Synlett 2017; 28(19): 2642-2646
DOI: 10.1055/s-0036-1588531
letter
© Georg Thieme Verlag Stuttgart · New York

β-Lactam-Synthon-Interceded Metal/Acid-Free Diastereoselective Access to Highly Functionalized Oxazol-5-ones and Dihydroimidazoles

Amandeep Singh
a   Department of Chemistry, Guru Nanak Dev University, Amritsar 143005, India   Email: vipan_org@yahoo.com
,
Shalini,
Harleen Kaur
a   Department of Chemistry, Guru Nanak Dev University, Amritsar 143005, India   Email: vipan_org@yahoo.com
,
Palak Sharma
a   Department of Chemistry, Guru Nanak Dev University, Amritsar 143005, India   Email: vipan_org@yahoo.com
,
Amit Anand
b   Department of Chemistry, Khalsa College, Amritsar 143005, India
,
Vipan Kumar*
a   Department of Chemistry, Guru Nanak Dev University, Amritsar 143005, India   Email: vipan_org@yahoo.com
› Author Affiliations
A.A. wishes to thank the University Grants Commission, New Delhi, India for financial support under grant no. ROMRP-NRCB-CHEM-2015-16-87198
Further Information

Publication History

Received: 22 May 2017

Accepted after revision: 11 July 2017

Publication Date:
11 August 2017 (online)


Abstract

Facile diastereoselective access to functionalized oxazol-5-ones and dihydroimidazoles was accomplished through base-promoted intramolecular amidolysis and methoxide-assisted tandem intramolecular amidolysis/ring opening/intramolecular cyclization, respectively, of C-3-functionalized azetidin-2-ones.

Supporting Information

 
  • References

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  • 29 Oxazol-5-ones (3af); General Procedure A solution of the appropriate azetidinone 2 (1.0 mmol) in anhyd DMF (5 mL) was added dropwise to a stirred suspension of t-BuOK (1.2 mmol) in anhyd DMF (5 mL), and the mixture was stirred at r.t. for 30 min. When the reaction was complete (TLC), the mixture was concentrated under reduced pressure and extracted with EtOAc (3 × 20 mL). The combined organic layers were dried (Na2SO4), filtered, and concentrated under vacuum to afford a crude product that was purified by column chromatography [silica gel, EtOAc–hexane (40:60)].
  • 30 2-Methyl-4-{(2E)-1-[(4-tolyl)amino]-3-phenylprop-2-en-1-yl}-1,3-oxazol-5(4H)-one (3b) Off-white solid; yield: 92 mg (80%); mp 160–162 °C. 1H NMR (400 MHz, CDCl3): δ = 2.03 (s, 3 H, CH3), 2.26 (s, 3 H, CH3), 4.53 (dd, J 1,2 = 1.76, J 1,3 = 7.88 Hz, 1 H, H-2), 4.78 (dd, J 1,2 = 2.12, J 1,3 = 7.32 Hz, 1 H, H-1), 6.28 (dd, J 1,2 = 7.92, J 1,3 = 15.96 Hz, 1 H, H-3), 6.73 (d, J = 15.9 Hz, 1 H, H-4), 7.04 (d, J = 8.2 Hz, 2 H, Ar-H), 7.24–7.36 (m, 7 H, Ar-H). 13C NMR (100 MHz, CDCl3): δ = 21.0, 22.9, 62.8, 63.3, 117.4, 124.9, 126.8, 128.4, 128.7, 129.7, 134.2, 134.7, 135.0, 135.6, 164.0, 170.7. HRMS: m/z [M+] calcd for C20H20N2O2: 320.1525; found. 320.1530. 4-{(2E)-1-[(4-Chlorophenyl)amino]-3-phenylprop-2-en-1-yl}-2-methyl-1,3-oxazol-5(4H)-one (3c) Off-white solid; yield: 90.3 mg (79%); mp 164–165 °C. 1H NMR (400 MHz, CDCl3): δ = 2.03 (s, 3 H, CH3), 4.62 (dd, J 1,2 = 2.00, J 1,3 = 8.08 Hz, 1 H, H-2), 4.73 (dd, J 1,2 = 2.3, J 1,3 = 7.32 Hz, 1 H, H-1), 6.28 (dd, J 1,2 = 8.04, J 1,3 = 15.92 Hz, 1 H, H-3), 6.76 (d, J = 15.92 Hz, 1 H, H-4), 7.21 (d, J = 8.8 Hz, 2 H, Ar-H), 7.26–7.37 (m, 7 H, Ar-H). 13C NMR (100 MHz, CDCl3): δ = 22.9, 62.7, 63.8, 118.6, 124.4, 126.8, 128.7, 128.8, 129.3, 129.7, 135.1, 136.0, 164.2, 170.7. HRMS: m/z [M+] calcd for C19H17ClN2O2: 340.0979; found: 340.0986. 4-{(2E)-1-[(4-Fluorophenyl)amino]-3-phenylprop-2-en-1-yl}-2-methyl-1,3-oxazol-5(4H)-one (3d) Off-white solid; yield: 94.2 mg (82%); mp 170–172 °C. 1H NMR (400 MHz, CDCl3): δ = 2.03 (s, 3 H, CH3), 4.62 (ddd, J 1,2 = 0.72, J 1,3 = 2.36, J 1,5 = 8.08 Hz, 1 H, H-2), 4.73 (dd, J 1,2 = 2.4, J 1,3 = 7.32 Hz, 1 H, H-1), 6.27 (dd, J 1,2 = 8.08, J 1,3 = 15.96 Hz, 1 H, H-3), 6.76 (d, J = 15.96 Hz, 1 H, H-4), 7.21 (d, J = 9.0 Hz, 2 H, Ar-H), 7.26–7.37 (m, 7 H, Ar-H). 13C NMR (100 MHz, CDCl3): δ = 22.9, 62.7, 63.7, 118.6, 124.4, 126.8, 128.7, 128.8, 129.3, 129.7, 135.1, 135.4, 136.0, 164.2, 170.8. HRMS: m/z [M+] calcd for C19H17FN2O2: 324.1274; found: 324.1261.
  • 31 Bifulco G. Dambruoso P. Gomez-Paloma L. Riccio R. Chem. Rev. 2007; 107: 3744
  • 32 4,5-Dihydro-1H-imidazoles 5af; General Procedure A solution of the appropriate azetidinone 2 in anhyd MeOH (10 mL) was added to a stirred solution of NaOMe (2.0 equiv) in anhyd MeOH (5 mL), and the mixture was stirred at 80 °C for 6 h until the reaction was complete (TLC). The mixture was then concentrated and extracted with EtOAc (3 × 20 mL). The combined organic layers were dried over anhyd Na2SO4, filtered, and concentrated under vacuum to obtain a crude product that was purified by column chromatography [silica gel, EtOAc–hexane (10:90)].
  • 33 Methyl 1-(4-Chlorophenyl)-2-methyl-5-[(E)-2-phenylvinyl]-4,5-dihydro-1H-imidazole-4-carboxylate (5c) Brown oil; yield: 84.5 mg (71%). 1H NMR (500 MHz, CDCl3): δ = 2.06 (s, 3 H, CH3), 3.76 (s, 3 H, OCH3), 4.48 (t, J = 4.90 Hz, 1 H, H-1), 4.95 (dd, J 1,2 = 4.95, J 1,3 = 7.30 Hz, 1 H, H-2), 6.07 (dd, J 1,2 = 6.35, J 1,3 = 15.86 Hz, 1 H, H-3), 6.62 (d, J = 15.7 Hz, 1 H, H-4), 6.67 (d, J = 8.55 Hz, 2 H, Ar-H), 7.14 (d, J = 8.60 Hz, 2 H, Ar-H), 7.32–7.35 (m, 5 H, Ar-H). 13C NMR (125 MHz, CDCl3): δ = 23.2, 52.7, 55.8, 58.2, 114.9, 122.9, 125.8, 126.6, 128.0, 128.6, 129.1, 133.1, 136.0, 145.0, 170.3, 170.7. HRMS: m/z [M + H]+ calcd for C20H19ClN2O2: 355.1135; found: 355.1153.