Nonepimerizing Alkylation of H–P Species to Stereospecifically

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Nonepimerizing Alkylation of H−P Species to Stereospecifically Generate P‑Stereogenic Phosphine Oxides: A Shortcut to Bidentate Tertiary Phosphine Ligands Shao-Zhen Nie,† Zhong-Yang Zhou,† Ji-Ping Wang, Hui Yan, Jing-Hong Wen, Jing-Jing Ye, Yun-Yao Cui, and Chang-Qiu Zhao* College of Chemistry and Chemical Engineering, Liaocheng University, Liaocheng, Shandong 252059, China S Supporting Information *

ABSTRACT: The secondary RP-(−)-menthyl alkylphosphine oxide was confirmed as configurationally stable toward base and was used in base-promoted alkylation, stereospecifically affording P-retained bis or functional tertiary phosphine oxides in excellent yields. The alkylated products were deoxygenated using oxalyl chloride followed by ZnCl2−NaBH4 to form P-inversed bidentate phosphine boranes in high stereoselectivities.

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INTRODUCTION The chiral tertiary phosphines are of high importance to asymmetric synthesis because they are used both as ligands of metallic catalysts1 and as organocatalysts.2 Compared to the phosphines having a chiral carbon skeleton, the P-stereogenic counterparts show an excellent asymmetric induction effect because the stereogenic center is closer to the active center.3 Bidentate phosphine ligands are most frequently applied in metallic catalysts to form chelated complexes that are stable and supply a more significant asymmetric reactive site. The Pstereogenic bidentate ligands are traditionally acquired via multistep reactions, as represented by (R,R)-DIPAMP,4 or tedious resolutions.4,5 Although the recently developed asymmetric reactions of racemic or pro-chiral phosphines6−9 effectively afforded mono P-stereogenic centers in excellent but imperfect stereoselectivities, more than one diastereomer was formed during their expansion to the preparation of multiple or bidentate P-stereogenic phosphines.6 The configurationally instability of phosphorus atom also restricted the applications of P-stereogenic phosphines. Because the H−P species are easily racemized or epimerized, their preparation and conversion are usually carried out very meticulously, sometimes at low temperature (Chart 1).7−11 For example, a bidentate ligand QuinoxP was obtained via an nBuLi promoted substitution with P-stereogenic secondary phosphine borane at −78 °C.12 The harsh conditions also restrict the scope of substrates with sensitive functional groups.8−14 During the usage as catalysts, the P-stereogenic centers also easily lost chirality under some conditions such as strong acid, base or at high temperature.7a,15 Thus, easily © 2017 American Chemical Society

accessible and configurationally stable P-stereogenic substances are highly desirable. We proposed introducing a chiral alkyl group to phosphorus, which not only constructed one of the three C−P bonds of the tertiary phosphine but also acted as a chiral source to assist the asymmetric induction. Importantly, the presence of chiral alkyl could stabilize the conf iguration on phosphorus. In addition, the self-resolution of chiral alkyl will be helpful in isolating Pstereogenic starting materials or products.16 Herein, we disclosed a nonepimerizing alkylation of RP-(−)-menthyl alkylphosphine oxide 1, whose configuration on phosphorus was stabilized by (−)-menthyl. As recently reported by us and other groups, some base-promoted reactions of chiral P−H species could be carried out at ambient temperature.7a,17 However, to the best of our knowledge, their configurationally stability in an anion state has never been confirmed (Chart 1).

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RESULTS AND DISCUSSION The stabilization of P-configuration by (−)-menthyl group was also observed for tertiary phosphine oxides. As recently reported by Gilheany, the chlorophosphonium salts were reduced by sodium borohydride to afford the phosphine boranes with loss of chirality on phosphorus.18 However, we found that a similar reduction of (−)-menthyl-substituted phosphine oxides afforded the P-stereogenic phosphine boranes in excellent stereoselectivity. Thus, the extreme shortcut to Pstereogenic phosphine ligands was established.19 Received: June 7, 2017 Published: August 16, 2017 9425

DOI: 10.1021/acs.joc.7b01413 J. Org. Chem. 2017, 82, 9425−9434

Article

The Journal of Organic Chemistry Chart 1. Comparison of Our Work to Commonly Recognized Reactions

nBu4NOH gave similar results (entries 3−4). The usage of stronger bases such as LDA or n-BuLi in ether or THF, either in one or in half an equivalence, also did not lead to the detection of SP-1a′ (entries 5−8). At elevated temperature, for KOH in ethanol at 80 °C (entry 2) and n-BuLi in THF at 50 °C (entry 9), SP-1a′ was still not detected. When a mixture of 1a/1a′ (40:60) was treated with n-BuLi at room temperature, the ratio basically kept unchanged (entry 9). Under similar conditions, menthoxyl substituted RP-phenylphosphinate 1b7b was totally epimerized (entries 11 and 12). In the presence of tBuOK or KOH/t-BuOH, SP-menthyl phenylphosphine-borane 1c′21 was partly epimerized (entries 13 and 14). Under alkali condition, the two stereoisomers of ordinary Pstereogenic sec-phosphine oxides were reversibly converted via the phosphinite salts.8 However, the phosphinite salts of 1a were confirmed as configurationally stable. The treatment of 1a with equimolar n-BuLi afforded a white solid. On its NMR spectrum, the signals of 1a, at 6.86 (1H) and 33.3 (31P), almost could not be observed. After acidification, the two signals were appeared, and that of 1a′ was not detected. On 31P NMR spectrum, the peak at 33.3 ppm of 1a was also appeared after acidification. The observations indicated the formation of the lithium salt of 1a that was converted back to 1a upon acidification. When reacted with methyl iodide in acetonitrile, the lithium salt afforded methylated product in a single stereomer. Similarly, the soldium salt of 1a was isolated, and showed the configurationally stability (Scheme 1, vide infra, also as seen in SI). The unusual configuration stability of 1a was attributed to the (−)-menthyl group that prevented the conversion of the two stereoisomers. However, the epimerization of 1c′ indicated that when the oxygen was replaced with borane, the configuration on phosphorus became unstable.21 As shown in Part A of Scheme 2, 1a was converted to phosphinite anion 1aA by a base, in which the lone pair electrons occupied a large volume. In the supposed transition state 1aTS, the gauche interactions of oxygen anion or phenyl to isopropyl resulted in

First, the configuration stability of 1 toward various bases was examined. When RP-1a was stirred with KOH in DMF at room temperature for 15 h, none of the signals except for the peaks of 1a, at 6.86 (1H) and 33.3 ppm (31P), were observed during NMR spectrum (entry 1 of Table 1).20 Ca(OH)2 and Table 1. Examination of Epimerization of 1 in the Presence of Base

entry

a

1

solvent DMF EtOH DMF

rt/15 h 80 °C/18 h rt/15 h

>99:1 >99:1 >99:1

DMF

rt/18 h

>99:1

Et2O Et2O

rt/28 h −80 °C to rt/ 14 h −80 °C to rt/ 14 h −80 °C to rt/ 14 h −80 to 50 °C/ 7h −80 °C to rt/ 17 h rt/28 h −80 °C to rt/ 14 h rt/41 h rt/22 h

>99:1 >99:1

1 2 3

1a 1a 1a

4

1a

5 6

1a 1a

KOH (1.2) KOH (1.2) Ca(OH)2 (1.2) n-Bu4NOH (1.2) LDA (1.2) LDA (0.6)

7

1a

n-BuLi (1.2)

THF

8

1a

n-BuLi (0.6)

THF

9

1a

n-BuLi (1.2)

THF

10

n-BuLi (0.6)

THF

11 12

1a/1a′ (40:60) 1b 1b

LDA (1.2) LDA (0.6)

Et2O Et2O

13 14

1c′ 1c′

KOH (0.3) KOH (0.3)

EtOH t-BuOH

temp/time

1:1′a

base (equiv)

>99:1 >99:1 >99:1 (38:62) 60:40 46:54 99:1. All reactions were carried out under N2 atmosphere in dry glassware using Schlenk-line techniques. Air and moisture sensitive liquids and solutions were transferred via syringe. Oxalyl chloride was distilled prior to use. Experimental Procedure for Synthesis of 3 or 5. Method A. To the mixture of 1a (52.8 mg, 0.2 mmol) and calcium hydroxide (17.8 mg, 0.24 mmol), DMF (0.5 mL) was added, followed by the addition of benzyl bromide (51.3 mg, 0.3 mmol). The mixture was stirred at room temperature for 30 h, and monitored with TLC and/or 31 P NMR. After the reaction was completed, saturated aqueous ammonium chloride (3 mL) was added. The mixture was extracted with dichloromethane (3 × 10 mL), washed with water, dried over anhydrous magnesium sulfate. After removing the solvent in vacuo, the residue was purified with column chromatography on silica gel (petroleum ether/ethyl acetate = 2/1) to afford desired product 3a. Method B. To the mixture of 1a (52.8 mg, 0.2 mmol) and potassium hydroxide (13.5 mg, 0.24 mmol), CH3CN (0.5 mL) was added, followed by the addition of benzyl bromide (51.3 mg, 0.3 mmol). The mixture was stirred at room temperature for 30 h, and monitored with TLC and 31P NMR. After the reaction was completed, saturated aqueous ammonium chloride (3 mL) was added. The mixture was extracted with dichloromethane (3 × 10 mL), washed with water, dried over anhydrous magnesium sulfate. After removing the solvent in vacuo, the residue was purified with column chromatography on silica gel (petroleum ether/ethyl acetate = 2/1) to afford desired product 3a. Method C. The solution of 1a (52.8 mg, 0.2 mmol) in THF (0.5 mL) was cooled to −80 °C, then the solution of nBuLi (1.6 M solution in hexane, 0.36 mL, 0.227 mmol) was added dropwise. The resulted solution was stirred at −80 °C for 0.5 h, 3-bromopropanenitrile (27 mg, 0.2 mmol) was added dropwise. The mixture was warmed to room temperature while the stirring was continued for 10 h, and monitored with TLC and/or 31P NMR (ca. 0.1 mL suspension was dissolved in 0.4 mL chloroform). After the reaction was completed, saturated aqueous ammonium chloride (3 mL) was added. The mixture was extracted with dichloromethane (3 × 10 mL), washed with water, dried over anhydrous magnesium sulfate. After removing the solvent in vacuo, the residue was purified by column chromatography on silica gel (petroleum ether/ethyl acetate = 1/1) to afford desired product 3o. (RP)-(−)-Menthyl benzylphenylphosphine oxide, 3a. The specimen was obtained from Method A or B for 30 h. The ratio of crude 3a/3a′ was detected as >99:1 dr (estimated by 1H NMR spectra), and the pure compound was obtained as a white solid (65 mg, 92%, >99:1 dr) from flash chromatography (silica gel, petroleum ether/ethyl acetate = 1/1 as eluent). [α]20 D = −132.58, (c = 0.20, CH2Cl2). mp 208.5−210.5 °C. 31P NMR (162 MHz, CDCl3) δ = 41.11 (s). 1H NMR (400 MHz, CDCl3) δ = 7.56−7.47 (m, 2H), 7.41−7.29 (m, 3H), 7.11−7.04 (m, 3H), 6.99 (s, 2H), 3.51 (dd, J = 16.8 Hz, 14.4, 1H), 3.04 (dd, J = 14.0, 7.6 Hz, 1H), 2.16−1.96 (m, 3H), 1.79−1.66 (m, 6H), 1.49−1.35 (m, 2H), 1.07−1.01 (m, 1H), 0.97 (d, J = 5.6 Hz, 4H), 0.77 (d, J = 6.8 Hz, 3H), 0.31 (d, J = 7.2 Hz, 3H). 13C NMR (101 MHz, CDCl3) δ = 134.7 (s), 133.8 (s), 132.1 (d, J = 7.6 Hz), 131.0 (d, J = 2.7 Hz), 130.7 (s), 130.7 (s), 130.3 (s), 130.3 (s), 128.2 (s), 128.2 (s), 128.2 (s), 128.1 (s), 126.5 (d, J = 2.7 Hz), 43.6 (d, J = 3.6 Hz), 40.8 (d, J = 65.7 Hz), 36.5 (d, J = 60.1 Hz), 35.6 (d, J = 2.5 Hz), 34.5 (s), 33.6 (d, J = 12.9 Hz), 28.3 (d, J = 2.9 Hz), 24.9 (d, J = 11.9 Hz), 22.9 (s), 21.7 (s), 15.4 (s). IR (KBr) ν/cm−1 2928, 1454, 1188, 754, 534,. HRMS (ESI+) Calcd for C23H32OP [M + H+] 355.2180, found 355.2185. (RP)-(−)-Menthyl (2-bromobenzyl)phenylphosphine oxide, 3b. The specimen was obtained from Method A for 60 h. The ratio of crude 3b/3b′ was detected as >99:1 dr (estimated by 1H NMR spectra), and the pure compound was obtained as a white solid (71 mg, 82%, >99:1 dr) from flash chromatography (silica gel, petroleum ether/ethyl acetate = 2/1 as eluent). [α]34 D = −72.3, (c = 0.47, CH2Cl2). mp 178.1−178.7 °C. 31P NMR (162 MHz, CDCl3) δ = 41.90 (s). 1H NMR (400 MHz, CDCl3) δ = 7.67−7.50 (m, 3H), 7.43−7.30 (m, 4H), 7.12 (t, J = 7.6 Hz, 1H), 6.94 (t, J = 8.0 Hz, 1H), 3.65 (t, J = 15.2 Hz, 1H), 3.47 (dd, J = 14.8, 8.4 Hz, 1H), 2.20−2.08

(m, 1H), 2.07−1.92 (m, 3H), 1.79−1.66 (m, 3H), 1.50−1.35 (m 2H), 1.07−0.98 (m, 1H), 0.96 (d, J = 5.6 Hz, 3H), 0.75 (d, J = 6.8 Hz, 3H), 0.35 (d, J = 6.8 Hz, 3H). 13C NMR (101 MHz, CDCl3) δ = 134.3 (s), 133.4 (s), 132.6 (d, J = 5.9 Hz), 132.1 (d, J = 4.0 Hz), 131.2 (s), 130.9 (s), 130.8 (s), 128.2 (s), 128.1 (s), 127.3 (d, J = 2.0 Hz), 125.3 (d, J = 7.3 Hz), 43.5 (d, J = 3.6 Hz), 41.2 (d, J = 66.2 Hz), 35.4 (s), 35.3 (s), 34.7 (s), 34.4 (s), 33.5 (d, J = 13.0 Hz), 28.4 (d, J = 2.7 Hz), 24.9 (d, J = 12.1 Hz), 22.8 (s), 21.6 (s), 15.4 (s). HRMS (ESI+) Calcd for C23H31BrOP [M + H+] 433.1296, found 433.1301. (RP)-(−)-Menthyl (2-methylbenzyl)phenylphosphine oxide, 3c. The specimen was obtained from Method B for 11 h. The ratio of crude 3c/3c′ was detected as >99:1 dr (estimated by 1H NMR spectra), and the pure compound was obtained as a white solid (64 mg, 87%, >99:1 dr) from flash chromatography (silica gel, petroleum ether/ethyl acetate = 2/1 as eluent). [α]34 D = −115.7, (c = 0.23, CH2Cl2). mp 187.0−190.9 °C. 31P NMR (162 MHz, CDCl3) δ = 40.44 (s). 1H NMR (400 MHz, CDCl3) δ7.52 (t, J = 8.4 Hz, 2H), 7.39 (t, J = 7.2 Hz, 1H), 7.35−7.28 (m, 2H), 7.05−6.92 (m, 2H), 6.84 (t, J = 7.2 Hz, 1H), 6.76 (d, J = 7.6 Hz, 1H), 3.58 (dd, J = 16.8, 14.8 Hz, 1H), 2.99 (dd, J = 14.0, 7.6 Hz, 1H), 2.20 (s, 3H), 2.13−2.05 (m, 2H), 1.97−1.90 (m, 1H), 1.81−1.70 (m, 3H), 1.50−1.40 (m, 2H), 1.04 (s, 1H), 1.00 (d, J = 5.6 Hz, 4H), 0.77 (d, J = 6.8 Hz, 3H), 0.29 (d, J = 6.4 Hz, 3H). 13C NMR (101 MHz, CDCl3) δ 137.4 (d, J = 5.1 Hz), 134.7 (s), 133.8 (s), 130.8 (d, J = 2.7 Hz), 130.5 (dd, J = 9.2, 4.7 Hz), 130.1 (d, J = 2.5 Hz), 127.9 (d, J = 11.0 Hz), 126.4 (d, J = 2.9 Hz), 125.2 (d, J = 2.6 Hz), 43.3 (d, J = 3.6 Hz), 40.7 (s), 40.0 (s), 35.2 (d, J = 2.8 Hz), 34.2 (s), 33.8−33.2 (m), 33.0 (s), 28.0 (d, J = 3.0 Hz), 24.7 (d, J = 11.8 Hz), 22.7 (s), 21.4 (s), 20.1 (s), 15.2 (s). IR (KBr) ν/cm−1 2930, 1457, 1187, 749, 563. HRMS (ESI+) Calcd for C24H33OP [M + H+] 369.2347, found 369.2319. (RP)-(−)-Menthyl (4-chlorobenzyl)phenyl phosphine oxide, 3d. The specimen was obtained from Method A for 42 h. The ratio of crude 3d/3d′ was detected as >99:1 dr (estimated by 1H NMR spectra), and the pure compound was obtained as a white solid (73 mg, 94%, >99:1 dr) from flash chromatography (silica gel, petroleum ether/ethyl acetate = 2/1 as eluent). [α]34 D = −148.0, (c = 0.10, CH2Cl2). mp 185.6−188.0 °C. 31P NMR (162 MHz, CDCl3) δ = 39.78(s). 1H NMR (400 MHz, CDCl3) δ = 7.53−7.48 (m, 2H), 7.43− 7.30 (m, 3H), 7.04 (d, J = 8.2 Hz, 2H), 6.90 (d, J = 7.2 Hz 2H), 3.48 (dd, J = 17.2, 14.4 Hz, 1H), 2.97 (dd, J = 14.4, 7.2 Hz, 1H), 2.20−2.06 (m, 1H), 2.05−1.94 (m, 2H), 1.79−1.67 (m, 3H), 1.47−1.37 (m, 2H), 1.06−1.01 (m, 1H), 0.96 (d, J = 5.6 Hz, 3H), 0.78 (d, J = 6.8 Hz, 4H), 0.29 (d, J = 6.8 Hz, 3H). 13C NMR (101 MHz, CDCl3) δ = 134.1 (s), 133.2 (s), 132.2 (d, J = 3.2 Hz), 131.2 (d, J = 4.9 Hz), 130.9 (d, J = 2.7 Hz), 130.4 (d, J = 8.1 Hz), 130.3 (d, J = 9.1 Hz), 128.1 (s), 128.0 (s), 128.0 (s), 43.3 (d, J = 3.7 Hz), 40.9 (s), 40.2 (s), 36.0 (s), 35.4 (s), 35.2 (d, J = 2.0 Hz), 34.1 (s), 33.2 (d, J = 12.9 Hz), 28.1 (d, J = 2.9 Hz), 24.5 (d, J = 12.0 Hz), 22.6 (s), 21.4 (s), 15.1(s). HRMS (ESI+) Calcd for C23H31ClOP [M + H+] 389.1801, found 389.1808. (RP)-(−)-Menthyl (4-methylbenzyl) phenyl phosphine oxide, 3e. The specimen was obtained from Method B for 12 h. The ratio of crude 3e/3e′ was detected as >99:1 dr (estimated by 1H NMR spectra), and the pure compound was obtained as a white solid (68 mg, 92%, >99:1 dr) from flash chromatography (silica gel, petroleum ether/ethyl acetate = 2/1 as eluent). [α]34 D = −109.4, (c = 0.13, CH2Cl2). mp 206.8−208.8 °C. 31P NMR (162 MHz, CDCl3) δ = 39.83 (s). 1H NMR (400 MHz, CDCl3) δ 7.63−7.47 (m, 2H), 7.40− 7.28 (m, 3H), 6.95−6.79 (m, 4H), 3.46 (dd,J = 16.4, 14.8 Hz, 1H), 3.03 (dd, J = 14.4, 8.0 Hz, 1H), 2.21 (s, 3H), 2.12−1.92 (m, 3H), 1.80−1.46 (m, 3H), 1.46−1.32 (m, 2H), 1.06−0.88 (m, 5H), 0.77 (d, J = 6.8 Hz, 3H), 0.31 (d, J = 6.4 Hz, 3H). 13C NMR (101 MHz, CDCl3) δ 135.7 (s), 134.5 (s), 133.6 (s), 130.8−130.1 (m), 129.9 (d, J = 5.0 Hz,), 128.6 (t, J = 8.2 Hz), 127.9 (d, J = 11.1 Hz), 43.4 (d, J = 3.5 Hz), 41.0 (s), 40.3 (s), 36.0 (s), 35.4 (d, J = 2.5 Hz), 34.2 (s), 33.3 (d, J = 12.9 Hz), 28.1 (s), 24.6 (d, J = 11.9 Hz), 22.6 (s), 21.4 (s), 20.9 (s), 15.1 (s). IR (KBr) ν/cm−1 2949, 1438, 1182, 838, 570. HRMS (ESI+) Calcd for C24H34OP [M + H+] 369.2347, found 369.2316. (RP)-(−)-Menthyl (4-tert-butylbenzyl) phenyl phosphine oxide, 3f. The specimen was obtained from Method B for 13 h. The ratio of crude 3f/3f′ was detected as >99:1 dr (estimated by 1H NMR 9429

DOI: 10.1021/acs.joc.7b01413 J. Org. Chem. 2017, 82, 9425−9434

Article

The Journal of Organic Chemistry

2H), 1.80−1.71 (m, 4H), 1.49−1.39 (m, 2H), 0.97 (d, J = 5.6 Hz, 4H), 0.77 (d, J = 6.8 Hz, 3H), 0.30 (d, J = 6.8 Hz, 3H). 13C NMR (101 MHz, CDCl3) δ = 137.0 (s), 134.0 (s), 133.1 (s), 132.4 (d, J = 7.6 Hz), 130.9 (d, J = 2.7 Hz), 130.4 (s), 130.4 (s), 130.3 (s), 130.3 (s), 130.1 (s), 130.0 (s), 128.3 (d, J = 3.0 Hz), 128.1 (s), 128.0 (s), 46.01 (s), 43.3 (d, J = 3.7 Hz), 40.7 (s), 40.0 (s), 36.6 (s), 36.0 (s), 35.2 (s), 34.2 (s), 33.3 (d, J = 13.0 Hz), 28.1 (d, J = 3.0 Hz), 24.6 (d, J = 11.9 Hz), 22.6 (s), 21.4 (s), 15.1 (s). HRMS (ESI+) Calcd for C24H33ClOP [M + H+] 403.1958, found 403.1970. (RP)-(−)-Menthyl methyl phenyl phosphine oxide, 3j. The specimen was obtained from Method A, B for 12 h. The ratio of crude 3j/3j′ was detected as >99:1 dr (estimated by 1H NMR spectra), and the pure compound was obtained as a white solid (53 mg, 95%, >99:1 dr) from flash chromatography (silica gel, petroleum ether/ethyl acetate = 1/6 as eluent). [α]34 D = −42.6, (c = 0.34, CH2Cl2). mp 150.2−152.7 °C. 31P NMR (162 MHz, CDCl3) δ = 41.30 (s). 1H NMR (400 MHz, CDCl3) δ = 7.70 (dd, J = 13.4, 5.0 Hz, 2H), 7.53−7.41 (m, 3H), 2.24−2.11 (m, 1H), 1.92 (td, J = 11.8, 3.1 Hz, 1H), 1.73 (d, J = 10.5 Hz, 3H), 1.64 (t, J = 11.8 Hz, 4H), 1.34 (s, 1H), 2.22−1.10 (m, 1H), 1.08−0.98 (m, 1H), 0.92 (d, J = 15.2 Hz, 4H), 0.85 (d, J = 6.8 Hz, 3H), 0.42 (d, J = 6.8 Hz, 3H). 13C NMR (101 MHz, CDCl3) δ = 136.2 (s), 135.3 (s), 130.9 (d, J = 2.0 Hz), 129.9 (d, J = 9.1 Hz), 128.3 (d, J = 11.1 Hz), 43.3 (d, J = 3.2 Hz), 41.3 (s), 40.7 (s), 35.5 (d, J = 1.8 Hz), 34.2 (d, J = 1.4 Hz), 33.1 (d, J = 13.5 Hz), 28.2 (d, J = 2.9 Hz), 24.5 (d, J = 12.3 Hz), 22.5 (s), 21.5 (s), 15.2(s), 15.1(s), 14.5 (s). HRMS (ESI+) Calcd for C17H28OP [M + H+] 279.1878, found 279.1877. (RP)-(−)-Menthyl ethyl phenyl phosphine oxide, 3k. The specimen was obtained from Method A for 48 h. The ratio of crude 3k/3k′ was detected as >99:1 dr (estimated by 1H NMR spectra), and the pure compound was obtained as a white solid (54 mg, 92%, >99:1 dr) from flash chromatography (silica gel, petroleum ether/ethyl acetate = 1/3 31 as eluent). [α]34 D = −38.0, (c = 0.11, CH2Cl2). mp 163.0−167.1 °C. P NMR (162 MHz, CDCl3) δ = 44.86 (s). 1H NMR (400 MHz, CDCl3) δ = 7.72−7.64 (m, 2H), 7.51−7.41 (m, 3H), 2.16−2.00 (m, 2H), 1.98−1.90 (m, 1H), 1.89−1.81 (m, 1H), 1.80−1.58 (m, 4H), 1.34 (s, 1H), 1.30−1.18 (m, 1H), 1.05−0.94 (m, 4H), 0.92 (t, J = 6.4 Hz, 4H), 0.83 (d, J = 6.8 Hz, 3H), 0.35 (d, J = 6.8 Hz, 3H). 13C NMR (101 MHz, CDCl3) δ = 134.4 (s), 133.6 (s), 130.8 (d, J = 2.7 Hz), 130.5 (d, J = 8.4 Hz), 128.3 (d, J = 10.8 Hz), 43.2 (d, J = 3.4 Hz), 40.9 (s), 40.3 (s), 35.3 (d, J = 2.3 Hz), 34.2 (s), 33.2 (d, J = 13.0 Hz), 28.2 (d, J = 2.8 Hz), 24.6 (d, J = 11.9 Hz), 22.6 (s), 21.5 (s), 21.1 (s), 20.4 (s), 15.1 (s), 5.4 (d, J = 4.9 Hz). HRMS (ESI+) Calcd for: C18H30OP [M + H+] 293.2034, found 293.2031. (RP)-(−)-Menthyl n-butyl phenyl phosphine oxide, 3l. The specimen was obtained from Method B for 20 h. The ratio of crude 3l/3l′ was detected as >99:1 dr (estimated by 1H NMR spectra), and the pure compound was obtained as a white solid (54 mg, 84%, >99:1 dr) from flash chromatography (silica gel, petroleum ether/ethyl acetate = 1/2 as eluent). mp 99.4−102.1 °C. 31P NMR (162 MHz, CDCl3) δ = 43.39 (s). 1H NMR (400 MHz, CDCl3) δ = 7.72−7.65 (m, 2H), 7.50−7.43 (m, 3H), 2.14−2.07 (m, 1H), 2.06−2.01 (m, 1H), 1.80 (s, 3H), 1.78−1.69 (m, 4H), 1.60−1.52 (m, 1H), 1.42−1.29 (m, 3H), 1.29−1.17 (m, 1H), 1.03−0.94 (m, 1H), 0.92 (d, J = 7.2 Hz, 4H), 0.84 (t, J = 7.2 Hz, 6H), 0.35 (d, J = 6.8 Hz, 3H). 13C NMR (101 MHz, CDCl3) δ = 134.8 (d, J = 86.6 Hz), 131.1 (s), 130.8 (d, J = 9.1 Hz), 128.5 (d, J = 11.1 Hz), 43.5 (d, J = 3.3 Hz), 41.2 (d, J = 66.3 Hz), 35.6 (s), 34.5 (s), 33.5 (d, J = 12.9 Hz), 28.4 (s), 27.8 (d, J = 65.9 Hz), 24.9 (d, J = 12.0 Hz), 24.4 (d, J = 14.1 Hz), 23.6 (d, J = 3.9 Hz), 22.9 (s), 21.8 (s), 15.4 (s), 13.8 (s). HRMS (ESI+) Calcd for C20H34OP [M + H+] 321.2347, found 321.2351. (RP)-(−)-Menthyl phenethyl phenyl phosphine oxide, 3m. The specimen was obtained from Method B for 48 h. The ratio of crude 3m/3m′ was detected as >99:1 dr (estimated by 1H NMR spectra), and the pure compound was obtained as a white solid (66 mg, 90%, >99:1 dr) from flash chromatography (silica gel, petroleum ether/ethyl acetate = 1/7 as eluent). [α]34 D = −16.7, (c = 0.30, CH2Cl2). mp 145.0−147.1 °C. 31P NMR (162 MHz, CDCl3) δ = 42.57 (s). 1H NMR (400 MHz, CDCl3) δ = 7.79−7.71 (m, 2H), 7.58−7.46 (m, 3H), 7.25 (t, J = 8.0 Hz, 2H), 7.18 (d, J = 7.2 Hz, 1H), 7.11 (d, J = 7.2

spectra), and the pure compound was obtained as a white solid (76 mg, 93%, >99:1 dr) from flash chromatography (silica gel, petroleum ether/ethyl acetate = 1/1 as eluent). [α]34 D = −95.6, (c = 0.54, CH2Cl2). mp 225.8−228.9 °C. 31P NMR (162 MHz, CDCl3) δ = 40.11 (s). 1H NMR (400 MHz, CDCl3) δ 7.53 (t, J = 8.8 Hz, 2H), 7.45−7.25(m, 3H), 7.12 (d, J = 7.6 Hz, 2H), 6.92 (d, J = 7.2 Hz, 2H), 3.45 (t, J = 15.2 Hz, 1H), 3.08 (dd, J = 14.0, 8.8 Hz, 1H), 2.15−2.05 (m, 2H), 1.97 (s, 1H), 1.85−1.65 (m, 3H), 1.38 (s, 2H), 1.22 (s, 9H), 1.08−0.99 (m, 1H), 0.95 (d, J = 3.6 Hz, 4H), 0.74 (d, J = 6.4 Hz, 3H), 0.34 (d, J = 6.4 Hz, 3H). 13C NMR (101 MHz, CDCl3) δ = 149.1 (d, J = 3.0 Hz), 134.5 (s), 133.7 (s), 130.7 (d, J = 3.0 Hz), 130.5 (d, J = 8.1 Hz), 129.7 (d, J = 5.2 Hz), 128.6 (d, J = 7.6 Hz), 127.9 (d, J = 11.1 Hz), 124.9 (d, J = 2.3 Hz), 43.4 (d, J = 3.6 Hz), 41.0 (s), 40.4 (s), 35.8 (s), 35.4 (d, J = 2.4 Hz), 35.2 (s), 34.26 (s), 33.3 (d, J = 13.0 Hz), 31.24 (s), 28.1 (d, J = 2.8 Hz), 24.7 (d, J = 11.9 Hz), 22.6 (s), 21.4 (s), 15.2 (s). IR (KBr) ν/cm−1 2957, 1439, 1183, 840, 776. HRMS (ESI+) Calcd for C27H40OP [M + H+] 411.2817, found 411.2818. (RP)-(−)-Menthyl (2-naphthyl-methyl)phenylphosphine oxide, 3g. The specimen was obtained from Method B for 26 h. The ratio of crude 3g/3g′ was detected as >99:1 dr (estimated by 1H NMR spectra), and the pure compound was obtained as a white solid (69 mg, 58%, >99:1 dr) from flash chromatography (silica gel, petroleum ether/ethyl acetate = 2/1 as eluent). [α]34 D = −97.5, (c = 0.20, CH2Cl2). mp 183.4−186.6 °C. 31P NMR (162 MHz, CDCl3) δ = 40.15 (s). 1H NMR (400 MHz, CDCl3) δ = 7.73−7.65 (m, 1H), 7.60 (d, J = 4.4 Hz, 1H), 7.57−7.50 (m, 3H), 7.44 (s, 1H), 7.40−7.33 (m, 3H), 7.31−7.23 (m, 2H), 7.11 (d, J = 8.0 Hz, 1H), 3.67 (t, J = 15.6 Hz, 1H), 3.20 (dd, J = 14.0, 8.0 Hz, 1H), 2.25−2.11 (m, 1H), 2.09−2.00 (m, 2H), 1.83−1.71 (m, 3H), 1.53−1.37 (m, 2H), 1.10−1.02 (m, 1H), 0.98 (d, J = 5.2 Hz, 4H), 0.76 (d, J = 6.4 Hz, 3H), 0.31 (d, J = 6.8 Hz, 3H). 13C NMR (101 MHz, CDCl3) δ = 134.1 (s), 133.1 (d, J = 3.0 Hz), 131.9 (d, J = 2.0 Hz), 130.9 (d, J = 2.7 Hz), 130.4 (d, J = 8.5 Hz), 129.3 (d, J = 8.0 Hz), 128.8 (d, J = 6.3 Hz), 128.2 (d, J = 4.0 Hz), 128.0 (d, J = 11.1 Hz), 27.4 (d, J = 6.6 Hz), 125.7 (s), 125.3 (s), 50.6 (s), 43.4 (d, J = 3.7 Hz), 40.9 (s), 40.3 (s), 36.7 (s), 36.1 (s), 35.4 (s), 34.2 (s), 33.3 (d, J = 12.9 Hz), 28.1 (d, J = 2.9 Hz), 24.6 (d, J = 12.0 Hz), 22.6 (s), 21.4 (s), 15.1 (s). HRMS (ESI+) Calcd for C27H34OP [M + H+] 405.2269, found 405.2294. (R P )-(−)-Menthyl (2-(chloromethyl)benzyl)phenylphosphine oxide, 3h. The specimen was obtained from Method A for 47 h. The ratio of crude 3h/3h′ was detected as >99:1 dr (estimated by 1H NMR spectra), and the pure compound was obtained as a white solid (20 mg, 25%, >99:1 dr) from flash chromatography (silica gel, petroleum ether/ethyl acetate = 1/5 as eluent). [α]34 D = −150.0 (c = 0.12, CH2Cl2). mp 156.8−159.6 °C. 31P NMR (162 MHz, CDCl3) δ = 40.98 (s). 1H NMR (400 MHz, CDCl3) δ = 7.55−7.48 (m, 2H), 7.45−7.39 (m, 1H), 7.38−7.32 (m, 2H), 7.22 (t, J = 6.0 Hz, 1H), 7.06 (t, J = 7.2 Hz, 1H), 6.89 (t, J = 7.6 Hz, 1H), 6.53 (d, J = 7.6 Hz, 1H), 5.19 (d, J = 11.6 Hz, 1H), 4.45 (d, J = 11.6 Hz, 1H), 3.94 (dd, J = 16.8, 14.8 Hz, 1H), 2.98 (dd, J = 14.4, 7.2 Hz, 1H), 2.18 (td, J = 12.0, 4.2 Hz, 1H), 2.13−2.06 (m, 1H), 1.93 (dd, J = 13.2, 6.4 Hz, 1H), 1.85− 1.73 (m, 4H), 1.56−1.42 (m, 2H), 1.01 (d, J = 6.0 Hz, 4H), 0.79 (d, J = 6.8 Hz, 3H), 0.29 (d, J = 6.8 Hz, 3H). 13C NMR (101 MHz, CDCl3) δ = 137.1 (d, J = 4.5 Hz), 131.5 (d, J = 5.1 Hz), 131.2 (d, J = 9.1 Hz), 131.0 (d, J = 3.0 Hz), 130.5 (s), 130.4 (s), 130.4 (s), 128.1 (s), 128.1 (s), 128.1 (s), 128.0 (s), 126.9 (d, J = 2.8 Hz), 45.6 (s), 43.4 (d, J = 3.7 Hz), 40.6 (s), 39.9 (s), 35.1 (d, J = 2.6 Hz), 34.1 (s), 33.7 (s), 33.4 (s), 33.3 (s), 33.1 (s), 28.2 (d, J = 3.2 Hz), 24.6 (d, J = 11.9 Hz), 22.7 (s), 21.4 (s), 15.1 (s). HRMS (ESI+) Calcd for C24H33ClOP [M + H+] 403.1958, found 403.1982. (R P )-(−)-Menthyl (3-(chloromethyl)benzyl)phenylphosphine oxide, 3i. The specimen was obtained from Method A for 46 h. The ratio of crude 3i/3i′ was detected as >99:1 dr (estimated by 1H NMR spectra), and the pure compound was obtained as a white solid (15 mg, 19%, >99:1 dr) from flash chromatography (silica gel, petroleum ether/ethyl acetate = 1/6 as eluent). mp 162.3−167.2 °C. 31 P NMR (162 MHz, CDCl3) δ = 40.23 (s). 1H NMR (400 MHz, CDCl3) δ = 7.55−7.46 (m, 2H), 7.43 − (m, 3H), 7.17−7.00 (m, 2H), 7.00−6.85 (m, 2H), 4.39 (q, J = 11.2 Hz, 2H), 3.51 (dd, J = 16.8, 14.2 Hz, 1H), 3.01 (dd, J = 14.4, 7.6 Hz, 1H), 2.12 (s, 1H), 2.05−1.94 (m, 9430

DOI: 10.1021/acs.joc.7b01413 J. Org. Chem. 2017, 82, 9425−9434

Article

The Journal of Organic Chemistry

(162 MHz, CDCl3) δ = 39.48 (s). 1H NMR (400 MHz, CDCl3) δ = 7.87 (d, J = 7.2 Hz, 2H), 7.79−7.72 (m, 2H), 7.52 (t, J = 7.6 Hz, 1H), 7.42−7.35 (m, 5H), 4.00 (dd, J = 16.0, 14.4 Hz, 1H), 3.58 (t, J = 14.0 Hz, 1H), 3.25 (s, 2H) 2.31 (s, 1H), 2.03 (s, 1H), 1.86−1.70 (m, 4H), 1.50−1.44 (m, 2H), 1.13−0.99 (m, 2H), 0.96 (d, J = 6.0 Hz, 3H), 0.78 (d, J = 6.8 Hz, 3H), 0.32 (d, J = 6.4 Hz, 3H). 13C NMR (101 MHz, CDCl3) δ = 194.4 (d, J = 4.7 Hz), 137.0 (s), 133.5 (s), 131.4 (d, J = 2.7 Hz), 130.5 (d, J = 9.3 Hz), 129.0 (s), 128.4 (s), 128.2 (s), 128.1 (s), 43.1 (d, J = 3.5 Hz), 42.5 (s), 42.0 (s), 40.6 (s), 39.9 (s), 35.0 (s), 34.2 (s), 33.2 (d, J = 13.6 Hz), 28.2 (s), 24.5 (d, J = 12.8 Hz), 22.6 (s), 21.5 (s), 15.2 (s). HRMS (ESI+) Calcd for C24H32O2P [M + H+] 383.2140, found 383.2139. (RP)-2-((−)-Menthyl(phenyl)phosphoryl)acetamide, 3r. The specimen was obtained from Method A for 68 h. The ratio of crude 3r/3r′ was detected as >99:1 dr (estimated by 1H NMR spectra), and the pure compound was obtained as a white solid (63 mg, 94%, >99:1 dr) from flash chromatography (silica gel, petroleum ether/isopropanol = 1/1 as eluent). [α]34 D = −43.9, (c = 0.33, CH2Cl2). mp 193.5−194.0 °C. 31P NMR (162 MHz, CDCl3) δ = 41.74 (s). 1H NMR (400 MHz, CDCl3) δ = 7.72 (t, J = 8.0 Hz, 2H), 7.60−7.46 (m, 3H), 7.38 (s, 1H), 5.93 (s, 1H), 3.14 (t, J = 14.4 Hz, 1H), 2.86 (dd, J = 14.8, 8.8 Hz, 1H), 2.11−2.00 (m, 3H), 1.82 (s, 1H), 1.77−1.61 (m, 3H), 1.36 (s, 1H), 1.29−1.15 (m, 1H), 1.08−0.98 (m, 1H), 0.91 (d, J = 6.4 Hz, 3H), 0.83 (d, J = 6.8 Hz, 3H), 0.36 (d, J = 6.4 Hz, 3H). 13C NMR (101 MHz, CDCl3) δ = 168.1 (d, J = 4.3 Hz), 132.5 (d, J = 92.0 Hz), 131.8 (d, J = 2.7 Hz), 130.2 (d, J = 9.1 Hz), 128.6 (d, J = 11.1 Hz), 43.4 (d, J = 3.3 Hz), 41.2 (d, J = 67.9 Hz), 36.8 (d, J = 53.5 Hz), 34.9 (d, J = 2.4 Hz), 34.1 (s), 33.1 (d, J = 13.6 Hz), 28.4 (d, J = 2.9 Hz), 24.5 (d, J = 12.8 Hz), 22.5 (s), 21.4 (s), 15.0 (s). HRMS (ESI+) Calcd for C18H29NO2P [M + H+] 322.1936, found 322.1934. (RP)-(−)-Menthyl 4-methoxyphenyl 2-methylbenzyl phosphine oxide, 3s. The specimen was obtained from Method B for 47 h. The ratio of crude 3s/3s′ was detected as >99:1 dr (estimated by 1H NMR spectra), and the pure compound was obtained as a white solid (65 mg, 82%, >99:1 dr) from flash chromatography (silica gel, petroleum ether/ethyl acetate = 1/3 as eluent). mp 184.3−188.4 °C. 31P NMR (162 MHz, CDCl3) δ = 40.53 (s). 1H NMR (400 MHz, CDCl3) δ 7.50−7.37 (m, 2H), 7.05−6.92 (m, 2H), 6.91−6.72 (m, 4H), 3.81 (s, 3H), 3.62−3.43 (m, 1H), 2.98 (dd, J = 14.2, 7.8 Hz, 1H), 2.20 (s, 2H), 2.07 (s, 2H), 2.01−1.93 (m, 1H), 1.70 (s, 2H), 1.49−1.40 (m, 2H), 1.25 (s, 1H), 0.99 (d, J = 5.6 Hz, 5H), 0.78 (d, J = 7.6 Hz, 3H), 0.34 (d, J = 6.8 Hz, 3H), 0.07 (s, 1H). 13C NMR (101 MHz, CDCl3) δ 161.6 (s), 137.4 (s), 132.2 (d, J = 9.7 Hz), 130.7 (s), 130.6 (s), 130.5 (s), 130.5 (s), 130.1 (d, J = 3.0 Hz), 126.3 (d, J = 2.9 Hz), 125.3 (d, J = 2.6 Hz), 113.5 (d, J = 12.0 Hz), 55.2 (s), 43.3 (d, J = 3.7 Hz), 40.7 (s), 40.0 (s), 35.3 (s), 34.2 (s), 33.6 (s), 33.4 (s), 33.3 (s), 33.0 (s), 29.7 (s), 28.0 (d, J = 3.0 Hz), 24.7 (d, J = 11.7 Hz), 22.7 (s), 21.4 (s), 20.2 (s), 15.3 (s). HRMS (ESI+) Calcd for C25H36O2P [M + H+] 399.2453, found 399.2451. (RP)-(−)-Menthyl(benzyl)(phenyl)phosphinate, 3t. The specimen was obtained from Method A, B for 45 h. The ratio of crude 3t/3t′ was detected as >99:1 dr (estimated by 1H NMR spectra), and the pure compound was obtained as a white solid (64 mg, 86%, >99:1 dr) from flash chromatography (silica gel, petroleum ether/ethyl acetate = 1/1 as eluent). mp 160.1−162.4 °C. 31P NMR (162 MHz, CDCl3) δ = 37.12 (s). 1H NMR (400 MHz, CDCl3) δ = 7.69−7.61 (m, 2H), 7.49 (t, J = 7.6 Hz, 1H), 7.43−7.34 (m, 2H), 7.23−7.15 (m, 3H), 7.14− 7.07 (m, 2H), 4.40−4.13 (m, 1H), 3.34−3.10 (m, 2H), 2.10−1.91 (m, 1H), 1.72 (d, J = 12.0 Hz, 1H), 1.60 (t, J = 13.6 Hz, 2H), 1.39−1.21 (m, 2H), 1.02−0.91 (m, 3H), 0.86 (d, J = 6.8 Hz, 3H), 0.72 (d, J = 6.4 Hz, 6H). 13C NMR (101 MHz, CDCl3) δ = 133.1 (s), 131.9 (d, J = 2.0 Hz), 131.7 (d, J = 10.1 Hz), 131.5, 130.1 (d, J = 5.1 Hz), 128.2 (d, J = 3.0 Hz), 128.0 (s), 126.5 (d, J = 4.0 Hz), 76.6 (d, J = 8.1 Hz), 48.8 (d, J = 5.8 Hz), 43.1 (s), 39.3 (s), 38.3 (s), 34.0 (s), 31.4 (s), 25.4 (s), 22.7 (s), 21.9 (s), 21.1 (s), 15.5 (s). HRMS (ESI+) Calcd for C23H32O2P [M + H+] 371.2140, found 371.2148. (RP)-(−)-Menthyl (2-methylbenzyl)(phenyl)phosphinate, 3u. The specimen was obtained from Method A for 43 h. The ratio of crude 3u/3u′ was detected as >99:1 dr (estimated by 1H NMR spectra), and the pure compound was obtained as a white solid (69 mg, 90%, >99:1

Hz, 2H), 2.98−2.86 (m, 1H), 2.45−2.34 (m, 2H), 2.18−2.10 (m, 1H), 2.06−1.93 (m, 2H), 1.89−1.83 (m, 1H), 1.76−1.64 (m, 3H), 1.39− 1.16 (m, 2H), 1.07−0.95 (m, 1H), 0.90 (t, J = 6.0 Hz, 4H), 0.84 (d, J = 6.8 Hz, 3H), 0.36 (d, J = 6.8 Hz, 3H). 13C NMR (101 MHz, CDCl3) δ = 141.8 (d, J = 15.2 Hz), 134.6 (s), 133.8 (s), 131.1 (d, J = 2.7 Hz), 130.5 (d, J = 8.1 Hz), 128.5 (s), 128.4 (s), 128.1 (s), 126.2 (s), 43.3 (d, J = 3.4 Hz), 41.4 (s), 40.7 (s), 35.3 (d, J = 2.4 Hz), 34.2 (d, J = 1.3 Hz), 33.2 (d, J = 13.0 Hz), 30.3 (d, J = 63.3 Hz), 28.3 (d, J = 2.8 Hz), 27.5 (d, J = 3.1 Hz), 24.6 (d, J = 12.0 Hz), 22.6 (s), 21.6 (s), 15.1 (s). HRMS (ESI+) Calcd for C24H34OP [M + H+] 369.2347, found 369.2344. (RP)-(−)-Menthyl allyl phenyl phosphine oxide, 3n. The specimen was obtained from Method B for 25 h. The ratio of crude 3n/3n′ was detected as >99:1 dr (estimated by 1H NMR spectra), and the pure compound was obtained as a white solid (54 mg, 88%, >99:1 dr) from flash chromatography (silica gel, petroleum ether/ethyl acetate = 1/7 as eluent). mp 126.8−134.0 °C. 31P NMR (162 MHz, CDCl3) δ = 40.47 (s). 1H NMR (400 MHz, CDCl3) δ = 7.73−7.64 (m, 2H), 7.54−7.40 (m, 3H), 5.69−5.57 (m, 1H), 5.12−4.91 (m, 2H), 2.95− 2.82 (dd, J = 16.5, 7.7 Hz, 1H), 2.75−2.63 (m, 1H), 2.10−1.82 (m, 4H), 1.78−1.63 (m, 3H), 1.46−1.25 (m, 2H), 0.93 (d, J = 6.0 Hz, 4H), 0.81 (d, J = 6.8 Hz, 3H), 0.34 (d, J = 6.8 Hz, 3H). 13C NMR (101 MHz, CDCl3) δ = 134.1(d, J = 88.0 Hz), 131.0 (d, J = 2.7 Hz), 130.6 (d, J = 8.1 Hz), 128.2 (d, J = 11.1 Hz), 127.7 (d, J = 8.4 Hz), 120.2 (d, J = 11.0 Hz), 43.2 (d, J = 3.5 Hz), 40.6 (d, J = 65.9 Hz), 35.2 (d, J = 2.4 Hz), 35.0 (s), 34.4 (s), 34.2 (s), 33.2 (d, J = 13.1 Hz), 28.1 (d, J = 2.9 Hz), 24.6 (d, J = 12.0 Hz), 22.6 (s), 21.5 (s), 15.2 (s). HRMS (ESI+) Calcd for C19H30OP [M + H+] 305.2034, found 305.2034. (RP)-(−)-Menthyl 2-cyanoethyl phenyl phosphine oxide, 3o. The specimen was obtained from Method C for 10 h. The ratio of crude 3o/3o′ was detected as >99:1 dr (estimated by 1H NMR spectra), and the pure compound was obtained as a white solid (42 mg, 66%, >99:1 dr) from flash chromatography (silica gel, petroleum ether/ethyl acetate = 1/1 as eluent). mp 150.0−153.3 °C. 31P NMR (162 MHz, CDCl3) δ = 40.49 (s). 1H NMR (400 MHz, CDCl3) δ = 7.68 (t, J = 8.4 Hz, 2H), 7.59−7.45 (m, 3H), 2.74−2.56 (m, 1H), 2.54−2.40 (m, 1H), 2.17−1.92 (m, 5H), 1.87 (d, J = 9.6 Hz, 1H), 1.79−1.65 (m, 3H), 1.38 (s, 1H), 1.34−1.21 (m, 1H), 1.10−1.00 (m, 1H), 0.95 (d, J = 6.0 Hz, 3H), 0.84 (d, J = 6.8 Hz, 3H), 0.32 (d, J = 6.4 Hz, 3H). 13C NMR (101 MHz, CDCl3) δ = 131.8 (d, J = 3.0 Hz), 130.3 (d, J = 8.9 Hz), 128.9 (d, J = 11.1 Hz), 119.0 (d, J = 17.0 Hz), 43.2 (d, J = 3.4 Hz), 41.1 (s), 40.4 (s), 35.1 (d, J = 2.7 Hz), 34.0 (s), 33.1 (d, J = 13.2 Hz), 28.4 (d, J = 3.1 Hz), 25.0 (s), 24.5 (s), 24.4 (s), 24.3 (s), 22.5 (s), 21.4 (s), 15.0 (s), 10.3 (s). HRMS (ESI+) Calcd for C19H29NOP [M + H+] 318.1987, found 318.1989. (RP)-Ethyl3-((−)-menthyl(phenyl)phosphoryl)propanoate, 3p. The specimen was obtained from Method A for 70 h, The ratio of crude 3p/3p′ was detected as >99:1 dr (estimated by 1H NMR spectra), and the pure compound was obtained as a white solid (65 mg, 89%, >99:1 dr) from flash chromatography (silica gel, petroleum ether/ethyl acetate = 1/3 as eluent).[α]34 D = −34.0, (c = 0.20, CH2Cl2). mp 136.6−140.8 °C. 31P NMR (162 MHz, CDCl3) δ = 42.53 (s). 1H NMR (400 MHz, CDCl3) δ = 7.74−7.65 (m, 2H), 7.54−7.44 (m, 3H), 4.13−4.01 (m, 2H), 2.69−2.56 (m, 1H), 2.49−2.34 (m, 1H), 2.14−2.02 (m, 3H), 1.99−1.86 (m, 2H), 1.78−1.66 (m, 3H), 1.41− 1.25 (m, 2H), 1.19 (t, J = 7.2 Hz, 3H), 1.05−0.98 (m, 1H), 0.93 (d, J = 6.0 Hz, 4H), 0.83 (d, J = 6.8 Hz, 3H), 0.32 (d, J = 6.8 Hz, 3H). 13C NMR (101 MHz, CDCl3) δ = 172.9 (d, J = 16.2 Hz), 133.6 (d, J = 87.3 Hz), 131.2 (d, J = 2.7 Hz), 130.5 (d, J = 8.1 Hz), 128.5 (J = 11.1 Hz), 60.8 (s), 43.2 (d, J = 3.4 Hz), 40.8 (d, J = 67.8 Hz), 35.2 (d, J = 2.5 Hz), 34.1 (s), 33.2 (d, J = 13.1 Hz), 28.3 (d, J = 2.9 Hz), 26.4 (d, J = 2.0 Hz), 24.5 (d, J = 12.2 Hz), 23.4 (s), 22.8 (s), 22.6 (s), 21.5 (s), 15.1 (s), 14.1 (s). HRMS (ESI+) Calcd for C21H34O3P [M + H+] 365.2246, found 365.2243. (RP)-2-((−)-Menthyl(phenyl)phosphoryl)-1-phenylethanone, 3q. The specimen was obtained from Method A for 70 h. The ratio of crude 3q/3q′ was detected as >99:1 dr (estimated by 1H NMR spectra), and the pure compound was obtained as a white solid (60 mg, 79%, >99:1 dr) from flash chromatography (silica gel, petroleum ether/ethyl acetate = 1/5 as eluent). mp 122.5−126.8 °C. 31P NMR 9431

DOI: 10.1021/acs.joc.7b01413 J. Org. Chem. 2017, 82, 9425−9434

Article

The Journal of Organic Chemistry dr) from flash chromatography (silica gel, petroleum ether/ethyl acetate = 4/1 as eluent). [α]34 D = −38.9, (c = 0.35, CH2Cl2). mp 117.1−120.2 °C. 31P NMR (162 MHz, CDCl3) δ = 37.07 (s). 1H NMR (400 MHz, CDCl3) δ = 7.75−7.59 (m, 2H), 7.55−7.46 (m, 1H), 7.38 (td, J = 7.5, 3.4 Hz, 2H), 7.19−6.96 (m, 4H), 4.35−4.20 (m, 1H), 3.36−3.10 (m, 2H), 2.17 (s, 3H), 1.96−1.84 (m, 1H), 1.73−1.52 (m, 3H), 1.36−1.21 (m, 2H), 1.01−0.92 (m, 2H), 0.84 (d, J = 7.2 Hz, 3H), 0.78−0.65 (m, 7H). 13C NMR (101 MHz, CDCl3) δ = 137.0 (d, J = 6.1 Hz), 133.6 (s), 132.3 (s), 131.8 (d, J = 3.0 Hz), 131.6 (d, J = 10.1 Hz), 130.8 (d, J = 5.1 Hz), 130.1 (s), 130.1 (s), 130.1 (s), 128.1 (s), 128.0 (s), 126.7 (d, J = 3.0 Hz), 125.6 (d, J = 3.0 Hz), 76.4 (d, J = 8.1 Hz), 48.9 (d, J = 6.1 Hz), 43.0 (s), 36.4 (s), 35.4 (s), 34.0 (s), 31.3 (s), 25.2 (s), 22.6 (s), 21.8 (s), 21.1 (s), 19.8 (d, J = 1.0 Hz), 15.4 (s). HRMS (ESI+) Calcd for C24H34O2P [M + H+] 385.2219, found 385.2230. (RP,RP)-(1,2-Phenylenebis(methylene))bis((−)-menthyl phenyl phosphine oxide), 5a. The specimen was obtained from Method A for 72 h. The ratio of crude 5a/5a′ was detected as >99:1 dr (estimated by 1H NMR spectra), and the pure compound was obtained as a white solid (33 mg, 52%, >99:1 dr) from flash chromatography (silica gel, petroleum ether/ethyl acetate = 1/5 as 31 eluent). [α]34 D = −192.2, (c = 0.18, CH2Cl2). mp 290.8−292.7 °C. P 1 NMR (162 MHz, CDCl3) δ = 41.88 (s). H NMR (400 MHz, CDCl3) δ = 7.55−7.47 (m, 4H), 7.38−7.29 (m, 6H), 6.53 (dd, J = 5.1, 3.7 Hz, 2H), 6.26−6.17 (m, 2H), 4.73 (t, J = 15.0 Hz, 2H), 2.74 (dd, J = 14.8, 6.4 Hz, 2H), 2.26 (d, J = 9.9 Hz, 2H), 2.15−2.06 (m, 2H), 2.00−1.88 (m, 2H), 1.87−1.73 (m, 6H), 1.58−1.44 (m, 4H), 1.13−0.99 (m, 10H), 0.78 (d, J = 6.8 Hz, 6H), 0.28 (d, J = 6.8 Hz, 6H). 13C NMR (101 MHz, CDCl3) δ = 134.4 (d, J = 87.6 Hz), 132.5−132.3 (m), 131.0 (s), 130.7−130.4 (m), 127.9 (s), 127.9 (s), 127.8 (s), 125.4 (s), 43.3 (s), 40.2 (d, J = 65.9 Hz), 35.3 (s), 34.5 (s), 34.2 (s), 33.6 (s), 33.5 (s), 33.4 (s), 33.4 (s), 28.0 (s), 24.6 (s), 24.6 (s), 24.6 (s), 22.9 (s), 21.5 (s), 15.2 (s). HRMS (ESI+) Calcd for C40H57O2P2 [M + H+] 631.3834, found 631.3830. (RP ,RP )-(1,3-Phenylenebis(methylene))bis((−)-menthylphenylphosphine oxide), 5b. The specimen was obtained from Method A for 65 h. The ratio of crude 5b/5b′ was detected as >99:1 dr (estimated by 1H NMR spectra), and the pure compound was obtained as a white solid (39 mg, 62%, >99:1 dr) from flash chromatography (silica gel, petroleum ether/ethyl acetate = 1/6 as 31 eluent). [α]20 D = −155.23, (c = 0.19, CH2Cl2). mp 209.9−213.2 °C. P NMR (162 MHz, CDCl3) δ = 40.22 (s). 1H NMR (400 MHz, CDCl3) δ = 7.37 (t, J = 7.6 Hz, 4H), 7.33−7.26 (m, 2H), 7.25−7.21 (m, 4H), 6.83 (s, 1H), 6.67 (d, J = 7.2 Hz, 1H), 6.63−6.36 (m, 2H), 3.45−3.24 (m, 2H), 2.86 (dd, J = 14.3, 8.0 Hz, 2H), 1.97 (s, 4H), 1.85 (s, 2H), 1.64 (s, 6H), 1.35−1.26 (m, 4H), 0.95−0.83 (m, 10H), 0.69 (d, J = 6.0 Hz, 6H), 0.27 (d, J = 6.0 Hz, 6H). 13C NMR (100 MHz, CDCl3) δ = 133.7(d, J = 89.9 Hz,), 132.3 (s), 132.3 (s), 132.2 (s), 131.6 (s),131.5 (s), 130.7 (s), 130.6 (s), 130.5 (s), 128.0 (s), 127.9 (s), 127.61 (s), 43.4 (s), 41.0 (s), 40.4 (s), 35.8 (s), 35.4 (s), 35.2 (s), 34.3 (s), 33.2 (d, J = 13.0 Hz), 28.1 (s), 24.6 (d, J = 12.1 Hz), 22.6 (s), 21.4 (s), 15.2 (s). IR (KBr) ν/cm−1 2957, 1454, 1191, 701, 530. HRMS (ESI+) Calcd for C40H57O2P2 [M + H+] 631.3834, found 631.3829. (RP ,RP )-(1,4-Phenylenebis(methylene))bis((−)-menthylphenylphosphine oxide), 5c. The specimen was obtained from Method C for 23 h. The ratio of crude 5c/5c′ was detected as >99:1 dr (estimated by 1 H NMR spectra), and the pure compound was obtained as a white solid (45 mg, 72%, >99:1 dr) from recrystallization with petroleum ether−dichloromethane. mp 310.5−312.2 °C. 31P NMR (162 MHz, CDCl3) δ = 39.84 (s). 1H NMR (400 MHz, CDCl3) δ = 7.43 (t, J = 7.6 Hz, 4H), 7.36 (d, J = 7.2 Hz, 2H), 7.32−7.27 (m, 4H), 6.72 (s, 4H), 3.37 (t, J = 15.2 Hz, 2H), 2.93 (dd, J = 14.4, 7.2 Hz, 2H), 2.06− 1.91 (m, 8H), 1.74−1.63 (m, 6H), 1.42−1.31 (m, 4H), 0.97−0.92 (m, 8H), 0.76 (d, J = 6.8 Hz, 6H), 0.29 (d, J = 6.8 Hz, 6H). 13C NMR (101 MHz, CDCl3) δ = 134.2 (s), 133.3 (s), 130.8 (s), 130.5(s), 130.4 (s), 130.4 (s), 130.4−129.3 (m), 127.9 (s), 127.9 (s), 127.8 (s), 43.3 (s), 40.8 (s), 40.1 (s), 36.1 (s), 35.5 (s), 35.3 (s), 34.2 (s), 33.3 (s), 33.2 (s), 28.1 (s), 24.7 (s), 24.6 (s), 22.6 (s), 21.4 (s), 15.1 (s). HRMS (ESI+) Calcd for C40H57O2P2 [M + H+] 631.3834, found 631.3819.

(RP,RP)-(Pyridine-2,6-diylbis(methylene))bis((−)-Menthylphenylphosphine oxide), 5d. The specimen was obtained from Method A for 47 h. The ratio of crude 5d/5d′ was detected as >99:1 dr (estimated by 1H NMR spectra), and the pure compound was obtained as a white solid (58 mg, 92%, >99:1 dr) from flash chromatography (silica gel, petroleum ether/ethyl acetate = 1/5 as 31 eluent). [α]34 D = −18.0, (c = 0.10, CH2Cl2). mp 203.4−207.6 °C. P NMR (162 MHz, CDCl3) δ = 41.29 (s). 1H NMR (400 MHz, CDCl3) δ = 7.51−7.45 (m, 4H), 7.41−7.35 (m, 2H), 7.33−7.24 (m, 4H), 7.17 (t, J = 7.8 Hz, 1H), 6.88 (d, J = 7.8 Hz, 2H), 3.44 (dd, J = 16.4, 14.4 Hz, 2H), 3.32 (dd, J = 14.0, 10.0 Hz, 2H), 2.14−2.01 (m, 6H), 1.78− 1.64 (m, 6H), 1.46−1.25 (m, 4H), 1.09−0.98 (m, 3H), 0.96 (d, J = 6.4 Hz, 7H), 0.78 (d, J = 6.8 Hz, 6H), 0.37 (d, J = 6.8 Hz, 6H). 13C NMR (100 MHz, CDCl3) δ = 152.6 (s), 152.5 (s), 136.1 (s), 133.5 (d, J = 89.2 Hz), 130.8 (s), 130.7 (s), 130.6 (s), 127.8 (d, J = 11.1 Hz), 122.4 (s), 43.3 (d, J = 2.5 Hz), 40.6 (d, J = 66.4 Hz), 38.7 (d, J = 58.2 Hz), 35.3 (s), 34.3 (s), 33.2 (d, J = 13.3 Hz), 28.1 (s), 24.7 (d, J = 12.3 Hz), 22.7 (s), 21.5 (s), 15.3 (s). IR (KBr) ν/cm−1 2929, 1438, 1193, 745, 540. HRMS (ESI+) Calcd for C39H56NO2P2 [M + H+]:632.3786. Found: 632.3781. (R P ,R P )-(−)-Methylene-bis(((−)-menthyl)(phenyl)phosphine oxide), 5e. The specimen was obtained from Method A for 30 h. The ratio of crude 5e/5e′ was detected as >99:1 dr (estimated by 1H NMR spectra), and the pure compound was obtained as a white solid (49 mg, 91%, >99:1 dr) from flash chromatography (silica gel, petroleum ether/ethyl acetate = 1/3 as eluent). mp 151.3−153.4 °C. 31P NMR (162 MHz, CDCl3) δ = 41.32 (s). 1H NMR (400 MHz, CDCl3) δ = 7.78−7.66 (m, 4H), 7.57−7.41 (m, 6H), 2.27−2.10 (m, 2H), 1.97− 1.86 (m, 2H), 1.80−1.69 (m, 8H), 1.65 (d, J = 12.4 Hz, 6H), 1.34 (s, 2H), 1.22−1.11 (m, 2H), 1.05−1.94 (m, 4H), 0.90 (d, J = 6.4 Hz, 6H), 0.85 (d, J = 6.8 Hz, 4H), 0.42 (d, J = 6.8 Hz, 4H). 13C NMR (101 MHz, CDCl3) δ = 135.8 (d, J = 91.1 Hz), 131.0 (d, J = 2.6 Hz), 130.0 (d, J = 8.8 Hz), 128.3 (d, J = 11.1 Hz), 43.4 (d, J = 3.1), 41.5 (s), 40.8 (s), 35.6 (s), 34.3 (s), 33.2 (d, J = 13.6 Hz), 28.3 (s), 24.6 (d, J = 12.3 Hz), 22.6 (s), 21.5 (s), 15.3 (s), 15.1 (s), 14.6 (s), 1.0 (s). HRMS (ESI+) Calcd for C33H51O2P2 [M + H+] 541.3364, found 541.3363. (RP,RP)-Propane-1,3-diylbis((−)-menthylphenylphosphine oxide), 5f. The specimen was obtained from Method A, B for 60 h. The ratio of crude 5f/5f′ was detected as >99:1 dr (estimated by 1H NMR spectra), and the pure compound was obtained as a white solid (49 mg, 87%, >99:1 dr) from flash chromatography (silica gel, petroleum ether/ethyl acetate = 1/3 as eluent). [α]34 D = −67.5, (c = 0.12, CH2Cl2). mp 203.3−204.8 °C. 31P NMR (162 MHz, CDCl3) δ = 40.43 (s). 1H NMR (400 MHz, CDCl3) δ = 7.55−7.50 (m, 4H), 7.42−7.36 (m, 2H), 7.35−7.31 (m, 4H)2.15−1.96 (m, 7H), 1.91−1.75 (m, 4H), 1.75−1.56 (m, 5H), 1.48−1.34 (m, 2H), 1.34−1.16 (m, 4H), 1.02−0.96 (m, 2H), 0.91 (d, J = 6.0 Hz, 7H), 0.81 (d, J = 6.8 Hz, 6H), 0.27 (d, J = 6.8 Hz, 6H). 13C NMR (101 MHz, CDCl3) δ = 134.3 (s), 133.5 (s), 131.1 (s), 130.9 (s), 130.8 (s), 130.6 (s), 130.5 (s), 128.7 (s), 128.6 (s), 128.4 (s), 128.3 (s) 128.2 (s), 43.4 (d, J = 13.1 Hz), 41.5 (s), 40.9 (s), 35.4 (s), 34.4 (s), 34.3 (s), 33.4 (s), 28.5 (s), 28.4 (s), 27.9 (s), 27.8 (s), 25.0 (s), 24.8 (s), 24.7 (s), 24.6 (s), 22.8 (s), 22.7 (s), 21.8 (s), 21.7 (s), 15.3 (s), 15.2 (s), 15.1 (s) 14.7 (s). HRMS (ESI+) Calcd for C35H55O2P2 [M + H+] 569.3677, found 569.3676. (RP,RP)-Butane-1,4-diylbis((−)-menthylphenylphosphine oxide), 5g. The specimen was obtained from Method A, B for 90 h, The ratio of crude 5g/5g′ was detected as >99:1 dr (estimated by 1H NMR spectra), and the pure compound was obtained as a white solid (54 mg, 92%, >99:1 dr) from flash chromatography (silica gel, petroleum ether/ethyl acetate = 1/3 as eluent). mp 192.4−196.3 °C. 31P NMR (162 MHz, CDCl3) δ = 43.10 (s). 1H NMR (400 MHz, CDCl3) δ = 7.64−7.57 (m, 4H), 7.47−7.39 (m, 6H), 2.08−1.98 (m, 4H), 1.93− 1.76 (m, 4H), 1.73−1.54 (m, 10H), 1.31 (s, 2H), 1.22−1.11 (m, 4H), 1.03−0.94 (m, 3H), 0.91 (d, J = 6.4 Hz, 6H), 0.81 (d, J = 6.8 Hz, 6H), 0.31 (d, J = 6.8 Hz, 6H). 13C NMR (101 MHz, CDCl3) δ = 134.3 (d, J = 87.0 Hz), 130.9 (d, J = 2.0 Hz), 130.4 (d, J = 8.1 Hz), 128.3 (d, J = 11.1 Hz), 43.2 (d, J = 3.4 Hz), 40.9 (d, J = 66.5 Hz), 35.3 (s), 34.2 (s), 33.2 (d, J = 12.9 Hz), 28.2 (d, J = 2.8 Hz), 27.5 (d, J = 65.9 Hz), 24.6 (d, J = 11.9 Hz), 22.8 (s), 22.6 (s), 21.5 (s), 15.1 (s). HRMS (ESI+) Calcd for C36H57O2P2 [M + H+] 583.3834, found 583.3837. 9432

DOI: 10.1021/acs.joc.7b01413 J. Org. Chem. 2017, 82, 9425−9434

Article

The Journal of Organic Chemistry

22.4 (s), 21.4 (s), 15.7 (s), 15.3 (s). IR (KBr) ν/cm−1 2961, 2387, 1437, 1066, 733. HRMS (ESI+) Calcd for C27H42BP[M+] 408.3117, found 408.3104. (RP)-(−)-Menthyl 4-chlorobenzylphenylphosphine broane, 6d. The ratio of crude 6d/6d′ was detected as >99:1 dr (estimated by 1 H NMR spectra), and the compound was obtained from quenching with dilute HCl, extracting with ether and removing the solvent, as a white solid (69 mg, 90%, >99:1 dr), which was directly used for analysis without further purification. [α]34 D = +53.5, (c = 0.20, CH2Cl2). mp 111.8−119.2 °C. 31P NMR (162 MHz, CDCl3) δ = 26.03−25.52 (broad m). 1H NMR (400 MHz, CDCl3) δ 7.57 (t, J = 8.4 Hz, 2H), 7.47−7.33 (m, 3H), 7.01 (d, J = 8.4 Hz, 2H), 6.83−6.72 (m, 2H), 3.43 (dd, J = 13.6, 6.8 Hz, 1H), 3.31 (t, J = 14.4 Hz, 1H), 2.43−2.28 (m, 1H), 2.23−2.08 (m, 1H), 1.83−1.60 (m, 4H), 1.43−1.35 (m, 1H), 1.26 (m, 1H), 0.95 (d, J = 6.8 Hz, 2H), 0.87 (d, J = 6.8 Hz, 2H), 0.74 (d, J = 6.8 Hz, 2H). 0.07 (s, 1H). 13C NMR (101 MHz, CDCl3) δ 132.9 (d, J = 7.7 Hz), 132.4 (d, J = 3.6 Hz), 131.3 (d, J = 5.1 Hz), 131.2 (d, J = 4.0 Hz) 131.1 (d, J = 2.0 Hz), 128.5 (d, J = 9.4 Hz), 127.9 (s), 127.8 (s), 127.7 (s), 127.2 (s), 44.4 (s), 37.5 (s), 37.2 (s), 36.8 (s), 34.5 (s), 34.3 (s), 34.2 (s), 33.5 (d, J = 10.5 Hz), 28.8 (d, J = 2.9 Hz), 25.1 (d, J = 11.2 Hz), 22.4 (s), 21.4 (s), 15.7 (s). IR (KBr) ν/cm−1 2958, 2387, 1492, 1067, 735. HRMS (ESI+) Calcd for C23H31ClP[M − BH3 + H+] 373.1852, found 373.1855. (RP,RP)-1,3-bis((−)-Menthyl(phenyl)phosphanyl)methylbenzene broane, 6e. The ratio of crude 6e/6e′ was detected as >97:3 dr (estimated by 1H NMR spectra), and the pure compound was obtained as a white solid (90 mg, 72%, >99:1 dr) from flash chromatography (silica gel, petroleum ether/ethyl acetate = 4/1 as 31 P eluent). [α]34 D = +11.5, (c = 0.13, CH2Cl2). mp 66.1−68.2 °C. NMR (162 MHz, CDCl3) δ = 25.52 (broad s). 1H NMR (400 MHz, CDCl3) δ 7.47 (t, J = 8.4 Hz, 4H),7.43−7.36 (m, 2H), 7.35−7.28 (m, 4H), 6.65 (t, J = 8.0 Hz, 2H), 6.47 (dd, J = 7.6, 1.6 Hz, 2H),3.34 (dd, J = 13.6, 7.2 Hz, 2H), 3.18 (t, J = 14.0 Hz, 2H), 2.41−2.29 (m, 2H), 2.24−2.10 (m, 2H), 1.82−1.55 (m, 7H), 1.42−1.22 (m, 5H), 1.18− 1.02 (m. 3H), 0.96 (d,J = 6.8 Hz, 7H), 0.92−0.81 (m, 11H), 0.73(d, J = 6.4 Hz, 7H). 13C NMR (101 MHz, CDCl3) δ 133.1 (d, J = 7.6 Hz), 132.5 (dd, J = 5.1, 2.4 Hz), 131.9 (t, J = 7.6 Hz), 130.7 (s), 128.3 (s), 128.2 (s), 128.0 (s), 127.5 (s), 127.2 (s), 44.5 (s), 37.0(s), 36.9 (s), 36.7 (s), 34.7 (s), 34.4 (s), 34.3 (s), 33.4 (d, J = 10.5 Hz), 28.7 (d, J = 2.7 Hz), 25.1 (d, J = 11.2 Hz), 22.4 (s), 21.4 (s), 15.8 (s). HRMS (ESI+) Calcd for C40H57P2 [M − BH3 + H+] 599.3935, found 599.3940.

Experimental Procedure for Synthesis of Phosphine Boranes 6. To a stirred solution of 3 or 5 (0.2 mmol) in toluene (2 mL) was added oxalyl chloride (0.025 mL, 0.3 mmol) dropwise at room temperature under a nitrogen atmosphere. After 30 min, the solution was cooled to −65 °C, and the above solution of sodium borohydride/zinc chloride (0.2 mL, 0.4 mmol for sodium borohydride) was added dropwise. The mixture was stirred meanwhile wormed to room temperature, then was stirred at room temperature for 12 h. After quenched with dilute HCl (0.2 N, 5 mL) carefully, the mixture was extracted with ether (3 × 20 mL). The combined organic layer was dried over anhydrous magnesium sulfate. After removing the solvent in vacuo, the resulted solid was purified by column chromatography on silica gel (petroleum ether/ethyl acetate = 10/1) to afford the pure compound. (RP)-(−)-Menthyl benzylphenylphosphine broane, 6a. The ratio of crude 6a/6a′ was detected as 99:1 dr (estimated by 1H NMR spectra), and the pure compound was obtained as a white solid (57 mg, 81%, >99:1 dr) from flash chromatography (silica gel, petroleum ether/ethyl acetate = 6/1 as eluent). [α]34 D = +55.2, (c = 0.29, CH2Cl2). mp 169.2−171.7 °C. 31P NMR (162 MHz, CDCl3) δ = 25.83−25.28 (broad m). 1H NMR (400 MHz, CDCl3) δ = 7.57 (t, J = 8.4 Hz, 2H), 7.45−7.34 (m, 3H), 7.14−6.98 (m, 3H), 6.92−6.84 (m, 2H), 3.48 (dd, J = 13.6, 6.8 Hz, 1H), 3.34 (t, J = 14.0 Hz, 1H), 2.45−2.31 (m, 1H), 2.23−2.10 (m, 1H), 1.84−1.62 (m, 3H), 1.55 (s, 2H), 1.46−1.37 (m, 1H), 1.34−1.22 (m, 1H), 1.15−1.01 (m, 2H), 0.96 (d, J = 6.8 Hz, 2H), 0.78 (d, J = 6.8 Hz, 2H), 0.74 (d, J = 6.4 Hz, 2H). 13C NMR (101 MHz, CDCl3) δ = 132.9 (d, J = 8.1 Hz), 132.7 (d, J = 4.0 Hz), 130.8 (d, J = 3.0 Hz), 130.2 (d, J = 4.0 Hz), 130.1 (d, J = 5.1 Hz), 128.3 (d, J = 10.1 Hz), 128.1 (s), 127.7 (t, J = 3.0 Hz), 127.6 (s), 126.5 (d, J = 3.0 Hz), 44.4 (d, J = 2.0 Hz), 37.5 (s), 37.2 (s), 36.9 (s), 34.9 (s), 34.7 (s), 34.3 (d, J = 2.0 Hz), 33.5 (d, J = 10.4 Hz), 28.7 (d, J = 3.0 Hz), 25.1 (d, J = 11.1 Hz), 22.6 (s), 22.4 (s), 21.4 (s), 21.1 (s), 15.7 (s). IR (KBr) ν/cm−1 2959, 2392, 1454, 694. HRMS (ESI+) Calcd for C23H32P [M − BH3 + H+] 339.2242, found 339.2253. (RP)-(−)-Menthyl 4-methylbenzylphenylphosphine broane, 6b. The ratio of crude 6b/6b′ was detected as 96:4 dr (estimated by 1H NMR spectra), and the pure compound was obtained as a white solid (58 mg, 79%, >99:1 dr) from flash chromatography (silica gel, petroleum ether/ethyl acetate = 7/1 as eluent). [α]34 D = +50.0, (c = 0.16, CH2Cl2). mp 176.4−180.3 °C. 31P NMR (162 MHz, CDCl3) δ = 25.48−25.05 (broad m). 1H NMR (400 MHz, CDCl3) δ 7.58 (t, J = 8.4 Hz, 2H), 7.45−7.30 (m, 3H), 6.86 (d, J = 7.6 Hz, 2H), 6.75 (d, J = 6.8 Hz, 2H), 3.43 (dd, J = 14.0, 7.2 Hz, 1H), 3.32 (t, J = 14.4 Hz, 1H), 2.45−2.33 (m, 1H), 2.19 (s, 3H), 2.15−2.06 (m, 1H), 1.82−1.59 (m, 4H), 1.45−1.35 (m, 1H), 1.34−1.21 (m, 1H), 1.15−0.97 (m, 2H), 0.95 (t, J = 6.4 Hz, 4H), 0.86 (d, J = 7.2 Hz, 4H), 0.73 (d, J = 6.4 Hz, 3H), 0.65−0.35 (m, 1H). 13C NMR (101 MHz, CDCl3) δ 136.0 (d, J = 3.1 Hz), 132.9 (d, J = 7.6 Hz), 130.8 (d, J = 2.3 Hz), 129.9 (d, J = 4.4 Hz), 129.4 (d, J = 4.7 Hz), 128.4 (d, J = 2.0 Hz),128.4 (s), 128.3 (s), 128.2 (s),127.7 (s), 44.4 (s), 37.4 (s), 37.1 (s), 36.8 (s), 34.4 (s), 34.3 (d, J = 1.0 Hz), 34.01 (s), 33.4 (d, J = 10.4 Hz), 28.7 (d, J = 2.9 Hz), 25.1 (d, J = 11.1 Hz), 22.4 (s), 21.4 (s), 21.0 (s), 15.7 (s). HRMS (ESI+) Calcd for C24H36BPNa [M + Na+] 389.2545, found 389.2537. (RP)-(−)-Menthyl 4-tert-butylbenzylphenylphosphine broane, 6c. The ratio of crude 6c/6c′ was detected as 96:4 dr (estimated by 1H NMR spectra), and the pure compound was obtained as a white solid (68 mg, 83%, >99:1 dr) from flash chromatography (silica gel, petroleum ether/ethyl acetate = 6/1 as eluent). [α]34 D = +46.5, (c = 0.20, CH2Cl2). mp 147.6−150.3 °C. 31P NMR (162 MHz, CDCl3) δ = 25.24−24.86 (broad m). 1H NMR (400 MHz, CDCl3) δ 7.57 (t, J = 8.4 Hz, 2H),7.43−7.30 (m, 3H), 7.07 (d, J = 8.4 Hz, 2H), 6.81 (d, J = 6.8 Hz, 2H), 3.34 (dd, J = 14.0, 7.2 Hz, 1H), 3.33 (t, J = 14.4 Hz, 1H), 2.43−2.32 (m, 1H), 2.20−2.08 (m, 1H), 1.84−1.58 (m, 4H), 1.47− 1.37 (m, 1H), 1.21 (s, 9H), 1.13−1.04 (m, 2H), 0.95 (d, J = 6.8 Hz, 4H), 0.92−0.87 (m, 2H), 0.85 (d, J = 6.8 Hz, 4H), 0.74 (d, J = 6.4 Hz, 3H). 13C NMR (101 MHz, CDCl3) δ 149.32 (s), 132.9 (d, J = 7.6 Hz), 130.7 (d, J = 2.3 Hz), 129.7 (d, J = 4.0 Hz), 129.6 (d, J = 4.0 Hz),128.3 (d, J = 9.4 Hz), 127.8 (s), 124.7 (d, J = 2.4 Hz), 65.9 (s), 44.4 (s), 37.3 (s), 37.1 (s), 36.9 (s), 34.3 (s), 34.3 (s), 33.9 (s), 33.5 (d, J = 10.4 Hz), 31.2 (s), 28.7 (d, J = 2.8 Hz), 25.1 (d, J = 11.1 Hz),

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* Supporting Information S

The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acs.joc.7b01413. Additional experimental details; Computational data; Crystallographic information; Copies of 1H, 31P, and 13C NMR spectra (PDF) Crystal data for 3a (CIF)

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AUTHOR INFORMATION

Corresponding Author

*E-mail: [email protected]. ORCID

Chang-Qiu Zhao: 0000-0002-9016-8151 Author Contributions †

S.-Z.N. and Z.-Y.Z. contributed equally.

Notes

The authors declare no competing financial interest.

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ACKNOWLEDGMENTS The authors acknowledge the financial support of the Natural Science Foundation of China (Grant No. 20772055) and the 9433

DOI: 10.1021/acs.joc.7b01413 J. Org. Chem. 2017, 82, 9425−9434

Article

The Journal of Organic Chemistry

(12) A bidentate ligand QuinoxP: Imamoto, T.; Sugita, K.; Yoshida, K. J. Am. Chem. Soc. 2005, 127, 11934−11935. (13) (a) Katagiri, K.; Danjo, H.; Yamaguchi, K.; Imamoto, T. Tetrahedron 2005, 61, 4701−4707. (b) Haynes, R. K.; Lam, W. W.-L.; Yeung, L.-L. Tetrahedron Lett. 1996, 37, 4729−4732. (14) Sun, Y.-M.; Xin, N.-N.; Xu, Z.-Y.; Liu, L.-J.; Meng, F.-J.; Zhang, H.; Fu, B.-C.; Liang, Q.-J.; Zheng, H.-X.; Sun, L.-J.; Zhao, C.-Q.; Han, L.-B. Org. Biomol. Chem. 2014, 12, 9457−9465. (15) (a) Henderson, W. A.; Streuli, C. A. J. Am. Chem. Soc. 1960, 82, 5791−5794. (b) Ikuta, S.; Kebarle, P.; Bancroft, G. M.; Chan, T.; Puddephatt, R. J. J. Am. Chem. Soc. 1982, 104, 5899−5902. (c) Ikuta, S.; Kebarle, P. Can. J. Chem. 1983, 61, 97−102. (16) (a) An, G.; Seifert, C.; Li, G. Org. Biomol. Chem. 2015, 13, 1600−1617. (b) Seifert, C. W.; Paniagua, A.; White, G. A.; Cai, L.; Li, G. Eur. J. Org. Chem. 2016, 2016, 1714−1719. (c) Yang, B.; Shen, M.; Ji, X.; Xu, Z.; Sun, H.; Jiang, B.; Li, G. J. Org. Chem. 2016, 81, 2488− 2493. (d) Wu, J.; An, G.; Lin, S.; Xie, J.; Zhou, W.; Sun, H.; Pan, Y.; Li, G. Chem. Commun. 2014, 50, 1259−1261. (e) Kaur, P.; Pindi, S.; Wever, W.; Rajale, T.; Li, G. Chem. Commun. 2010, 46, 4330−4332. (17) (a) Wang, J.-P.; Nie, S.−Z.; Zhou, Z.-Y.; Ye, J.−J.; Wen, J.−H.; Zhao, C.-Q. J. Org. Chem. 2016, 81, 7644−7653. (b) Zhang, H.; Sun, Y.-M.; Yao, L.; Ji, S.-Y.; Zhao, C.-Q.; Han, L.-B. Chem. - Asian J. 2014, 9, 1329−1333. (18) (a) Rajendran, K. V.; Gilheany, D. G. Chem. Commun. 2012, 48, 817−819. (b) Rajendran, K. V.; Nikitin, K. V.; Gilheany, D. G. J. Am. Chem. Soc. 2015, 137, 9375−9381. (c) Al Sulaimi, S. S.; Rajendran, K. V.; Gilheany, D. G. Eur. J. Org. Chem. 2015, 2015, 5959−5965. (19) (a) Marsi, K. L. J. Org. Chem. 1974, 39, 265. (b) Wu, H.-C.; Yu, J.-Q.; Spencer, J. B. Org. Lett. 2004, 6, 4675−4678. (20) On proton NMR spectrum, the doublet peaks at 6.86 (J = 460.0 Hz) and 7.04 ppm (J = 459.6 Hz) were observed for RP-1a and SP-1a′, respectively. The two single peaks of 1a and 1a′ were respectively located at 33.3 and 28.0 ppm on 31P NMR spectrum. (21) Vedejs, E.; Donde, Y. J. Org. Chem. 2000, 65, 2337−2343. (22) The CH2 moiety of benzyl located at 3.51 (dd)/3.04 (dd) and 3.33 (dd)/2.62 (dd) ppm on proton NMR spectrum for 3a and 3a′, respectively. For the reaction of 1a, 3a′ was not detected on both proton and 31P NMR spectrum. (23) The reaction of 1a/1a′ with methyl iodide to form 3j/3j′ has the two signals at 41.3 and 42.9 ppm on 31P NMR spectrum. Optically pure 1a and methyl iodide only afforded the signal at 41.3 ppm that was ascribed to 3j.

Natural Science Foundation of Shandong Province (Grant No. ZR2014BP007 and ZR2016BM18)

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DOI: 10.1021/acs.joc.7b01413 J. Org. Chem. 2017, 82, 9425−9434