Synlett 2010(11): 1669-1673  
DOI: 10.1055/s-0030-1258082
LETTER
© Georg Thieme Verlag Stuttgart ˙ New York

A Facile Synthesis of Novel Pyrrolidine Dendrimers by Terminal Group Modification through 1,3-Dipolar Cycloaddition Reaction

Perumal Rajakumar*, Sebastian Raja, Ayyavu Thirunarayanan
Department of Organic Chemistry, University of Madras, Guindy Campus, Chennai 600 025, India
Fax: +91(44)22300488; e-Mail: perumalrajakumar@gmail.com;
Further Information

Publication History

Received 30 March 2010
Publication Date:
11 June 2010 (online)

Abstract

A series of novel dendrimers with pyrrolidine as surface group has been achieved in high yields by terminal-group modification on chalcone dendrimers through the application of 1,3-dipolar cycloaddition reaction. In 1,3-dipolar cycloaddition, azomethine ylides (AMY) with alkenes afforded five-membered N-methyl pyrrolidine. The formation of N-methyl pyrrolidine in the dendritic structure would be an important candidate in the field of biology and pharmacology.

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Dendrimer 1 Yield 91%; mp 126-128 ˚C. MS (MALDI-TOF): m/z = 1000 [M+]. ¹H NMR (300 MHz, CDCl3): δ = 2.39 (s, 9 H), 2.42 (s, 9 H), 2.78-2.92 (m, 6 H), 3.05-3.14 (m, 6 H), 3.88-3.99 (m, 6 H), 5.11 (s, 6 H), 6.95 (d, 6 H, J = 8.4 Hz), 7.20-7.33 (m, 15 H), 7.81 (d, 6 H, J = 8.1 Hz). ¹³C NMR (75 MHz, CDCl3): δ = 16.0, 42.1, 46.8, 55.2, 60.5, 64.3, 65.1, 114.1, 126.5, 127.7, 128.6, 129.8, 131.0, 131.3, 139.6, 144.4, 162.9, 198.1. Anal. Calcd for C66H69N3O6: C, 79.25; H, 6.95; N, 4.20. Found: C, 79.37; H, 6.81; N, 4.31.

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Dendrimer 2 Yield 85%; mp 144-146 ˚C. MS (MALDI-TOF): m/z = 2198 [M+]. ¹H NMR (300 MHz, CDCl3): δ = 2.39 (s, 9 H), 2.41 (s, 18 H), 2.78-2.93 (m, 12 H), 3.03-3.13 (m, 12 H), 3.83-3.97 (m, 12 H), 5.07 (s, 18 H), 6.91 (d, 12 H, J = 8.7 Hz), 6.97 (s, 3 H), 7.03-7.31 (m, 36 H), 7.77 (d, 12 H, J = 8.7 Hz). ¹³C NMR (75 MHz, CDCl3): δ = 14.1, 31.6, 42.0, 46.9, 55.1, 60.4, 64.3, 69.8, 113.2, 114.4, 116.6, 126.5, 127.6, 128.6, 129.9, 131.0, 138.3, 144.3, 162.4, 198.1. Anal. Calcd for C144H144N6O15: C, 78.66; H, 6.60; N, 3.82. Found: C, 78.57; H, 6.67; N, 3.73.

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Dendrimer 3 Yield 89%; mp 174-176 ˚C. MS (MALDI-TOF): m/z = 1838 [M+]. ¹H NMR (300 MHz, CDCl3): δ = 2.46 (s, 18 H), 2.95-3.24 (m, 24 H), 3.79-3.98 (m, 12 H), 5.06 (s, 12 H), 6.68 (s, 12 H), 7.08-7.19 (m, 30 H), 7.60 (s, 12 H). ¹³C NMR (75 MHz, CDCl3): δ = 31.6, 41.9, 46.9, 54.4, 59.9, 63.6, 114.1, 126.9, 127.6, 128.6, 128.8, 130.1, 131.1, 137.5, 161.9, 198.1. Anal. Calcd for C120H120N6O12: C, 78.40; H, 6.58; N, 4.57. Found: C, 78.53; H, 6.69; N, 4.45.

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Dendrimer 4 Yield 79%; mp 130-132 ˚C. MS (MALDI-TOF): m/z = 4235 [M+]. ¹H NMR (300 MHz, CDCl3): δ = 2.34 (s, 36 H), 2.73-2.84 (m, 24 H), 3.01 (s, 24 H), 3.76-3.88 (m, 24 H), 4.77 (s, 24 H), 5.14 (s, 12 H), 6.68 (d, 24 H, J = 7.5 Hz), 6.79 (s, 12 H), 6.88 (s, 6 H), 7.08-7.19 (m, 60 H), 7.61 (d, 24 H, J = 7.8 Hz). ¹³C NMR (75 MHz, CDCl3): δ = 30.6, 40.9, 45.8, 53.9, 59.3, 63.1, 68.5, 112.3, 113.3, 125.6, 126.1, 126.6, 127.0, 127.6, 128.8, 129.9, 137.4, 142.9, 157.8, 161.2, 196.8. Anal. Calcd for C276H270N12O30: C, 78.27; H, 6.43; N, 3.97. Found: C, 78.38; H, 6.53; N, 3.89.