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Synlett 2012; 23(9): 1384-1388
DOI: 10.1055/s-0031-1291015
letter
© Georg Thieme Verlag Stuttgart · New York

Microwave-Assisted Regiospecific Synthesis of Pseudohalohydrin Esters

Mirna El Khatib
a   Center for Heterocyclic Compounds, Department of Chemistry, University of Florida, Gainesville, FL 32611-7200, USA, Email: katritzky@chem.ufl.edu
,
Mohamed Elagawany
a   Center for Heterocyclic Compounds, Department of Chemistry, University of Florida, Gainesville, FL 32611-7200, USA, Email: katritzky@chem.ufl.edu
b   Department of Pharmaceutical Organic Chemistry, Faculty of Pharmacy, Zagazig University, Zagazig 44519, Egypt
c   Department of Organic Chemistry, College of Pharmacy, Misr University for Science and Technology, Al-Motamayez District, P.O. Box 77, 6th of October City, Egypt
,
Ekaterina Todadze
a   Center for Heterocyclic Compounds, Department of Chemistry, University of Florida, Gainesville, FL 32611-7200, USA, Email: katritzky@chem.ufl.edu
,
Levan Khelashvili
a   Center for Heterocyclic Compounds, Department of Chemistry, University of Florida, Gainesville, FL 32611-7200, USA, Email: katritzky@chem.ufl.edu
,
Said A. El-Feky
b   Department of Pharmaceutical Organic Chemistry, Faculty of Pharmacy, Zagazig University, Zagazig 44519, Egypt
,
Alan R. Katritzky*
a   Center for Heterocyclic Compounds, Department of Chemistry, University of Florida, Gainesville, FL 32611-7200, USA, Email: katritzky@chem.ufl.edu
d   Department of Chemistry, King Abdulaziz University, Jeddah 21589, Saudi Arabia
› Author Affiliations
Further Information

Publication History

Received: 06 January 2012

Accepted after revision: 22 February 2012

Publication Date:
14 May 2012 (online)

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Abstract

N-Acylbenzotriazoles react regiospecifically with epoxides under palladium catalysis to give novel β-(benzotriazol-1-yl)ethyl esters (52–87%) constituting halohydrin ester surrogates.

Key words

regioselectivity - catalysis - palladium - esters - ring opening

Supporting Information

    for this article is available online at http://www.thieme-connect.com/ejournals/toc/synlett.
  • Supporting Information
 

  • References

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  • 36 General Procedure for the Preparation of β-(Benzotriazol-1-yl)ethyl Esters 4 and Alcohol 5a To a mixture of the N-acylbenzotriazole 1 (0.20 mmol) and Pd(PPh3)4 (23.11 mg, 10 mol%) in a microwave tube was added epoxide 3 (1.5 equiv). The mixture was stirred at 130 °C and 50 W for 30 min (N-aroylbenzotriazoles) to 60 min (N-alkylbenzotriazoles). The residue was dissolved in MeOH and purified by silica gel column chromatography to obtain the corresponding hydrin esters 4
  • 37 2-(1H-Benzotriazol-1-yl)-1-phenylethyl 4-ethylbenzoate (4a) Purified by gradient silica gel column chromatography (hexanes to hexanes–EtOAc = 7:3) to obtain a yellow oil, (87%). 1H NMR (300 MHz, CDCl3): δ = 7.83 (d, J = 8.1 Hz, 1 H), 7.69 (d, J = 8.1 Hz, 1 H), 7.27–7.14 (m, 10 H), 7.06–7.01 (m, 1 H), 6.29–6.25 (m, 1 H), 5.00–4.86 (m, 2 H), 2.48 (q, J = 7.4 Hz, 2 H), 1.03 (t, J = 7.5 Hz, 3 H). 13C NMR (75 MHz, CDCl3): δ = 165.3, 150.3, 136.7, 133.4, 129.9, 128.9, 128.0, 127.4, 126.3, 125.7, 123.9, 120.0, 109.3, 74.3, 52.8, 29.0, 15.2. HRMS: m/z calcd for C23H22N3O2 [M + H]+: 372.1707; found: 372.1703
  • 38 2-(1H-Benzotriazol-1-yl)-1,2-diphenylethyl 4-Ethylbenzoate (4b) Purified by gradient silica gel column chromatography (hexanes to hexanes–CH2Cl2 = 3:2, then hexanes–CH2Cl2 = 1:1) to obtain beige microcrystals (62%); mp 109.0–110.0 °C. 1H NMR (300 MHz, CDCl3): δ = 8.09 (dd, J = 8.3, 1.4 Hz, 1 H), 7.68–7.60 (m, 2 H), 7.54–7.47 (m, 1 H), 7.45–7.30 (m, 6 H), 7.27–7.20 (m, 6 H), 7.14–7.11 (m, 2 H), 6.34 (dd, J = 9.2, 1.4 Hz, 1 H), 2.82–2.73 (m, 1 H), 2.65 (q, J = 7.5 Hz, 2 H), 1.35–1.28 (m, 2 H), 1.22 (td, J = 7.8, 2.1 Hz, 3 H). 13C NMR (75 MHz, CDCl3): δ = 165.0, 149.9, 136.8, 134.6, 133.3, 130.2, 129.6, 128.8, 128.7, 128.7, 128.6, 128.5, 128.4, 128.2, 128.0, 127.7, 127.3, 127.2, 126.8, 125.9, 123.9, 120.1, 109.6, 76.8, 67.4, 28.8, 15.1. HRMS: m/z calcd for C29H26N3O2 [M + H]+: 448.2020; found: 448.2022
  • 39 1-{1H-Benzo[d][1,2,3]triazol-1-yl}hexan-2-yl 3-Phenylpropanoate (4c) Purified by gradient silica gel column chromatography (hexanes to hexanes–EtOAc = 4:1) to obtain a yellow oil (72%). 1H NMR (300 MHz, CDCl3): δ = 8.05–8.01 (m, 1 H), 7.49–7.42 (m, 2 H), 7.36–7.31 (m, 1 H), 7.29–7.07 (m, 5 H), 5.28–5.21 (m, 1 H), 4.74 (dd, J = 14.6, 4.8 Hz, 1 H), 4.69 (dd, J = 14.5, 6.1 Hz, 1 H), 2.97–2.40 (m, 4 H), 1.59–1.52 (m, 2 H), 1.30–1.19 (m, 4 H), 0.83 (t, J = 7.0 Hz, 3 H). 13C NMR (75 MHz, CDCl3): δ = 172.4, 145.9, 140.27, 133.7, 128.6, 128.4, 127.7, 126.5, 124.2, 120.2, 109.7, 72.5, 50.9, 35.9, 31.5, 30.9, 27.3, 22.6, 14.1
  • 40 2-{1H-Benzo[d][1,2,3]triazol-1-yl}-1-phenylethyl 1-Naphthoate (4d) Purified by gradient silica gel column chromatography (hexanes to hexanes–EtOAc = 9.3:0.7) to obtain a white solid (62%); mp 62.0–63.0 °C. 1H NMR (300 MHz, CDCl3): δ = 8.60–8.56 (m, 1 H), 8.09–7.97 (m, 3 H), 7.85–7.79 (m, 1 H), 7.50–7.26 (m, 11 H), 6.58 (dd, J = 7.5, 4.7 Hz, 1 H), 5.19 (dd, J = 14.6, 7.5 Hz, 1 H), 5.11 (dd, J = 14.6, 4.7 Hz, 1 H). 13C NMR (75 MHz, CDCl3): δ = 166.1, 146.0, 136.9, 134.0, 133.9, 133.6, 131.4, 130.6, 129.2, 128.7, 128.1, 127.7, 126.6, 126.5, 125.7, 124.6, 124.1, 120.3, 109.5, 74.7, 53.1. Anal. Calcd for C25H19N3O2: C, 76.32; H, 4.87; N, 10.68. Found: C, 75.97; H, 5.31; N, 10.45
  • 41 1-{1H-Benzo[d][1,2,3]triazol-1-yl}hexan-2-yl 1-Naphthoate (4e) Purified by gradient silica gel column chromatography (hexanes to EtOAc–hexanes = 9.3:0.7) to obtain a yellow oil (73%). 1H NMR (300 MHz, CDCl3): δ = 8.64–8.59 (m, 1 H), 8.02–7.89 (m, 3 H), 7.79–7.75 (m, 1 H), 7.51–7.17 (m, 6 H), 5.61–5.53 (m, 1 H), 4.88 (d, J = 5.3 Hz, 2 H), 1.78–1.70 (m, 2 H), 1.51–1.22 (m, 4 H), 0.81 (t, J = 7.2 Hz, 3 H). 13C NMR (75 MHz, CDCl3): δ = 166.8, 146.1, 133.9, 133.7, 131.5, 130.5, 128.7, 128.0, 127.6, 126.5, 126.4, 125.7, 124.6, 124.1, 120.2, 109.9, 72.8, 51.0, 31.7, 27.6, 22.6, 14.1. Anal. Calcd for C69H73N9O8: C, 71.67; H, 6.36; N, 10.90. Found: C, 71.53; H, 6.38; N, 10.93
  • 42 2-{1H-Benzo[d][1,2,3]triazol-1-yl}-1-phenylethyl 4-Nitrobenzoate (4f) Purified by gradient silica gel column chromatography (hexanes to hexanes–EtOAc = 9:1) to obtain a yellow oil (70%). 1H NMR (300 MHz, CDCl3): δ = 8.31–8.11 (m, 7 H), 7.52–7.34 (m, 5 H), 6.44 (dd, J = 8.4, 3.6 Hz, 1 H), 4.82 (dd, J = 12.0, 8.4 Hz, 1 H), 4.71(dd, J =12.2, 3.8 Hz, 1 H). 13C NMR (75 MHz, CDCl3): δ = 164.5, 164.0, 151.0, 135.6, 135.2, 135.1, 131.1, 131.0, 129.5, 129.3, 126.9, 123.9, 75.1, 67.3
  • 43 2-(1H-Benzotriazol-1-yl)-1-phenylethyl Benzoate (4g) Purified by gradient silica gel column chromatography (hexanes to hexanes–EtOAc = 9:1) to obtain a yellow oil (75%). 1H NMR (300 MHz, CDCl3): δ = 8.02–7.93 (m, 3 H), 7.55–7.27 (m, 11 H), 6.46 (dd, J = 7.5, 4.8 Hz, 1 H), 5.15 (dd, J = 14.5, 7.3 Hz, 1 H), 5.07 (dd, J = 14.5, 4.8, 1 H). 13C NMR (75 MHz, CDCl3): δ = 165.4, 145.9, 136.8, 133.6, 129.9, 129.5, 129.2, 129.1, 128.6, 127.6, 126.5, 124.1, 120.2, 109.4, 74.7, 52.9. HRMS: m/z calcd for C21H18N3O2 [M + H]+: 344.1394; found: 344.1384
  • 44 1-{1H-Benzo[d][1,2,3]triazol-1-yl}hexan-2-yl Benzoate (4h) Purified by gradient silica gel column chromatography (hexanes to hexanes–EtOAc = 9:1) to obtain a yellow oil (76%). 1H NMR (300 MHz, CDCl3): δ = 8.03–8.00 (m, 1 H), 7.91–7.88 (m, 2 H), 7.55–7.49 (m, 2 H), 7.40–7.28 (m, 4 H), 5.55–5.48 (m, 1 H), 4.90 (d, J = 5.2 Hz, 2 H), 1.76–1.67 (m, 2 H), 1.47–1.26 (m, 4 H), 0.85 (t, J = 7.2 Hz, 3 H). 13C NMR (75 MHz, CDCl3): δ = 166.1, 146.1, 133.7, 133.5, 129.9, 129.7, 128.6, 127.6, 124.1, 120.2, 109.9, 72.9, 50.9, 31.5, 27.5, 22.6, 14.0. HRMS: m/z calcd for C19H22N3O2 [M + H]+: 324.1707; found: 324.1719
  • 45 1-{1H-Benzo[d][1,2,3]triazol-1-yl}hexan-2-yl 2-[(3R,5R,7R)-Adamantan-1-yl]acetate (4i) Purified by gradient silica gel column chromatography (hexanes to hexanes–EtOAc = 9.3:0.7) to obtain a yellow oil (52%). 1H NMR (300 MHz, CDCl3): δ = 8.00–7.97 (m, 1 H), 7.56 (d, J = 8.4 Hz, 1 H), 7.47–7.41 (m, 1 H), 7.33–7.28 (m, 1 H), 5.27–5.19 (m, 1 H), 4.72–4.69 (m, 2 H), 2.05–1.88 (m, 3 H), 1.84–1.80 (m, 2 H), 1.63–1.55 (m, 8 H), 1.49–1.46 (m, 2 H), 1.37–1.18 (m, 8 H), 0.82 (t, J = 7.0 Hz, 3 H). 13C NMR (75 MHz, CDCl3): δ = 171.3, 146.0, 133.8, 127.7, 124.1, 120.2, 109.9, 71.9, 50.9, 49.0, 42.5, 42.4, 36.9, 36.8, 32.9, 31.7, 28.8, 28.7, 27.5, 22.6, 14.1. HRMS: m/z calcd for C24H33N3O2Na [M + Na]+: 418.2465; found: 418.2480
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  • 47 1-(1H-Benzotriazol-1-yl)hexan-2-ol (5a) Purified by gradient silica gel column chromatography (hexanes to EtOAc–hexanes = 4:1) to obtain a yellow oil48 (70%); 1H NMR (300 MHz, CDCl3): δ = 7.96 (dd, J = 8.4, 0.9 Hz, 1 H), 7.60 (dd, J = 8.7, 0.9 Hz, 1 H), 7.50–7.45 (m, 1 H), 7.36–7.30 (m, 1 H), 4.71–4.64 (m, 2 H), 4.56–4.49 (m, 1 H), 4.25 (br s, 1 H), 1.65–1.34 (m, 6 H), 0.92 (t, J = 7.5 Hz, 3 H). 13C NMR (75 MHz, CDCl3): δ = 145.5, 133.8, 128.5, 127.4, 124.0, 119.7, 109.9, 71.0, 54.0, 34.3, 27.6, 22.6, 14.0. HRMS: m/z calcd for C12H17N3ONa [M + Na]+: 242.1264; found: 242.1266
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