Article pubs.acs.org/Organometallics
1,2-Addition or Enolization? Variable Reactivity of a Cerium Acetylide Complex toward Carbonyl Compounds Jee Eon Kim, Alexander V. Zabula, Patrick J. Carroll, and Eric J. Schelter* P. Roy and Diana T. Vagelos Laboratories, Department of Chemistry, University of Pennsylvania, 231 South 34th Street, Philadelphia, Pennsylvania 19104, United States S Supporting Information *
ABSTRACT: The reactions of the cerium alkyne complex bearing 2,6-bis(dimethylamino)-4-methylphenolate supporting ligands (bdmmp) and a terminal acetylide moiety, Na[Ce(C CPh)(bdmmp)3] (1), with benzaldehyde and a family of enolizable ketones led to different products depending on the acidity of the parent carbonyl compound. The reactions of 1 with benzaldehyde, acetone, benzylideneacetone, or 1,1diphenylacetone (pKaDMSO = 26.5−19.4) gave the products of nucleophilic addition of type Na[Ce(O-CR2-CCPh)(bdmmp)3] featuring a new C−C bond. In contrast, the reaction of 1 with β-tetralone (pKaDMSO = 17.6) resulted in the enolization and deprotonation of β-tetralone with subsequent replacement of the acetylide ligand at the cerium ion by the enolate. Molecular structures for the cerium products were determined by X-ray diffraction studies, providing valuable information about the performance of organocerium reagents.
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numerous natural products including (−)-atropabyssomicin8 and (−)-menthone,9 the active organocerium species “RCeCl2” have not been resolved due to their instability and difficulty in isolation. The scarcity of structural information about organocerium compounds featuring Ce−C σ-bonds10 precludes a comprehensive understanding of their reactivity, selectivity, and functional group tolerance. Recently, we employed a flexible polydentate ligand framework, 2,6-bis(dimethylamino)-4-methylphenolate (bdmmp−),11 for investigation of the impact of the substituents on the solution dynamics and redox properties in a series of cerium-bdmmp aryloxides.12 We also use the bdmmp framework in the stabilization, isolation, and structural characterization of the first thermally stable terminal trivalent cerium acetylide, Na[Ce(CCPh)(bdmmp)3] (1, Scheme 1).13 It was shown that the reaction of complex 1 with acetophenone (pKaDMSO = 24.7) resulted in the formation of a propargylic alkoxide coordinated to the cerium(III) cation, Na[Ce(OC(Me)(Ph)CCPh)(bdmmp)3] (2). The integrity of the NaCe-bdmmp system in 2 was retained according to an X-ray diffraction study. Conversely, a different type of reactivity was reported for the cerium(III) Cp*2Ce(CH(SiMe3)2) (Cp* = 1,2,3,4,5-pentamethylcyclopentadienide) complex with acetone: the corresponding reaction led to an intermediate with the enolate (−OC(Me)CH2) group coordinated to the Ce3+ cation. This intermediate further reacted with a second equivalent of acetone to form a new C−C bond through an aldol condensation.14 Interestingly, the uranium terminal alkyne complex Tp*2U(CCPh) (Tp* = bis(hydrotris(3,5-dimethyl-
INTRODUCTION Nucleophilic addition to carbonyl compounds with the formation of new C−C bonds is one of the most wellestablished synthetic strategies for the preparation and functionalization of a variety of organic compounds, ranging from industrially important simple molecules to sophisticated natural products.1 Among numerous synthetic reagents used for this addition, organometallic reagents, mainly organolithiums2 and Grignard reagents,3 play a central role in synthetic organic chemistry. Organometallic derivatives of f-block elements represent a relatively new and prospective class of “soft” reagents, particularly, for the formation of C−C bonds.4 Employing the lanthanide metal cations for carbonyl addition reactions is advantageous because of their strong Lewis acidity. The interaction of Ln3+ with the CO group enhances the electrophilicity of the carbonyl carbon, thus increasing its susceptibility to nucleophilic addition.5 Moreover, lanthanide alkyls can be used as milder, and therefore more selective, nucleophiles compared to alkyllithiums or Grignard reagents. Organocerium compounds were first applied for carbonyl addition reactions by Imamoto and co-workers for the conversion of ketones into tertiary alcohols in 1982.6 Since then, organocerium reagents, CeCl3/(RLi or RMgX), have found a wide application in organic synthesis as prospective reagents for the formation of C−H and C−C bonds in various addition reactions where the “classical” organometallic reagents failed.7 A remarkable aspect of the application of organocerium reagents is their selective 1,2-addition in reactions with highly enolizable ketones.7i Although there have been many applications of organocerium reagents for the preparation of organic compounds and © 2016 American Chemical Society
Received: April 12, 2016 Published: June 6, 2016 2086
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Organometallics
exhibit a distinctive νCC absorbance because of the weakness of the corresponding signal (see Supporting Information for the IR spectra). The νCC stretching frequency observed for 3 is higher compared to phenylacetylene (νCC = 2110 cm−1) and lower than that measured in the phenylacetylide-uranium complex Tp*2U(CCPh) (2049 cm−1).15 It should be noted that treating 3−6 with an excess of phenylacetylene did not produced complex 1. Thus, a catalytic cycle for the nucleophilic addition of a carbonyl compound to 1 cannot be closed in this case. An X-ray diffraction study for 3 showed that three bdmmp− ligands retained interactions with the sodium and cerium(III) cations in the solid state (Figure 1). In contrast, the
Scheme 1. Carbonyl Addition Reaction for Complex 1 and Acetophenone
pyrazolyl)borate)) reportedly reacted with acetone exclusively with the formation of the enolate complex Tp*2U(OC(CH3)CH2),15 whereas the reaction of ketones with another organouranium complex, U(CH2Ph)4, gave the product of the nucleophilic addition of benzyl groups to the CO bonds.16 Inspired by the remarkable thermal stability and prospective reactivity of our cerium acetylide complex 1, we have broadened the types of carbonyl substrates used for the addition reactions in this report. Moreover, we have estimated the correlation between the acidity of carbonyl compounds and their reactivity toward 1. Additionally, we report the structures for new cerium(III) alkoxide compounds that can be considered as final products in nucleophilic addition reactions.
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RESULTS AND DISCUSSION The parent acetylide complex 1 was synthesized through a metathesis reaction between Na[Ce(OTf)(bdmmp)3] and Na(CCPh) as described previously.13 The reactions of complex 1 with one equivalent of benzaldehyde or various ketones including acetone (pKaDMSO = 26.5),17 benzylideneacetone (pKaDMSO = 21.5),18 and 1,1-diphenylacetone (pKaDMSO = 19.4)19 in diethyl ether for 12 h at ambient conditions resulted in the nucleophilic addition products to the CO bond of the parent carbonyl compounds (3−6, Scheme 2). 1H NMR spectra for the crude reaction mixtures showed the formation of 3−6 as the major products. Recrystallization of crude complexes 3−6 from n-pentane solutions at −35 °C gave pure colorless solids in yields up to 72%. 1H NMR spectra of the cerium(III) complexes 3−6 show broadened and paramagnetically shifted resonances in the range from δ = 24.10 ppm to δ = −29.28 ppm (see Supporting Information for the 1 H NMR spectra). A low-intensity νCC absorbance band at 2200 cm−1 was observed in the IR spectrum of compound 3, whereas the IR investigations for complexes 4−6 did not
Figure 1. Thermal ellipsoid plot of 3 at the 30% probability level. Hydrogen atoms and minor disorder components are omitted for clarity. Methyl groups at the N atoms are depicted using a wire model.
decoordination of one of the N-donor functionalities from the sodium cation was observed in the structure of the related complex 2 (Scheme 1). The alkoxide −OC(H)(Ph)(CCPh) moiety in 3 was coordinated to the apical position at the Ce(1) coordination sphere. The corresponding Ce(1)−O(4) bond length (2.268(3) Å) was notably shortened compared to Ce(1)−Obdmmp bond distances (2.3485(13)−2.3690(13) Å) and is consistent with those reported for the CeIII alkoxide bond distances (Table 1).12,14,20 The short C(41)−C(42) distance (1.184(10) Å) is consistent with the triple bond being retained at the former phenylacetylene fragment. Surprisingly, complex 1 exhibits different reactivity toward acetone compared to the related uranium complex with a
Scheme 2. Carbonyl Addition Reactions of 1 with Benzaldehyde and Ketones with pKaDMSO = 26.5−19.4
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Organometallics Table 1. Selected Geometrical Parameters (in Å and deg) for 1−5
terminal acetylide unit, Tp*2U(CCPh), which induces the enolization of the ketone.15 In contrast, the treatment of acetone (pKaDMSO = 26.5) with complex 1 yielded the product of nucleophilic addition, 4, according to X-ray diffraction analysis (Figure 2). Key geometrical parameters for the adduct 4 are summarized in Table 1.
Figure 3. Thermal ellipsoid plots of 5 at the 30% probability level. Hydrogen atoms are omitted for clarity. Methyl groups at the nitrogen atoms are depicted using a wire model.
The X−C(40)−Y angles measured in 3−5 span from 105.0(11)° to 112.7(3)°, which indicated the sp3-hybridization of the C(40) atom, affected by nucleophilic attack. An increase in the steric demand of the alkoxide groups attached to the NaCe-bdmmp ligand framework resulted in a slight elongation of the Ce(1)−O(4) and C(40)−O(4) bond distances (Table 1). Complexes 1−5 feature various distance ranges for dative M−N or M−O interactions that show the structural and coordination nonrigidity of the NaCe-bdmmp moiety. The flexibility of the NaCe-bdmmp moiety allows for changing its geometry to satisfy both the steric and electronic demands of an additional group attached to the apical position. We found that employing a more acidic ketone, β-tetralone (pKaDMSO = 17.6),21 in the reaction with 1 led to the elimination of phenylacetylene and formation of the enolized product 7 in a high yield of 88% (Scheme 3). The molecular structure of 7 in the solid state was revealed by an X-ray diffraction study (Figure 4). The interatomic C(40)−C(41) distance (1.316(6) Å) indicated the formation of a CC bond in the β-tetralone moiety; thus, the phenylacetylide evidently eliminated one of the α-protons at C(41). Additionally, the Y−C(40)−X angles (116.5(4)− 122.6(5)°) also supported the sp2 trigonal planar geometry at
Figure 2. Thermal ellipsoid plot of 4 at the 30% probability level. Hydrogen atoms are omitted for clarity. Methyl groups at the nitrogen atoms are depicted using a wire model.
The reaction of 1 with a more acidic ketone, benzylideneacetone (pKaDMSO = 21.5), also gave a similar product of C−C coupling according to the X-ray diffraction study (5, Figure 3). The persistence of the double bond C(49)−C(50) (1.326(6) Å) in product 5 demonstrates selectivity of the organocerium complex 1 in the 1,2-addition reaction of an unsaturated carbonyl compound over 1,4-addition. Such reactivity underlies a high tolerance of organocerium reagents to alkene functional groups. The product of the reaction between complex 1 and 1,1diphenylacetone (pKaDMSO = 19.4) resulted in the nucleophilic addition of the acetylide moiety to a carbonyl group with the formation of complex 6. The NMR study for the crude reaction mixture demonstrated the presence of 6 as the major product. Multiple crystallization trials for 6 did not give suitable single crystals for X-ray diffraction study. 2088
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Organometallics Scheme 3. Reaction of 1 with β-Tetralone
and selectivity as well as their practical application in organic synthesis.
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EXPERIMENTAL SECTION
General Methods. All reactions and manipulations were performed under an inert atmosphere (N2) using standard Schlenk techniques or in a Vacuum Atmospheres, Inc., Nexus II drybox equipped with a molecular sieves 13X/Q5 Cu-0226S catalyst purifier system. Glassware was oven-dried overnight at 150 °C prior to use. 1H NMR spectra were obtained on a Bruker DMX-300 Fourier transform NMR spectrometer operating at a 1H frequency of 300 MHz. Chemical shifts were recorded in units of parts per million and referenced against residual proteo solvent peaks. Paramagnetic broadening of the resonance signals in 1H NMR spectra of 3−7 precludes the accurate integration of their intensities. The infrared spectra were measured on a PerkinElmer 1600 Series infrared spectrometer. Elemental analyses were performed at the University of California, Berkeley, Microanalytical Facility, using a PerkinElmer Series II 2400 CHNS analyzer or at Complete Analysis Laboratories, Inc. (Parsippany, NJ, USA), using a Carlo Erba EA 1108 analyzer. Materials. Diethyl ether and n-pentane were purchased from Fisher Scientific. The solvents were dried using a two-column solvent purification system comprising columns packed with Q5 reactant and neutral alumina, respectively (for n-pentane), or two columns of neutral alumina (for diethyl ether). C6D6 and toluene-d8 were purchased from Cambridge Isotope Laboratories, Inc., and stored over potassium mirror overnight prior to use. Na[Ce(CCPh)(bdmmp)3] (1) was prepared according to the literature procedure.13 β-Tetralone was purchased from Sigma-Aldrich. Anhydrous acetone (extra dry, 99.8%) was purchased from Acros Organics and used as received. Benzaldehyde and β-tetralone were distilled in an inert atmosphere and dried over molecular sieves prior to use. Benzylideneacetone and 1,1-diphenylacetone were doubly recrystallized from concentrated hexane solutions in the glovebox prior to use. General Procedure for the Synthesis of 3−6. A 20 mL scintillation vial was charged with 1 (70.0 mg, 0.0754 mmol, 1 equiv), diethyl ether (2 mL), and a Teflon-coated stir bar. Anhydrous carbonyl substrate (1 equiv) was added to the vial using a micropipet or after dissolving in diethyl ether (1 mL). The reaction mixture was stirred at room temperature for 14 h with the formation of a yellow-orange solution. The volatiles were then removed under reduced pressure. The resulting crude yellow-orange residue was suspended in 5 mL of n-pentane and filtered through a plug of Celite. The solid residue was subsequently rinsed with 2 × 2 mL of n-pentane, and an additional ∼3 mL of n-pentane was then added to the combined organic fraction. The evaporation of this solution to ∼1 mL under reduced pressure followed by storage at −35 °C for 12 h gave colorless crystals of the product. Data for 3. Yield: 56.1 mg (0.0542 mmol, 72% yield). 1H NMR (300 MHz, C6D6) δ: 23.30 (br), 11.70 (br), 10.50, 10.30, 9.40, 8.28, 7.82/7.58 (overlapping), 4.88 (br), 3.51, 2.24, 2.06, 1.42, 1.22, 1.06, 0.94, 0.88, 0.32, −10.58/−12.64 (br, overlapping), −19.36 (br). IR (THF, cm−1) ν: 2200. Anal. Calcd for C54H74CeN6NaO4: C, 62.71; H, 7.21; N, 8.13. Found: C, 62.46; H, 7.17; N, 8.22. Data for 4. Yield: 40.0 mg (0.0406 mmol, 54% yield). 1H NMR (300 MHz, C6D6) δ: 24.10 (br), 12.20, 10.40, 9.06, 7.80, 7.39, 6.86, 6.12, 5.63, 5.11, 4.65, 4.27, 4.09, 3.83, 3.74, 3.56, 3.33, 2.85, 2.73, 1.94, 1.51, 1.37, 1.23, 0.86, −12.3 (br). Anal. Calcd for C50H74CeN6NaO4: C, 60.89; H, 7.56; N, 8.52. Found: C, 60.80; H, 7.47; N, 8.41. Data for 5. Yield: 38.3 mg (0.0357 mmol, 47%). 1H NMR (300 MHz, C6D6) δ: 23.89, 20.16, 14.33, 12.40, 11.02, 9.91, 9.12, 8.93, 8.58, 8.48, 8.27, 8.02, 7.68, 7.53, 7.38, 6.94, 4.91, 4.61, 1.65, 1.36, 1.31, 1.30, 1.28, 1.26, 1.24, 1.22, 1.19, 1.05, 0.92, 0.89, 0.88, 0.86, −11.64, −17.94. Anal. Calcd for C57H78CeN6NaO4: C, 63.72; H, 7.32; N, 7.82. Found: C, 63.42; H, 7.51; N, 7.50. Data for 6. Yield: 17.3 mg (0.0152 mmol, 20%). 1H NMR (300 MHz, toluene-d8) δ: 17.37, 16.01, 14.96, 13.75, 12.29, 10.57, 7.79, 6.46, 6.35, 5.70, 5.26, 4.77, 4.67, 3.64, 2.09, 1.88, 1.71, 1.34, 0.87, 0.28, −3.63, −5.15, −19.74, −23.27, −29.28. Anal. Calcd for
Figure 4. Thermal ellipsoid plot for 7 at the 30% probability level. Only hydrogen atoms at C(48) and C(49) atoms are shown. Minor disorder components are not shown. Methyl groups at the nitrogen atoms are depicted using a wire model. Selected bond distances (Å) and angles (deg): Ce(1)−O(1) 2.290(3), Ce(1)−O(2) 2.370(3), Ce(1)−O(3) 2.326(2), Ce(1)−O(4) 2.318(3), C(40)−O(4) 1.333(5), C(40)−C(41) 1.316(6), C(40)−C(49) 1.524(7); C(41)− C(40)−O(4) 122.6(5), O(4)−C(40)−C(49) 116.5(4), C(41)− C(40)−C(49) 119.7(5).
C(40). The bond lengths for C(40)−O(4) and C(40)−C(41) were 1.333(5) and 1.316(6) Å, respectively, supporting that a negative charge was mainly localized on the C(40)−O(4) bond. These bonding metrics were consistent with the previously reported κ1-bonded metal−enolate bond in Cp2Zr(NHtBu)(OCCH(CH2)3CH(CCH3)3.22
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CONCLUSION In summary, we have investigated the reactivity of a stable terminal cerium acetylide complex bearing the fluxional NaCebdmmp ligand framework toward benzaldehyde and ketones showing variable acidity of the α-protons (pKaDMSO = 26.5− 17.6). No evidence of enolization products was detected in the reactions with insertion of acetone, acetophenone, benzylideneacetone, and 1,1-diphenylacetone. Instead, the C−C bond formation upon the nucleophilic addition of phenylacetylide to the carbonyl group was observed. However, the reaction of 1 with the more acidic β-tetralone (pKaDMSO = 17.6)21 exclusively produced the enolate complex 7. The structural investigations for new products revealed the persistence and integrity of the NaCe-bdmmp core upon binding with various ligands. The results provided here are useful for the structural description of organocerium(III) compounds, understanding their reactivity 2089
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Compounds, Part 1; Rapport, Z.; Marek, I., Eds.; John Wiley & Sons Ltd: Chichester, England, 2004. (c) The Chemistry of Organolithium Compounds, Part 2; Rapport, Z.; Marek, I., Eds.; John Wiley & Sons Ltd: Chichester, England, 2006. (d) Wu, G.; Huang, M. Chem. Rev. 2006, 106, 2596−2616. (3) (a) The Chemistry of Organomagnesium Compounds; Rapport, Z.; Marek, I., Eds.; John Wiley & Sons Ltd: Chichester, England, 2008. (b) Hatano, M.; Ishihara, K. Synthesis 2008, 11, 1647−1675. (c) Luderer, M. R.; Bailey, W. F.; Luderer, M. R.; Fair, J. D.; Dancer, R. J.; Sommer, M. B. Tetrahedron: Asymmetry 2009, 20, 981− 998. (d) Trost, B. M.; Weiss, A. H. Adv. Synth. Catal. 2009, 351, 963− 983. (e) Zong, H.; Huang, H.; Liu, J.; Bian, G.; Song, L. J. Org. Chem. 2012, 77, 4645−4652. (4) (a) Molander, G. A. Chem. Rev. 1992, 92, 29−68. (b) Kobayashi, S.; Sugiura, M.; Kitagawa, H.; Lam, W. W.-L. Chem. Rev. 2002, 102, 2227−2302. (c) Krasovskiy, A.; Kopp, F.; Knochel, P. Angew. Chem., Int. Ed. 2006, 45, 497−500. (5) Marcantoni, E.; Petrini, M. Comprehensive Organic Synthesis II 2014, 1, 344−364. (6) (a) Imamoto, T.; Kusumoto, T.; Yokoyama, M. J. Chem. Soc., Chem. Commun. 1982, 1042−1044. (b) Imamoto, T.; Sugiura, Y.; Takiyama, N. Tetrahedron Lett. 1984, 25, 4233−4236. (c) Imamoto, T.; Takiyama, N.; Nakamura, K.; Hatajima, T.; Kamiya, Y. J. Am. Chem. Soc. 1989, 111, 4392−4398. (7) (a) Greeves, N.; Lyford, L. Tetrahedron Lett. 1992, 33, 4759− 4760. (b) Jung, P. M. J.; Burger, A.; Biellmann, J.-F. Tetrahedron Lett. 1995, 36, 1031−1034. (c) Evans, W. J.; Feldman, J. D.; Ziller, J. W. J. Am. Chem. Soc. 1996, 118, 4581−4584. (d) Dimitrov, V.; Kostova, K.; Genov, M. Tetrahedron Lett. 1996, 37, 6787−6790. (e) Matsukawa, S.; Funabashi, Y.; Imamoto, T. Tetrahedron Lett. 2003, 44, 1007−1010. (f) Conlon, D. A.; Kumke, D.; Moeder, C.; Hardiman, M.; Hutson, G.; Sailer, L. Adv. Synth. Catal. 2004, 346, 1307−1315. (g) Krasovskiy, A.; Knochel, P. Synthesis 2006, 2006, 890−891. (h) Metzger, A.; Gavryushin, A.; Knochel, P. Synlett 2009, 2009, 1433−1436. (i) Bartoli, G.; Marcantoni, E.; Marcolini, M.; Sambri, L. Chem. Rev. 2010, 110, 6104−6143. (j) Sadler, S.; Persons, K. S.; Jones, G. B.; Ray, R. Bioorg. Med. Chem. Lett. 2011, 21, 4638−4641. (k) Marcantoni, E.; Sambri, L. Comprehensive Organic Synthesis II 2014, 1, 267−277. (l) Guzel, M.; Watts, J.; McGilvary, M.; Wright, M.; Kiren, S. Tetrahedron Lett. 2015, 56, 5275−5277. (8) Bihelovic, F.; Karadzic, I.; Matovic, R.; Saicic, R. N. Org. Biomol. Chem. 2013, 11, 5413−5424. (9) Panev, S.; Dimitrov, V. Tetrahedron: Asymmetry 2000, 11, 1517− 1526. (10) (a) Heeres, H. J.; Meetsma, A.; Teuben, J. H.; Rogers, R. D. Organometallics 1989, 8, 2637−2646. (b) Avent, A. G.; Caro, C. F.; Hitchcock, P. B.; Lappert, M. F.; Li, Z.; Wei, X.-H. Dalton Trans. 2004, 1567−1577. (c) Maron, L.; Werkema, E. L.; Perrin, L.; Eisenstein, O.; Andersen, R. A. J. Am. Chem. Soc. 2005, 127, 279−292. (d) Hitchcock, P. B.; Huang, Q.; Lappert, M. F.; Zhou, M. Dalton Trans. 2005, 2988− 2993. (e) Wooles, A. J.; Mills, D. P.; Lewis, W.; Blake, A. J.; Liddle, S. T. Dalton Trans. 2010, 39, 500−510. (f) Occhipinti, G.; Meermann, C.; Dietrich, H. M.; Litlabø, R.; Auras, F.; Törnroos, K. W.; MaichleMössmer, C.; Jensen, V. R.; Anwander, R. J. Am. Chem. Soc. 2011, 133, 6323−6337. (g) Gregson, M.; Lu, E.; McMaster, J.; Lewis, W.; Blake, A. J.; Liddle, S. T. Angew. Chem., Int. Ed. 2013, 52, 13016−13019. (11) Hogerheide, M. P.; Ringelberg, S. N.; Grove, D. M.; Jastrzebski, J. T. B. H.; Boersma, J.; Smeets, W. J. J.; Spek, A. L.; van Koten, G. Inorg. Chem. 1996, 35, 1185−1194. (12) Kim, J. E.; Carroll, P. J.; Schelter, E. J. New J. Chem. 2015, 39, 6076−6084. (13) Kim, J. E.; Weinberger, D. S.; Carroll, P. J.; Schelter, E. J. Organometallics 2014, 33, 5948−5951. (14) Heeres, H. J.; Maters, M.; Teuben, J. H.; Helgesson, G.; Jagner, S. Organometallics 1992, 11, 350−356. (15) Matson, E. M.; Fanwick, P. E.; Bart, S. C. Organometallics 2011, 30, 5753−5762. (16) Kraft, S. J.; Fanwick, P. E.; Bart, S. C. Organometallics 2013, 32, 3279−3285.
C62H82CeN6NaO4: C, 65.41; H, 7.26; N, 7.38. Found: C, 65.28; H, 7.44; N, 7.53. Synthesis and Data for 7. A 20 mL scintillation vial was charged with 1 (78.7 mg, 0.0847 mmol, 1 equiv), diethyl ether (2 mL), and a Teflon-coated stir bar. Anhydrous β-tetralone (12.4 mg, 11.2 μL, 0.0847 mmol, 1 equiv) was added by micropipet under stirring. The reaction was stirred for 12 h, and the solvent was then removed under reduced pressure. n-Pentane (5 mL) was added to the crude product, and the resulting suspension was filtered through a plug of Celite. Evaporation of the solvent and subsequent recrystallization of the product from a saturated n-pentane solution at −35 °C gave yellow crystals of 7. Yield: 72.8 mg (0.075 mmol, 88%). 1H NMR (300 MHz, C6D6) δ: 26.95, 22.60, 12.64, 12.25, 11.46, 10.12, 9.81, 8.24, 7.39, 4.43, 1.23, 1.12, 0.90, 0.88, 0.86, 0.32, −7.94, −10.46, −17.21. Anal. Calcd for C49H72CeN6NaO4: C, 60.53; H, 7.46; N, 8.64. Found: C, 60.45; H, 7.47; N, 8.45. X-ray Crystallography. X-ray intensity data were collected on a Bruker APEXII CCD area detector employing graphite-monochromated Mo Kα radiation (λ = 0.710 73 Å) at 100(1) K. Rotation frames were integrated using SAINT,23 producing a listing of unaveraged F2 and σ(F2) values, which were then passed to the SHELXTL program package24 for further processing and structure solution. The intensity data were corrected for Lorentz and polarization effects and for absorption using SADABS.25 Structures were solved by direct methods (SHELXS-97).26 Refinement was performed by full-matrix leastsquares based on F2 using SHELXL-97.26 All of the reflections were used during refinement. Non-hydrogen atoms were refined anisotropically, and hydrogen atoms were refined using a riding model. Disorder in 3. The presence of two different stereoforms of the 1,3diphenylpropargyl unit results in a positional disorder of this group over two positions, with the major component contribution of 0.655(4). Disorder in 7. The C(27)-bdmmp group is positionally disordered over two positions, with the major component contribution refined at the fixed position of 0.6. For further crystal and data collection details see Table S1 (SI).
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ASSOCIATED CONTENT
S Supporting Information *
The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acs.organomet.6b00290. Table S1, 1H NMR and IR spectra (PDF) Crystallographic files (CIF)
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AUTHOR INFORMATION
Corresponding Author
*E-mail:
[email protected]. Notes
The authors declare no competing financial interest.
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ACKNOWLEDGMENTS E.J.S. acknowledges the University of Pennsylvania for financial support. We thank the NSF for financial support (CHE1362854) and for support of the X-ray diffractometer used in this work (CHE-0840438). We thank Prof. Christopher R. Graves (Albright College) for helpful discussions.
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REFERENCES
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