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Short Note

2,2-Bis(phenylselanyl)-1-(p-tolyl)vinyl 2-Oxo-2-(p-tolyl)acetate

by
Shintaro Kodama
1,
Vu Thai Hung
1,
Tomokazu Saeki
1,
Kei Mihara
1,
Yuki Yamamoto
1,
Motohiro Sonoda
2,
Akihiro Nomoto
1 and
Akiya Ogawa
1,*
1
Department of Applied Chemistry, Graduate School of Engineering, Osaka Prefecture University, 1-1 Gakuen-cho, Nakaku, Sakai, Osaka 599-8531, Japan
2
Department of Applied Biosciences, Graduate School of Life and Environmental Sciences, Osaka Prefecture University, 1-1 Gakuen-cho, Nakaku, Sakai, Osaka 599-8531, Japan
*
Author to whom correspondence should be addressed.
Molbank 2021, 2021(4), M1283; https://doi.org/10.3390/M1283
Submission received: 25 August 2021 / Accepted: 24 September 2021 / Published: 28 September 2021
(This article belongs to the Section Organic Synthesis)
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Versions Notes

Abstract

:
2,2-Bis(phenylselanyl)-1-(p-tolyl)vinyl 2-oxo-2-(p-tolyl)acetate was synthesized via the reaction of p-tolylacetylene with diphenyl diselenide and benzoyl peroxide in benzene under atmospheric conditions. The molecular structure of the synthesized compound was evaluated using single-crystal X-ray analysis and spectral analyses. The process reported here provides a rare example of the direct and selective transformation of a terminal alkyne to the corresponding geminal diseleno-substituted alkene.

1. Introduction

Atomically efficient and selective addition reaction of heteroatom compounds to carbon−carbon unsaturated bonds is one of the most valuable synthetic reactions [1,2,3,4,5,6,7,8,9,10,11,12]. The addition of heteroatom compounds to alkynes affords the corresponding alkenyl heteroatoms, which are typically present not only in synthetic intermediates but also in a variety of natural products and functional molecules [13,14,15,16,17,18].
During the course of our study on the simultaneous introduction of different heteroatom groups into alkynes [19,20,21,22,23,24,25,26], we successfully developed a binary system composed of benzoyl peroxide [(PhCOO)2; BPO] and diphenyl diselenide [(PhSe)2] for the selective selenation of alkynes [26]. Specifically, in the case of internal alkynes, the stereoselective benzoyloxyselenation reaction yielded the corresponding β-(benzyloxy)alkenyl selenides, whereas terminal alkynes were converted to alkynyl selenides via a C(sp)–H substitution reaction with (PhSe)2 (Scheme 1). Herein, we report a unique multi-coupling reaction of a terminal alkyne (p-tolylacetylene, 1a), BPO, and (PhSe)2 to produce a novel 1,2-diketone compound (2a) containing a geminal diseleno-substituted alkene moiety (see, Scheme 2).

2. Results and Discussion

During the reaction of p-tolylacetylene (1a) with (PhSe)2 (1 equiv) and BPO (2 equiv) in benzene, the title coupling product, 2a, was formed in 60% yield. The structure of this product was determined using X-ray diffraction (Scheme 2 and Figure 1) and several spectral analyses (the 1H, 13C{1H} and 77Se{1H} NMR spectra of 2a are included in the Supplementary Materials). As indicated in Scheme 2, the molecular structure of 2a consists of one molecule of (PhSe)2 and two molecules of the terminal alkyne 1a.
The multi-coupling reaction of 1a, BPO, and (PhSe)2 was further evaluated under various reaction conditions (Table 1). Increasing the amount of (PhSe)2 did not induce a significant increase in the yield of 2a, whereas byproducts 3a and 4a were formed (entry 1 vs. entry 2). Prolonging the reaction time was also ineffective in improving the yield of 2a (entry 1 vs. entry 3). When the amount of (PhSe)2 was reduced to 0.10 mmol and an excess amount (0.60 mmol) of BPO was introduced, 3a was formed as the primary reaction product (entry 4). Among the solvents used, benzene produced the most encouraging results (entry 1 vs. entries 5−7). The yield of 2a was slightly improved by reducing the amount of the benzene solvent used (entry 8). When the reaction was conducted using concentrated benzene solvent (heated at 80 °C without cooling water), the yield of 2a was improved to 63% (entry 9). However, a further increase in the reaction temperature to 100 °C decreased the yield of 2a (entries 10 and 11).
To evaluate the formation mechanism of 2a, the reaction of alkynyl selenide 3a was attempted using equimolar amounts of (PhSe)2 and BPO to produce the coupling product 2a in a 61% yield (Scheme 3). The result suggests that alkynyl selenide 3a acts as an intermediate during the formation of 2a. It should be noted that 2a possesses an α-keto ester moiety, which may be formed during the oxidation of the alkynyl ether moiety using molecular oxygen (O2). Wille et al. previously reported the oxidation of alkynes (e.g., PhC≡CPh) to produce 1,2-diketones (e.g., PhC(=O)–C(=O)Ph) in the presence of O2, in a process initiated by the thiyl radical (PhS•). More specifically, the thiylperoxyl radical (PhSOO•), derived from PhS• and O2, acted as an initiator during the oxidation reaction [27]. Therefore, we assume that the C≡C triple bond in the alkynyl ether intermediate 6a (or 4a), a precursor to 2a, underwent oxidation with O2 in the presence of the selenoperoxyl radical PhSeOO•, which acts as an initiator. Although this process has several potential reaction routes, one of the most promising is given in Scheme 4. The thermal decomposition of BPO generates a benzoyloxy radical, which attacks 3a to produce alkynyl benzoate, 4a. The subsequent electrophilic reaction of 3a with 4a in the presence of 5a produced 6a along with benzoic acid anhydride. Notably, this reaction provides a rare example of the direct and selective transformation of a terminal alkyne to the corresponding geminal diseleno-substituted alkene [28,29,30].

3. Experimental

3.1. General

1H-NMR spectra were obtained using a JEOL JMN-ECX400 (400 MHz) FT NMR system (JEOL, Tokyo, Japan), in which CDCl3 was employed as the deuterated solvent and Me4Si was used as an internal standard. 13C{1H} NMR spectra were obtained using a JEOL JNM-ECX400 (100 MHz) FT NMR system (JEOL, Tokyo, Japan). The 77Se{1H} NMR spectrum was obtained using a JEOL JNM-ECX400 (76 MHz) FT NMR system (JEOL, Tokyo, Japan). Unless otherwise stated, all reagents and solvents were purchased from chemical companies and used without further purification.

3.2. Synthesis of 2,2-Bis(phenylselanyl)-1-(p-tolyl)Vinyl 2-Oxo-2-(p-tolyl)Acetate (2a)

Initially, BPO (0.20 mmol), (PhSe)2 (0.20 mmol), p-tolylacetylene (1a) (0.20 mmol), and benzene (3 mL) were added to a 10 mL round-bottomed flask. The resultant mixture was then heated at 80 °C for 16 h in the dark, under atmospheric conditions. Once the reaction was complete, the reaction mixture was treated with saturated aqueous sodium thiosulfate. The product was then extracted using ethyl acetate, and the resultant combined organic layer was washed using saturated aqueous sodium bicarbonate. The organic layer was neutralized with aqueous HCl (0.1 N). Subsequently, the combined extracts were dried using MgSO4. Filtration and concentration in vacuo yielded the crude product, which was subsequently purified using GPC (eluent CHCl3) to obtain 2a (35.4 mg, 60% yield) as a pale-yellow solid. Mp 65.0–66.0 °C; 1H-NMR (CDCl3) δ 7.97 (d, J = 8.2 Hz, 2H), 7.52 (d, J = 7.8 Hz, 2H), 7.37 (dd, J = 8.5, 1.1 Hz, 2H), 7.27–7.17 (m, 12H), 2.41 (s, 3H), 2.36 (s, 3H); 13C{1H} NMR (CDCl3) δ 184.4, 160.9, 150.8, 146.4, 139.9, 134.8, 132.3, 131.4, 131.1, 130.5, 130.0, 129.9, 129.6, 129.2, 128.81, 128.77, 128.7, 128.0, 127.3, 113.7, 21.9, 21.5; 77Se{1H} NMR (CDCl3) δ 452, 431; IR (KBr, cm−1): 2360, 2331, 1748, 1683, 1604, 1577, 1475, 1438, 1151, 954, 735; MS (FAB): m/z = 592 [M]+. HRMS (ESI) analysis of 2a also showed m/z 468.9585 attributed to the sodium ion adduct of (PhSe)2CHC(=O)(C6H4-p-CH3) (calcd m/z: 468.9586) generated via decomposition of the thermally unstable 1,2-diketone moiety of 2a during the analysis, which supports the identification of 2a.

3.3. X-ray Diffraction Studies

An X-ray crystallographic measurement was carried out on a Rigaku RAXIS-RAPID diffractometer with Mo-Kα radiation at 123 K. Of 39479 reflections collected, 5743 were unique (Rint = 0.0465). An empirical absorption correction was applied, which resulted in transmission factors ranging from 0.513 to 0.942. The data were corrected for Lorentz and polarization effects. The structure of 2a was solved by direct methods and expanded using Fourier techniques. The non-hydrogen atoms were refined anisotropically, and hydrogen atoms were refined using the riding model. All calculations were performed with the CrystalStructure [31] crystallographic software package except for refinements, which was performed using SHELXL Version 2014/7 [32].
Crystallographic data: formula weight = 590.44; monoclinic; space group P21/n; a = 9.62321(17) Å, b = 5.73648(10) Å, c = 45.1254(8) Å; V = 2490.50(8) Å3; Z = 4; ρcalcd = 1.575 g cm−3; total reflections collected = 39479; GOF = 1.054; R1 = 0.0264; wR2 = 0.0672. Crystallographic data have been deposited with Cambridge Crystallographic Data Centre (CCDC-2104238). These data can be obtained free of charge via http://www.ccdc.cam.ac.uk/conts/retrieving.html (accessed date: 19 August 2021) (or from the CCDC, 12 Union Road, Cambridge CB2 1EZ, UK; Fax: +44 1223 336033; E-mail: deposit@ccdc.cam.ac.uk).

4. Conclusions

A unique multi-coupling reaction of the terminal alkyne 1a, (PhSe)2, and BPO was observed, the mechanism of which was based on an oxidation process. We believe that the results presented here provide a novel and facile route for the synthesis of geminal diseleno-substituted alkenes.

Supplementary Materials

The following are available: Figure S1. 1H-NMR spectrum (CDCl3, 400 MHz) of compound 2a. Figure S2. 13C{1H} NMR spectrum (CDCl3, 100 MHz) of compound 2a. Figure S3. 77Se{1H} NMR spectrum (CDCl3, 76 MHz) of compound 2a.

Author Contributions

Investigation, S.K., V.T.H., T.S., K.M., Y.Y., M.S., A.N. and A.O.; Experiment, T.S., K.M. and Y.Y.; resources, S.K., A.N. and A.O.; writing—original draft preparation, S.K.; writing—review and editing, S.K., Y.Y., A.N. and A.O.; funding acquisition, S.K., A.N. and A.O. All authors have read and agreed to the published version of the manuscript.

Funding

This work was partly supported by JSPS KAKENHI Grant Numbers JP21H01977, JP19H02791, and JP19H02756, from the Ministry of Education, Culture, Sports, Science and Technology, Japan.

Institutional Review Board Statement

Not applicable.

Informed Consent Statement

Not applicable.

Data Availability Statement

The data presented in this study are available in the article and in its Supplementary Materials.

Acknowledgments

A part of this work was conducted in NAIST, supported by Nanotechnology Platform Program (Synthesis of Molecules and Materials) of the Ministry of Education, Culture, Sports, Science and Technology (MEXT), Japan.

Conflicts of Interest

The authors declare no conflict of interest.

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Molbank 2021 m1283 sch001 550
Scheme 1. Selective selenation of alkynes based on a BPO/(PhSe)2 binary system.
Scheme 1. Selective selenation of alkynes based on a BPO/(PhSe)2 binary system.
Molbank 2021 m1283 sch001
Molbank 2021 m1283 sch002 550
Scheme 2. Synthesis of 2a through the reaction of 1a with (PhSe)2 and BPO.
Scheme 2. Synthesis of 2a through the reaction of 1a with (PhSe)2 and BPO.
Molbank 2021 m1283 sch002
Molbank 2021 m1283 g001 550
Figure 1. Crystal structure of 2a with numbered atoms. Ellipsoids are shown at the 50% probability level. Selected interatomic distances (Å) and angles (deg): Se1−C1, 1.9178(17); Se1−C10, 1.916(2); Se2−C1, 1.9021(19); Se2−C16, 1.9188(19); O1−C2, 1.420(2); O1−C22, 1.360(2); O2−C22, 1.195(2); O3−C23, 1.215(2); C1−C2, 1.338(3); C2−C3, 1.482(3); C22−C23, 1.546(3); C23−C24, 1.478(3); C1−Se1−C10, 99.28(8); C1−Se2−C16, 101.23(8); C2−O1−C22, 116.88(14); Se1−C1−Se2, 120.61(10); Se1−C1−C2, 120.87(14); Se2−C1−C2, 118.38(13); O1−C2−C1, 119.30(16); O1−C2−C3, 111.41(15); C1−C2−C3, 129.04(17); O1−C22−O2, 125.80(17); O1−C22−C23, 109.00(15); O2−C22−C23, 125.14(17); O3−C23−C22, 117.29(16); O3−C23−C24, 123.59(17); C22−C23−C24, 119.09(16).
Figure 1. Crystal structure of 2a with numbered atoms. Ellipsoids are shown at the 50% probability level. Selected interatomic distances (Å) and angles (deg): Se1−C1, 1.9178(17); Se1−C10, 1.916(2); Se2−C1, 1.9021(19); Se2−C16, 1.9188(19); O1−C2, 1.420(2); O1−C22, 1.360(2); O2−C22, 1.195(2); O3−C23, 1.215(2); C1−C2, 1.338(3); C2−C3, 1.482(3); C22−C23, 1.546(3); C23−C24, 1.478(3); C1−Se1−C10, 99.28(8); C1−Se2−C16, 101.23(8); C2−O1−C22, 116.88(14); Se1−C1−Se2, 120.61(10); Se1−C1−C2, 120.87(14); Se2−C1−C2, 118.38(13); O1−C2−C1, 119.30(16); O1−C2−C3, 111.41(15); C1−C2−C3, 129.04(17); O1−C22−O2, 125.80(17); O1−C22−C23, 109.00(15); O2−C22−C23, 125.14(17); O3−C23−C22, 117.29(16); O3−C23−C24, 123.59(17); C22−C23−C24, 119.09(16).
Molbank 2021 m1283 g001
Molbank 2021 m1283 sch003 550
Scheme 3. Synthesis of 2a via the reaction of 3a with (PhSe)2 and BPO.
Scheme 3. Synthesis of 2a via the reaction of 3a with (PhSe)2 and BPO.
Molbank 2021 m1283 sch003
Scheme 4. Possible pathway for the multi-coupling reaction.
Table
Table 1. Optimization of the reaction conditions for the synthesis of 2a.
Table 1. Optimization of the reaction conditions for the synthesis of 2a.
Molbank 2021 m1283 i001
Molbank 2021 m1283 i001
Entry1a/(PhSe)2/BPO SolventConditionYields (%) a
(mmol)2a3a4a
10.20/0.20/0.40Benzene80 °C, 16 h48––
20.20/0.40/0.40Benzene80 °C, 16 h43255
30.20/0.2/0.40Benzene80 °C, 24 h40232
40.30/0.10/0.60Benzene80 °C, 24 hTrace48–
5 b,c0.20/0.20/0.40Et2O80 °C, 16 h22721
60.20/0.20/0.40Toluene80 °C, 16 h9––
70.20/0.20/0.40THF80 °C, 16 hN.D.1116
80.20/0.20/0.40Benzene (1 mL)80 °C, 16 h51N.D.6
9 b,c0.20/0.20/0.40Benzene (1 mL)80 °C, 16 h63N.D.6
100.20/0.20/0.40Benzene 100 °C, 16 h643Trace
110.20/0.20/0.40Benzene (1 mL)100 °C, 16 h27N.D.7
a Determined by 1H-NMR; b no cooling water used; c majority of the solvent was distilled out during the initial stages of the reaction, and the reaction proceeded under essentially neat conditions.
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MDPI and ACS Style

Kodama, S.; Hung, V.T.; Saeki, T.; Mihara, K.; Yamamoto, Y.; Sonoda, M.; Nomoto, A.; Ogawa, A. 2,2-Bis(phenylselanyl)-1-(p-tolyl)vinyl 2-Oxo-2-(p-tolyl)acetate. Molbank 2021, 2021, M1283. https://doi.org/10.3390/M1283

AMA Style

Kodama S, Hung VT, Saeki T, Mihara K, Yamamoto Y, Sonoda M, Nomoto A, Ogawa A. 2,2-Bis(phenylselanyl)-1-(p-tolyl)vinyl 2-Oxo-2-(p-tolyl)acetate. Molbank. 2021; 2021(4):M1283. https://doi.org/10.3390/M1283

Chicago/Turabian Style

Kodama, Shintaro, Vu Thai Hung, Tomokazu Saeki, Kei Mihara, Yuki Yamamoto, Motohiro Sonoda, Akihiro Nomoto, and Akiya Ogawa. 2021. "2,2-Bis(phenylselanyl)-1-(p-tolyl)vinyl 2-Oxo-2-(p-tolyl)acetate" Molbank 2021, no. 4: M1283. https://doi.org/10.3390/M1283

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