Mg-Promoted Regioselective Cross-Coupling of Stilbene Derivatives with Carbonyl Compounds

Yoshimasa Yamamoto; Seiji Kawano; Hirofumi Maekawa; Ikuzo Nishiguchi

doi:10.1055/s-2003-44970

LETTER

Mg-Promoted Regioselective Cross-Coupling of Stilbene Derivatives with Carbonyl Compounds

Yoshimasa Yamamoto, Seiji Kawano, Hirofumi Maekawa, Ikuzo Nishiguchi*
Department of Chemistry, Nagaoka University of Technology, 1603-1, Kamitomioka-cho, Nagaoka, Niigata 940-2188, Japan
Fax: +81(2)589300; e-Mail: nishiiku@vos.nagaokaut.ac.jp;

Abstract

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Abstract

Treatment of stilbene derivatives with aliphatic carbonyl compounds in the presence of trimethylsilyl chloride (TMSCl) and Mg metal in N,N-dimethylformamide (DMF) at room temperature brought about regioselective cross-coupling to give the corresponding phenethyl alcohols in moderate to good yields. These reactions may be initiated through one-electron transfer from Mg metal to the carbon-carbon double bond of stilbene derivatives to give the corresponding anion radical species, which were subjected to electrophilic attack of aliphatic carbonyl compounds followed by fast second electron transfer generating the corresponding α-benzyl anions.

Key words

electron transfer - reductions - magnesium, - cross-coupling - regioselectivity

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Referenzen

References

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10

Mg turnings for a Grignard reaction can be used without any pre-treatment.

11

The use of less than 10 equiv mol of acetone(2a) resulted in decrease in the yield of phenethyl alcohols 3a accompanying increase in formation of tarry material. Thus, the use of 3 equiv mol and 5 equiv mol of 2a provided 3a in 58% and 63% yields, respectively.

12

General Methods: Stilbene 1a, acenaphthylene (7a), aliphatic carbonyl compounds 2, TMSCl, Mg and levulinic acid esters were purchased from Aldrich Chemical Co. Ltd, Tokyo Kasei Kogyo Co. Ltd or Nacalai Tesque Ltd, and were used without further purification. The compound,
α-methylstilbene (1b) was prepared by the reaction of benzylmagnesium chloride with benzaldehyde followed by dehydration.¹³ The compound, 1-methylacenaphthylene (7b) was prepared by the reported method. [14] DMF was dried on CaH₂ and then was distilled under reduced pressure.
¹H NMR and ¹³C NMR spectra were measured by a JEOL JNM-EX-400 (400 MHz and 100 MHz) spectrometer or a JEOL JNM-GX-270 (270 MHz and 67.8 MHz) spectrometer, with TMS as an internal standard. IR spectra were measured by a JASCO IR-810 spectrometer or JASCO FT/IR-400 Plus spectrometer. Mass spectra were obtained using a Shimadzu GC-MS QP-2000A or a JEOL JMS-600H. GC analysis was conducted through a Shimadzu GC-14B with FID using a capillary column packed with DB-17. The apparatus of cyclic voltammetry was ALS MODEL 600. The apparatus of elemental analysis was Yanaco CHN CORDER MT-6. Melting point was measured by a Yanaco MP-J3.
Typical Procedure for Mg-Promoted Cross-Coupling of Stilbene Derivatives with Carbonyl Compounds is as Follows: Into a DMF (20 mL) solution containing commercially available Mg turnings (40 mmol) for Grignard reaction was added dropwise a DMF solution (40 mL) of stilbene derivatives (1 or 7, 10 mmol), TMSCl (20 mmol or 50 mmol) and carbonyl compounds (2, 100 mmol) at 5-10 °C with magnetic stirring under N₂ atmosphere during a period of 45 min. After the addition, the mixture was stirred at r.t. for additional ca 15 h. After the reaction, the reaction mixture was poured into water (300 mL) and was extracted with EtOAc (3 × 100 mL). The combined extracts are washed with sat. aq NaHCO₃ solution (3 × 50 mL), and sat. aq NaCl solution (3 × 50 mL), and then dried over anhyd MgSO₄. The solution was filtered and concentrated under reduced pressure. To the residue an EtOH solution (40 mL) containing 1% HCl (10 mL) was added, and stirred for 20 min at r.t. Then, the reaction mixture was poured into water (200 mL) and was extracted with EtOAc (3 × 100 mL). The combined extracts are washed with sat. aq NaHCO₃ (3 × 50 mL) solution, and sat. aq NaCl solution, and then dried over anhyd MgSO₄. Usual work-up and subsequent column chromatography gave the corresponding cross-coupled products 3 and 8.
All the new compounds among the products were identified by spectroscopic and elemental analysis, and others were characterized by comparison of their chromatographic and spectroscopic behaviors with those of the authentic samples, as shown below.
2-Methyl-3,4-diphenyl-2-butanol (3a) [17]
Mp 63-66 °C. IR (neat): 3420, 3020, 2970, 1600, 1490, 1450, 1370, 1150 cm^-1. ¹H NMR (270 MHz, CDCl₃): δ = 1.24 (s, 3 H), 1.26 (s, 3 H), 1.55 (s, 1 H), 2.90 (dd, J = 3.0 Hz, J = 11.6 Hz, 1 H), 3.02 (dd, J = 11.6 Hz, J = 13.4 Hz, 1 H), 3.28 (dd, J = 3.0 Hz, J = 13.4 Hz, 1 H), 6.95-7.24 (m, 10 H). ¹³C NMR (67.8 MHz, CDCl₃): δ = 27.91, 28.39, 36.16, 59.21, 72.92, 125.39, 126.43, 127.83 (2 ×), 128.69, 129.54, 140.49, 140.95. EI-MS (22 eV): m/z = 240 [M⁺]. Anal. Calcd for C₁₇H₂₀O: C, 84.96; H, 8.39. Found: C, 84.67; H, 8.62.
3-Ethyl-1,2-diphenyl-3-pentanol (3b)
IR (neat): 3460, 3030, 2960, 1600, 1500, 1460, 1380, 1130 cm^-1. ¹H NMR (270 MHz, CDCl₃): δ = 0.84 (t, J = 7.6 Hz, 3 H), 0.95(t, J = 7.6 Hz, 3 H), 1.23-1.45 (m, 3 H), 1.40 (q, J = 7.6 Hz, 2 H), 2.92-3.05 (m, 2 H), 3.18-3.22 (m, 1 H), 6.90-7.19 (m, 10 H). ¹³C NMR (67.8 MHz, CDCl₃): δ = 7.74, 8.18, 28.20, 29.38, 35.85, 54.42, 76.43, 125.28, 126.19, 127.74 (2 ×), 128.79, 129.87, 140.58, 141.08. EI-MS (20 eV): m/z = 268 [M⁺]. Anal. Calcd for C₁₉H₂₄O: C, 85.03; H, 9.01. Found: C, 85.06; H, 8.92.
1-(1,2-Diphenylethyl)cyclopentanol (3c)
Mp 40-42 °C. IR (neat): 3450, 3020, 2940, 1600, 1490, 1450, 1370, 1140 cm^-1. ¹H NMR (270 MHz, CDCl₃): δ = 1.19-1.29 (m, 2 H), 1.60-1.85 (m, 7 H), 2.92 (dd, J = 5.0 Hz, J = 9.6 Hz, 1 H), 3.11-3.21 (m, 2 H), 6.96-7.23 (m, 10 H). ¹³C NMR (67.8 MHz, CDCl₃): δ = 23.44, 23.87, 37.14, 38.84, 40.03, 57.48, 84.84, 125.40, 126.35, 127.84, 127.92, 128.74, 129.08, 140.95, 141.46. EI-MS (22 eV): m/z = 266 [M⁺]. Anal. Calcd for C₁₉H₂₂O: C, 85.67; H, 8.32. Found: C, 85.40; H, 8.22.
1-(1,2-Diphenylethyl)cyclohexanol (3d)
Mp 42-44 °C. IR (neat): 3490, 3020, 2930, 1600, 1490, 1450, 1370, 1150 cm^-1. ¹H NMR (270 MHz, CDCl₃): δ = 1.14-1.85 (m, 11 H), 2.85 (dd, J = 11.2 Hz, J = 3.0 Hz, 1 H), 3.00 (dd, J = 13.5 Hz, J = 11.2 Hz, 1 H), 3.29 (dd, J = 13.5 Hz, J = 3.0 Hz, 1 H), 6.93-7.23 (m, 10 H). ¹³C NMR (67.8 MHz, CDCl₃): δ = 21.97, 22.09, 25.76, 35.48, 35.89, 35.97, 58.56, 73.25, 125.29, 126.26, 127.75 (2 ×), 128.79, 129.73, 140.54, 141.25. EI-MS (22 eV): m/z = 280 [M⁺]. Anal. Calcd for C₂₀H₂₄O: C, 85.67; H, 8.63. Found: C, 85.64; H, 8.64.
3-Methyl-1,2-diphenyl-3-pentanol (3e)
Diastereomer ratio, 62:38. IR (neat): 3460, 3030, 2960, 1600, 1500, 1460, 1380, 1130 cm^-1. ¹H NMR (270 MHz, CDCl₃): δ (mixture of isomers) = 0.95 (t, J = 7.4 Hz, 3 H), 1.12 (s, 1.86 H, major isomer), 1.25 (s, 1.14 H, minor isomer), 1.37 (s, 1 H), 1.50-1.62 (m, 2 H), 2.87-3.31 (m, 3 H), 6.93-7.22 (m, 10 H). EI-MS (22 eV): m/z = 236 [M - H₂O]⁺. Anal. Calcd for C₁₈H₂₂O: C, 84.99; H, 8.72. Found: C, 84.86; H, 8.88.
3-Methyl-1,2-diphenyl-3-hexanol (3f)
Diastereomer ratio, 61:39. IR (neat): 3460, 3040, 2950, 1600, 1500, 1450, 1380, 1130 cm^-1. ¹H NMR (270 MHz, CDCl₃): δ (mixture of isomers) = 0.92 (m, 3 H), 1.14 (s, 1.83 H, major isomer), 1.26 (s, 1.17 H, minor isomer), 1.31-1.60 (m, 5 H), 2.87-3.06 (m, 2 H), 3.19-3.31 (m, 1 H), 6.93-7.24 (m, 10 H). EI-MS (22 eV): m/z = 268 [M⁺]. Anal. Calcd for C₁₉H₂₄O: C, 85.03; H, 9.01. Found: C, 84.95; H, 8.87.
3,4-Dimethyl-1,2-diphenyl-3-pentanol (3g)
Diastereomer ratio, 58:42; mp 68-70 °C (major isomer).
IR (neat): 3450, 3030, 2960, 1590, 1510, 1460, 1370, 1140 cm^-1. ¹H NMR (270 MHz, CDCl₃): δ (major isomer) = 0.92 (s, 3 H), 1.00 (d, J = 7.1 Hz, 3 H), 1.03 (d, J = 7.1 Hz, 3 H), 1.35 (s, 1 H), 2.09 (sept, J = 7.1 Hz, 1 H), 2.93-3.04 (m, 2 H), 3.23-3.31 (m, 1 H), 6.89-7.24 (m, 10 H). ¹H NMR (270 MHz, CDCl₃): δ (mixture of isomers) = 0.89(d, J = 6.8 Hz, 1.26 H, minor isomer), 0.92 (s, 1.74 H, major isomer), 0.95 (d, J = 6.8 Hz, 1.26 H, minor isomer), 1.00 (d, J = 7.1 Hz, 1.74 H, major isomer), 1.03 (d, J = 7.1 Hz, 1.74 H, major isomer), 1.27 (s, 1.26 H, minor isomer), 1.40 (s, 1 H), 1.60 (sept, J = 6.8 Hz, 0.42 H, minor isomer), 2.09 (sept, J = 7.1 Hz, 0.58 H, major isomer), 2.93-3.07 (m, 2 H), 3.21-3.31 (m, 1 H), 6.89-7.31 (m, 10 H). ¹³C NMR (67.8 MHz, CDCl₃): δ (major isomer) = 17.18, 17.98, 20.95, 34.13, 35.43, 55.05, 76.69, 125.29, 126.19, 127.76, 127.78, 128.85, 129.79, 141.20, 141.32. EI-MS (22 eV): m/z = 250 [M - H₂O]⁺. Anal. Calcd for C₁₉H₂₄O: C, 85.03; H, 9.01. Found: C, 85.02; H, 8.92.
3,5-Dimethyl-1,2-diphenyl-3-hexanol (3h)
Diastereomer ratio, 64:36. IR (neat): 3470, 3020, 2950, 1610, 1490, 1460, 1380, 1160 cm^-1. ¹H NMR (270 MHz, CDCl₃): δ (mixture of isomers) = 0.93-1.00 (m, 6 H), 1.18 (s, 1.92 H, major isomer), 1.25 (s, 1.08 H, minor isomer), 1.31 (s, 1 H), 1.39-1.55 (m, 2 H), 1.85-1.92 (m, 1 H),
2.85-3.05 (m, 2 H), 3.18-3.32 (m, 1 H), 6.92-7.22 (m, 10 H). EI-MS (22 eV): m/z = 264 [M - H₂O]⁺. Anal. Calcd for C₂₀H₂₆O: C, 85.06; H, 9.28. Found: C, 85.31; H, 9.02.
1,2-Diphenyl-3-hexanol (3i)
Diastereomer ratio, 61:39; mp 99-102 °C (major isomer).
IR (neat): 3380, 3040, 2910, 1590, 1500, 1450, 1360, 1140 cm^-1. ¹H NMR (270 MHz, CDCl₃): δ (major isomer) = 0.85(t, J = 6.8 Hz, 3 H), 1.23-1.57 (m, 5 H), 2.90-2.97 (m, 2 H), 3.25-3.32 (m, 1 H), 3.79-3.84 (m, 1 H), 6.97-7.26 (m, 10 H). ¹H NMR (270 MHz, CDCl₃): δ (minor isomer) = 0.85(t, J = 7.2 Hz, 3 H), 1.19-1.47 (m, 5 H), 2.86-2.99 (m, 2 H), 3.19 (dd, J = 7.2 Hz, J = 13.6 Hz, 1 H), 3.75-3.77 (m, 1 H), 7.08-7.30 (m, 10 H). ¹³C NMR (67.8 MHz, CDCl₃): δ (major isomer) = 14.05, 19.09, 37.00, 37.77, 54.51, 74.90, 125.54, 126.30, 127.88, 128.13, 128.52, 128.94, 140.44, 141.73. ¹³C NMR (67.8 MHz, CDCl₃): δ (minor isomer) = 14.02, 19.12, 37.79, 38.72, 53.32, 72.90, 125.81, 126.65, 128.13, 128.26, 129.07, 129.16, 140.48, 140.71. EI-MS (20 eV): m/z = 252 [M - 2]⁺. Anal. Calcd for C₁₈H₂₂O: C, 84.99; H, 8.72. Found: C, 84.99; H, 8.95.
1,2-Diphenyl-3-heptanol (3j)
Diastereomer ratio, 60:40; mp 75-77 °C (major isomer).
IR (neat): 3390, 3030, 2910, 1600, 1500, 1450, 1350, 1140 cm^-1. ¹H NMR (270 MHz, CDCl₃): δ (major isomer) = 0.84 (t, J = 6.9 Hz, 3 H), 1.19-1.58 (m, 7 H), 2.87-2.98 (m, 2 H), 3.25-3.36 (m, 1 H), 3.80 (m, 1 H), 6.96-7.26 (m, 10 H). [¹H NMR (270 MHz, CDCl₃): δ (mixture of isomers) = 0.81-0.88 (m, 3 H), 1.19-1.58 (m, 7 H), 2.85-3.00 (m, 2 H), 3.15-3.39 (m, 1 H), 3.80 (m, 1 H), 6.96-7.31 (m, 10 H). ¹³C NMR (67.8 MHz, CDCl₃): δ (major isomer) = 14.13, 22.65, 28.09, 34.55, 37.74, 54.47, 75.18, 125.55, 126.31, 127.90, 128.14, 128.52, 128.95, 140.45, 141.76. EI-MS (20 eV): m/z = 266 [M - 2]⁺. Anal. Calcd for C₁₉H₂₄O: C, 85.03; H, 9.01. Found: C, 84.75; H, 8.86.
4-Methyl-1,2-diphenyl-3-pentanol (3k)
Diastereomer ratio, 60:40.; mp 74-75 °C (major isomer).
IR (neat): 3380, 3010, 2900, 1610, 1500, 1450, 1380, 1140 cm^-1. ¹H NMR (270 MHz, CDCl₃): δ (major isomer) = 0.84 (d, J = 6.8 Hz, 3 H), 0.95 (d, J = 6.8 Hz, 3 H), 1.54-1.61 (m, 2 H), 2.82-2.98 (m, 2 H), 3.36-3.41 (m, 1 H), 3.64-3.70 (m, 1 H), 6.91-7.25 (m, 10 H). ¹H NMR (270 MHz, CDCl₃): δ (minor isomer) = 0.93 (d, J = 6.8 Hz, 3 H), 0.93(d, J = 6.8 Hz, 3 H), 1.28 (m, 1 H), 1.53-1.63 (m, 1 H), 2.89-3.18 (m, 3 H), 3.42 (m, 1 H), 7.05-7.30 (m, 10 H). ¹³C NMR (67.8 MHz, CDCl₃): δ (major isomer) = 15.19, 20.42, 29.95, 38.40, 52.09, 79.95, 125.47, 126.19, 127.80, 128.18, 128.38, 129.05, 140.52, 142.11. ¹³C NMR (67.8 MHz, CDCl₃): δ (minor isomer) = 7.63, 19.89, 31.12, 39.52, 50.54, 78.43, 125.72, 126.53, 128.03, 128.19, 128.97, 129.11, 140.32, 140.96. EI-MS (20 eV): m/z = 252 [M - 2]⁺. Anal. Calcd for C₁₈H₂₂O: C, 84.99; H, 8.72. Found: C, 85.20; H, 9.02.
2,3-Dimethyl-3,4-diphenyl-2-butanol (3l)
IR (neat): 3490, 3030, 2980, 1600, 1500, 1460, 1380, 1160 cm^-1. ¹H NMR(270 MHz, CDCl₃): δ = 1.09 (s, 3 H), 1.23 (s, 3 H), 1.31 (s, 3 H), 1.41 (s, 1 H), 2.90 (d, J = 13.8 Hz, 1 H), 3.72(d, J = 13.8 Hz, 1 H), 6.84-7.53 (m, 10 H). ¹³C NMR (67.8 MHz, CDCl₃): δ = 21.16, 26.31, 26.48, 40.65, 49.43, 75.62, 125.59, 126.05, 127.39, 127.48, 128.88, 130.32, 139.18, 143.41. EI-MS (22 eV): m/z = 236 [M - H₂O]⁺. Anal. Calcd for C₁₈H₂₂O: C, 84.99; H, 8.72. Found: C, 84.85; H, 8.69.
2,4-Dimethyl-1,2-diphenyl-3-pentanol (3m)
Diastereomer ratio, 55:45; mp 56-58 °C (minor isomer). ¹H NMR (270 MHz, CDCl₃): δ (minor isomer) = 0.42 (d, J = 7.0 Hz, 3 H), 0.99(d, J = 7.0 Hz, 3 H), 1.22 (s, 3 H), 1.43 (d, J = 6.8 Hz, 1 H), 1.96 (dsept, J = 2.1 Hz, J = 7.0 Hz, 1 H), 3.08(d, J = 13.2 Hz, 1 H), 3.18 (d, J = 13.2 Hz, 1 H), 3.57 (dd, J = 2.1 Hz, J = 6.8 Hz, 1 H), 6.89-7.49 (m, 10 H). ¹H NMR (270 MHz, CDCl₃): δ (mixture of isomers) = 0.42 (d, J = 7.0 Hz, 1.35 H, minor isomer), 0.74 (d, J = 6.9 Hz, 1.65 H, major isomer), 0.82 (d, J = 6.9 Hz, 1.65 H, major isomer), 0.98 (d, J = 7.0 Hz, 1.35 H, minor isomer), 1.22 (s, 1.35 H, minor isomer), 1.24 (s, 1.65 H, major isomer), 1.50 (d, J = 6.8 Hz, 0.45 H, minor isomer), 1.60 (dsept, J = 2.7 Hz, J = 6.9 Hz, 0.55 H, major isomer), 1.70 (d, J = 6.8 Hz, 0.55 H, major isomer), 1.96 (dsept, J = 2.1 Hz, J = 7.0 Hz, 0.45 H, minor isomer), 3.06-3.20 (m, 2 H), 3.57 (dd, J = 2.1 Hz, J = 6.8 Hz, 0.45 H, minor isomer), 3.89 (dd, J = 2.7 Hz, J = 6.8 Hz, 0.55 H, major isomer), 6.64-7.49 (m, 10 H). ¹³C NMR (67.8 MHz, CDCl₃): δ (minor isomer) = 16.17, 20.16, 23.97, 28.63, 45.79, 47.14, 82.33, 125.74, 126.17, 127.39, 127.70, 127.95, 130.49, 138.37, 144.15. EI-MS (22 eV): m/z = 266 [M - 2]⁺. Anal. Calcd for C₁₉H₂₄O: C, 85.03; H, 9.01. Found: C, 85.09; H, 9.11.
1-(1-Hydroxypropyl)acenaphthene (8a)
Diastereomer ratio, 64:36; mp: 59-60 °C (major isomer).
IR (neat): 3560, 3420, 3040, 2960, 2930, 2880, 1620, 1600, 1590, 1500 cm^-1. ¹H NMR (400 MHz, CDCl₃): δ (major isomer) = 1.06 (t, J = 7.4 Hz, 3 H), 1.32 (s, 1 H), 1.61-1.68 (m, 2 H), 3.36 (dd, J = 17.2 Hz, J = 7.7 Hz, 1 H), 3.42 (dd, J = 17.2 Hz, J = 4.4 Hz, 1 H), 3.82 (ddd, J = 7.7 Hz, J = 4.4 Hz, J = 2.4 Hz, 1 H), 4.07-4.11 (m, 1 H), 7.28 (d, J = 7.6 Hz, 1 H), 7.31 (d, J = 7.6 Hz, 1 H), 7.44(t, J = 7.6 Hz, 1 H), 7.46 (t, J = 7.6 Hz, 1 H), 7.59 (d, J = 7.6 Hz, 1 H), 7.63 (d, J = 7.6 Hz, 1 H). ¹H NMR (400 MHz, CDCl₃): δ (mixture of isomers) = 0.99 (t, J = 7.3 Hz, 1.08 H, minor isomer), 1.03 (t, J = 7.3 Hz, 1.92 H, major isomer), 1.38 (s, 0.64 H, major isomer), 1.51-1.66 (m, 2 H), 1.71 (s, 0.36 H, minor isomer), 3.19 (dd, J = 17.6 Hz, J = 3.0 Hz, 0.36 H, minor isomer), 3.32 (dd, J = 17.6 Hz, J = 7.1 Hz, 0.64 H, major isomer), 3.39 (dd, J = 17.6 Hz, J = 4.4 Hz, 0.64 H, major isomer), 3.46(dd, J = 17.6 Hz, J = 8.3 Hz, 0.36 H, minor isomer), 3.60-3.67 (m, 0.36 H, minor isomer), 3.73-3.79 (m, 1 H), 4.03-4.07 (m, 0.64 H, major isomer), 7.20-7.62 (m, 6 H). ¹³C NMR (100 MHz, CDCl₃): δ = (major isomer) = 10.58, 27.39, 31.30, 49.00, 75.37, 119.04, 119.35, 122.21, 123.30, 127.66, 128.00, 131.44, 139.54, 144.76, 145.95. EI-MS: m/z = 212 [M⁺]. Anal. Calcd for C₁₅H₁₆O: C, 84.87; H, 7.60. Found: C, 84.72; H, 7.55.
1-(1-Hydroxybutyl)acenaphthene (8b)
Diastereomer ratio, 62:38; mp 67-69 °C (major isomer), 96-99 °C (minor isomer). IR (neat): 3560, 3460, 3040, 2960, 2930, 2870, 1620, 1600, 1500 cm^-1. ¹H NMR (400 MHz, CDCl₃): δ (major isomer) = 0.97 (t, J = 7.0 Hz, 3 H), 1.32 (s, 1 H), 1.37-1.62 (m, 4 H), 3.33 (dd, J = 17.4 Hz, J = 7.7 Hz, 1 H), 3.40 (dd, J = 17.4 Hz, J = 4.6Hz, 1 H), 3.77 (ddd, J = 7.7 Hz, J = 4.6 Hz, J = 2.4 Hz, 1 H), 4.16-4.17 (m, 1 H), 7.27 (d, J = 7.6 Hz, 1 H), 7.29 (d, J = 7.6 Hz, 1 H), 7.44 (t, J = 7.6 Hz, 1 H), 7.45 (t, J = 7.6 Hz, 1 H), 7.58 (d, J = 7.6 Hz, 1 H), 7.62 (d, J = 7.6 Hz, 1 H). ¹H NMR (400 MHz, CDCl₃): δ (minor isomer) = 0.94(t, J = 7.1 Hz, 3 H), 1.37-1.61 (m, 4 H), 1.70 (s, 1 H), 3.22 (d, J = 17.4 Hz, 1 H), 3.49 (dd, J = 17.4 Hz, J = 7.6 Hz, 1 H), 3.76-3.78 (m, 2 H), 7.27 (d, J = 7.6 Hz, 1 H), 7.39-7.46 (m, 3 H), 7.59 (d, J = 7.6 Hz, 1 H), 7.63 (d, J = 7.6 Hz, 1 H). ¹³C NMR (100 MHz, CDCl₃): δ = (major isomer) = 14.11, 19.36, 31.34, 36.60, 49.39, 73.56, 119.06, 119.35, 122.21, 123.29, 127.66, 127.99, 131.42, 139.54, 144.77, 145.95. ¹³C NMR (100 MHz, CDCl₃): δ (minor isomer) = 14.04, 19.23, 34.30, 36.69, 49.68, 74.90, 119.25, 120.53, 122.35, 123.32, 127.64, 127.86, 131.55, 139.31, 144.39, 145.51. EI-MS: m/z = 226 [M⁺]. Anal. Calcd. for C₁₆H₁₈O: C, 84.91; H, 8.02. Found: C, 85.15; H, 7.96.
1-(1-Hydroxy-2-methylpropyl)acenaphthene (8c)
Diastereomer ratio, 75:25. IR (neat): 3450, 3040, 2960, 2870, 1620, 1600, 1590, 1500 cm^-1. ¹H NMR (400 MHz, CDCl₃): δ (mixture of isomers) = 1.07 (d, J = 6.8 Hz, 0.75 H, minor isomer), 1.08 (d, J = 6.8 Hz, 2.25 H, major isomer), 1.11 (d, J = 6.8 Hz, 0.75 H, minor isomer), 1.14 (d, J = 6.8 Hz, 2.25 H, major isomer), 1.22(d, J = 3.2 Hz, 0.75 H, major isomer), 1.45(d, J = 6.4 Hz, 0.25 Hz, minor isomer), 1.93-2.11 (m, 1 H), 3.22 (dd, J = 16.8 Hz, J = 3.6 Hz, 0.25 H, minor isomer), 3.36 (dd, J = 17.4 Hz, J = 8.2 Hz, 0.75 H, major isomer), 3.43-3.97 (m, 3 H), 7.28-7.65 (m, 6 H).
EI-MS: m/z = 226 [M⁺]. Anal. Calcd for C₁₆H₁₈O: C, 84.91; H, 8.02. Found: C, 84.85; H, 8.19.
1-(1-Hydroxybutyl)-1-methylacenaphthene (8d)
Diastereomer ratio, 65:35. IR (neat): 3450, 3040, 2960, 2870, 1620, 1600, 1500 cm^-1. ¹H NMR (400 MHz, CDCl₃): δ (major isomers) = 0.90 (t, J = 7.3 Hz, 3 H), 1.20-1.60 (m, 8 H), 2.96 (d, J = 17.1 Hz, 1 H), 3.54 (d, J = 17.1 Hz, 1 H), 3.66-3.69 (m, 1 H), 7.20-7.62 (m, 6 H). ¹H NMR (400 MHz, CDCl₃): δ (minor isomer) = 0.84 (t, J = 7.2 Hz, 3 H), 1.17-1.63 (m, 7 H), 1.72 (s, 1 H), 3.04 (d, J = 17.2 Hz, 1 H), 3.52 (d, J = 17.2 Hz, 1 H), 3.81-3.84 (m, 1 H), 7.22-7.64 (m, 6 H). ¹³C NMR (100 MHz, CDCl₃): δ (major isomer) = 14.02, 19.78, 25.63, 33.68, 40.88, 52.86, 77.75, 118.09, 119.39, 122.30, 123.34, 127.73, 127.99, 131.33, 138.30, 143.57, 150.55. ¹³C NMR (100 MHz, CDCl₃): δ (minor isomer) = 13.93, 19.92, 24.41, 34.23, 41.87, 52.60, 78.13, 118.75, 119.30, 122.37, 123.27, 127.73, 127.97, 131.46, 138.04, 143.48, 150.90. EI-MS: m/z = 240 [M⁺]. Anal. Calcd for C₁₇H₂₀O: C, 84.96; H, 8.39. Found: C, 84.79; H, 8.61.
1-(1-Hydroxy-1-phenylethyl) acenaphthene (8e)
Diastereomer ratio, 63:37; mp 147-150 °C (minor isomer). IR (neat): 3540, 3450, 3090, 3050, 3030, 2970, 2930, 1600, 1590, 1490 cm^-1. ¹H NMR (400 MHz, CDCl₃): δ (minor isomer)= 1.56 (s, 3 H), 1.72 (s, 1 H), 3.41 (dd, J = 17.6 Hz, J = 7.6 Hz, 1 H), 3.47 (dd, J = 17.6 Hz, J = 4.8 Hz, 1 H), 4.30 (dd, J = 7.6 Hz, J = 4.8 Hz, 1 H), 6.48 (d, J = 6.8 Hz, 1 H), 7.20-7.58 (m, 10 H). ¹H NMR (400 MHz, CDCl₃): (mixture of isomers) = 1.53 (s, 1.11 H, minor), 1.59 (s, 1.89 H, major), 1.73 (s, 0.63 H, major), 1.78 (s, 0.37, minor), 3.23-3.46 (m, 2 H), 4.20 (dd, J = 8.0 Hz, J = 3.2 Hz, 0.63 H, major), 4.26 (dd, J = 7.2 Hz, J = 4.8 Hz, 0.37 H, minor), 6.45 (d, J = 6.8 Hz, 0.37 H, minor), 7.00 (d, J = 6.8 Hz, 0.63 H, major), 7.20-7.61 (m, 10 H). ¹³C NMR (100 MHz, CDCl₃): δ (minor isomer) = 27.32, 33.84, 54.42, 76.85, 119.06, 121.37, 122.27, 123.47, 125.41, 126.90, 127.40, 127.68, 128.27, 131.29, 139.78, 143.88, 144.06, 147.71. EI-MS: m/z = 274 [M⁺]. Anal. Calcd for C₂₀H₁₈O: C, 87.56; H, 6.61. Found: C, 87.73; H, 6.82.
γ-(1,2-Diphenylethyl)-γ-methyl-γ-lactone (14)
Diastereomer ratio, 63:37; mp 134-136 °C (major isomer). IR (neat): 3020, 2970, 1750, 1600, 1500, 1460, 1380, 1140 cm^-1. ¹H NMR (270 MHz, CDCl₃): δ (major isomer) = 1.40 (s, 3 H), 1.71-1.82 (m, 1 H), 2.26-2.61 (m, 3 H), 3.04-3.11 (m, 2 H), 3.27-3.31 (m, 1 H), 6.72-7.27 (m, 10 H). ¹H NMR (270 MHz, CDCl₃): δ (mixture of isomers) = 1.40 (s, 1.89 H, major isomer), 1.48 (s, 1.11 H, minor isomer), 1.71-2.63 (m, 4 H), 3.00-3.11 (m, 2 H), 3.24-3.31 (m, 1 H), 6.72-7.27 (m, 10 H). ¹³C NMR (67.8 MHz, CDCl₃): δ (major isomer) = 24.05, 28.96, 32.46, 36.18, 57.54, 88.50, 125.74, 127.02, 127.95, 128.14, 128.72, 129.48, 138.50, 139.69, 176.40. EI-MS: m/z = 280 [M⁺]. Anal. Calcd for C₁₉H₂₀O₂: C, 81.40; H, 7.19. Found: C, 81.45; H, 7.28.

13

α-Methylstilbene (1b) was prepared by the reaction of benzylmagnesium chloride with benzaldehyde followed by dehydration.
α-Methylstilbene (1b)
Mp: 79-81 °C. IR (neat): 3080, 3050, 3030, 2990, 2960, 1960, 1990, 1620, 1600 cm^-1. ¹H NMR (270 MHz, CDCl₃): δ = 2.27 (s, 3 H), 6.83(s, 1 H), 7.23-7.53 (m, 10 H). ¹³C NMR (CDCl₃): δ = 17.56, 125.89, 126.35, 127.07, 127.67, 128.05, 128.21, 129.02, 137.29, 138.23, 143.83. EI-MS: m/z = 194 [M⁺].

14

1-Methylacenaphthylene (7b) was prepared by the reported method. See: Bosch A., Brown R. K.; Can. J. Chem.; 1968, 46: 715
1-Methylacenaphthylene (7b) IR (neat): 3060, 3040, 2970, 2910, 1620, 1550 cm^-1. ¹H NMR (400 MHz, CDCl₃): δ = 2.38 (d, J = 1.4 Hz, 3 H), 6.65(d, J = 1.4 Hz, 1 H), 7.39-7.49 (m, 3 H), 7.56 (d, J = 7.6 Hz, 1 H), 7.63 (d, J = 7.6 Hz, 1 H), 7.72 (d, J = 7.6 Hz, 1 H). ¹³C NMR (CDCl₃): δ = 13.10, 121.64, 122.28, 125.24, 125.79, 127.07, 127.31, 127.69, 127.82, 128.92, 139.76, 140.24, 140.99. EI-MS: m/z = 166 [M⁺].

15

The possibility of protonation prior to the electrophilic attack of carbonyl compounds 2 on the anion radical species 9 may be excluded in the present cross-coupling because the first protonation to 9 generated from α-methylstilbene(1a) lead to generation of more unstable tertiary carbanion, which may be difficult to form, in order to confirm the observed regioselectivity.

16

As another possible explanation for unusual regioselectivity of this reaction, it may seem operative that the tertiary carbanion of the α-position of the anion radical species 9 may be more unstable, but more reactive than the secondary carbanion of 9 to be preferentially subjected to electrophilic attack of carbonyl compounds 2.

17 Takahashi T. Swanson DR. Negishi E. Chem. Lett. 1987, 623