 2015, 34, 1339−1344