Download PDF
Synlett 2004(14): 2627-2629  
DOI: 10.1055/s-2004-834834
LETTER
© Georg Thieme Verlag Stuttgart · New York

Hexacarboxylic Acid Biscavitands

Gang Zhao, Peter P. Castro, Linda M. Gutierrez-Tunstad*
Department of Chemistry and Biochemistry, California State University, 5151 State University Drive, Los Angeles, CA 90032, USA
Fax: +1(323)3436490; e-Mail: ltunsta@calstatela.edu;
Further Information

Publication History

Received 5 August 2004
Publication Date:
20 October 2004 (online)

    Permissions and Reprints All articles of this category

Abstract

The synthesis of hexacarboxylic acid biscavitands is described. These new singly bridged biscavitands are based on resorcin[4]arene with a flexible all-carbon bridge at one 2-resorcyl position and carboxylic acids at the remaining 2-resorcyl positions. Preliminary self-assembling behavior of these new biscavitands is described.

Key words

cavitand - biscavitand - self-assembly - lithiation

7

General Procedure for Making Biscavitands 2a-c: To a stirred solution of cavitand 1 (0.5 mmol) in freshly dried THF (20 mL) at -78 °C under Ar, n-BuLi in hexanes (1.6 M, 1.10 equiv) was added via syringe. After 15 min at -78 °C, the dry ice-acetone bath was removed. Stirring was continued for 15 min, then at -78 °C, the diiodoalkane (0.48 equiv) was added. The reaction mixture was slowly warmed to ambient temperature with stirring over 2 h. The solvent was then removed in vacuo. Brine (20 mL) and 10% HCl (10 mL) were added to the residue, which was then extracted with Et2O (50 mL). The ether extract was dried over MgSO4, evaporated in vacuo, and the crude was separated by flash chromatography on silica gel, yielding the desired biscavitands.

8

Biscavitand 2a: 35% yield; mp 166 °C (dec.). 1H NMR (300 MHz, CDCl3): δ = 7.09 (s, 6 H, bottom Ar-H), 6.95 (s, 2 H, bottom Ar-H), 6.46 (s, 6 H, top Ar-H), 5,74 (d, J = 4.8 Hz, 4 H, outer of -CHH-), 5.72 (d, J = 5.1 Hz, 4 H, outer of -CHH-), 4.69 (m, 8 H, Ar2 CH-, two overlapping triplets), 4.39 (d, J = 7.2 Hz, 4 H, inner of -CHH-), 4.30 (d, J = 7.2 Hz, 4 H, inner of -CHH-), 2.27 (m, 4 H, -CH 2CH2CH2-
CH 2-), 2.19 [m, 16 H, -CH 2 (CH2)3CH3], 1.34 [m, 52 H,
-CH2(CH 2 ) 3 CH3 and -CH2 CH 2 CH 2 CH2-], 0.89 [t, J = 6.0 Hz, 24 H, -CH2 (CH2)3 CH 3 ]. 13C NMR (75 MHz, CDCl3): δ = 155.1, 154.9, 153.4, 138.6, 138.4, 138.1, 128.4, 120.9, 120.8, 117.8, 116.6, 116.4, 99.7, 99.5, 36.9, 36.5, 32.2, 30.2, 30.0, 27.8, 27.7, 25.6, 22.9, 14.3. HRMS-MALDI: m/z calcd for C108H134O16Na [M + Na]+: 1709.9564 (error 1.9 ppm). Found: 1709.9596.

9

Biscavitand 2b: 32% yield; mp 157 °C (dec.). 1H NMR (300 MHz, CDCl3): δ = 7.09 (s, 6 H, bottom Ar-H), 6.95 (s, 2 H, bottom Ar-H), 6.45 (s, 6 H, top Ar-H), 5.78 (d, J = 7.2 Hz, 4 H, outer of -CHH-), 5.72 (d, J = 7.2 Hz, 4 H, outer of
-CHH-), 4.70 (t, J = 7.8 Hz, 8 H, Ar2 CH-), 4.39 (d, J = 7.2 Hz, 4 H, inner of -CHH-), 4.32 (d, J = 7.2 Hz, 4 H, inner of -CHH-), 2.27 [m, 4 H, -CH 2 (CH2)3 CH 2 -], 2.21 [m, 16 H, -CH 2 (CH2)3CH3], 1.36 [m, 54 H, -CH2 (CH 2 ) 3 CH3 and
-CH2 (CH 2 ) 3 CH2-], 0.88 [t, J = 6.0 Hz, 24 H,
-CH2(CH2)3 CH 3 ]. 13C NMR (75 MHz, CDCl3): δ = 155.1, 154.9, 153.4, 138.6, 138.4, 138.1, 128.6, 120.9, 120.8, 117.8, 116.6, 116.5, 99.7, 99.5, 36.9, 36.5, 32.2, 30.2, 30.0, 29.8, 27.7, 25.6, 22.9, 14.3; HRMS-MALDI: m/z calcd for C109H136O16Na [M + Na]+: 1723.9726 (error -0.4 ppm). Found: 1723.9713.

10

Biscavitand 2c: 30% yield; mp 150 °C (dec.). 1H NMR (300 MHz, CDCl3): δ = 7.11 (s, 6 H, bottom Ar-H), 6.96 (s, 2 H, bottom Ar-H), 6.47 (s, 6 H, top Ar-H), 5.79 (d, J = 7.2 Hz, 4 H, outer of -CHH-), 5.73 (d, J = 7.2 Hz, 4 H, outer of
-CHH-), 4.72 (t, J = 7.8 Hz, 8 H, Ar2 CH-), 4.41 (d, J = 7.2 Hz, 4 H, inner of -CHH-), 4.34 (d, J = 7.2 Hz, 4 H, inner of -CHH-), 2.26 [m, 4 H, -CH 2 (CH2)4CH 2 -], 2.23 [m, 16 H, -CH 2 (CH2)3CH3], 1.35 [m, 56 H, -CH2 (CH 2 ) 3 CH3 and
-CH2 (CH 2 ) 4 CH2-], 0.89 [t, J = 6.0 Hz, 24 H,
-CH2(CH2)3 CH 3 ]. 13C NMR (75 MHz, CDCl3): δ = 155.1, 154.9, 153.3, 138.6, 138.4, 138.1, 128.7, 120.9, 120.8, 117.7, 116.5, 116.4, 99.7, 99.5, 36.9, 36.5, 32.2, 30.1, 30.0, 29.7, 27.7, 25.6, 22.9, 14.2. HRMS-MALDI: m/z calcd for C110H138O16Na [M + Na]+: 1737.9877 (error 0.69 ppm). Found: 1737.9889.

11

General Procedure for Making Hexacarboxylic Acid Biscavitands 3a-c: To a stirred solution of biscavitand 2 (0.2 mmol) in freshly dried THF (15 mL) at -78 °C under Ar, n-BuLi (1.6 M in hexanes, 6.6 equiv) was added in one portion via syringe. The resulting mixture was stirred at
-78 °C for 10 min, the cooling bath was removed and stirring was continued for an additional 10 min. The ice bath was replaced and ‘bone dry’ grade CO2 (Gilmore Liquid Air Company, South El Monte, CA 91733) was bubbled into the reaction mixture for 15 min (white solids formed immediately). The reaction was quenched with 1.0 N HCl (2.0 mL). THF was evaporated in vacuo. The white solids were collected by filtration and washed thoroughly with H2O, then dried in vacuo. This material was used in the self-assembly studies. Further purification by recrystallization from CH2Cl2-acetone was carried out. The recovery yields, however, were less than 40%. No signal for lower homologs was detected after recrystallization.

12

Biscavitand 3a: 97% yield; mp 215 °C (dec.). 1H NMR (300 MHz, acetone-d 6): δ = 7.73 (s, 2 H, bottom Ar-H), 7.68 (s, 4 H, bottom Ar-H), 7.47 (s, 2 H, bottom Ar-H), 5.82 (d, J = 7.5 Hz, 4 H, outer of -CHH-), 5.74 (d, J = 7.5 Hz, 4 H, outer of -CHH-), 4.76 (t, J = 7.2 Hz, 8 H, Ar2 CH-), 4.50 (d, J = 7.5 Hz, 4 H, inner of -CHH-), 4.42 (d, J = 7.5 Hz, 4 H, inner of -CHH-), 2.41 [m, 20 H, -CH 2CH2CH2CH 2- and
-CH 2 (CH2)3CH3], 1.33 [52 H, m, -CH2 (CH 2 ) 3 CH3 and
-CH2 CH 2 CH 2 CH2-], 0.89 [m, 24 H, -CH2(CH2)3 CH 3 ]. 13C NMR (75 MHz, acetone-d 6): δ = 166.3, 154.3, 152.1, 151.6, 151.3, 140.0, 139.7, 138.9, 138.5, 130.7, 125.6, 125.5, 123.6, 123.4, 119.5, 100.6, 100.1, 39.8, 37.9, 37.5, 32.7, 32.6, 30.8, 30.5, 28.5, 26.4, 23.9, 23.4, 14.4. HRMS-MALDI: m/z calcd for C114H134O28Na [M + Na]+: 1973.8954 (error -5.5 ppm). Found: 1973.8845.

13

Biscavitand 3b: 95% yield; mp 206 °C (dec.). 1H NMR (300 MHz, acetone-d 6): δ = 7.72 (s, 2 H, bottom Ar-H), 7.67 (s, 4 H, bottom Ar-H), 7.46 (s, 2 H, bottom Ar-H), 5.79 (d, J = 7.5 Hz, 4 H, outer of -CHH-), 5.72 (d, J = 7.5 Hz, 4 H, outer of -CHH-), 4.76 (t, J = 7.2 Hz, 8 H, Ar2 CH-), 4.50 (d, J = 7.5 Hz, 4 H, inner of -CHH-), 4.43 (d, J = 7.5 Hz, 4 H, inner of -CHH-), 2.40 [m, 20 H, -CH 2 (CH2)3 CH 2 - and
-CH 2 (CH2)3CH3], 1.38 [m, 54 H, -CH2 (CH 2 ) 3 CH3 and
-CH2 (CH 2 ) 3 CH2-], 0.91 [m, 24 H, -CH2(CH2)3 CH 3 ]. 13C NMR (75 MHz, acetone-d 6): δ = 166.4, 154.3, 152.0, 151.7, 151.4, 140.0, 139.7, 138.9, 138.5, 130.6, 125.8, 125.7, 123.5, 123.4, 119.5, 100.6, 100.2, 40.5, 39.8, 37.9, 37.5, 32.7, 32.6, 30.5, 28.4, 26.4, 24.1, 23.4, 14.4. HRMS-MALDI: m/z calcd for C115H137O2 [M + H]+: 1965.9291 (error -2.9 ppm). Found: 1965.9234.

14

Biscavitand 3c: 97% yield; mp 198 °C (dec.). 1H NMR (300 MHz, acetone-d 6): δ = 7.72 (s, 2 H, bottom Ar-H), 7.68 (s, 4 H, bottom Ar-H), 7.46 (s, 2 H, bottom Ar-H), 5.78 (d, J = 7.5 Hz, 4 H, outer of -CHH-), 5.72 (d, J = 7.5 Hz, 4 H, outer of -CHH-), 4.76 (t, J = 7.2 Hz, 8 H, Ar2 CH-), 4.50 (d, J = 7.5 Hz, 4 H, inner of -CHH-), 4.42 (d, J = 7.5 Hz, 4 H, inner of -CHH-), 2.38 [m, 20 H, -CH 2 (CH2)4 CH 2 - and
-CH 2 (CH2)3CH3], 1.37 [m, 56 H, -CH2 (CH 2 ) 3 CH3 and
-CH2 (CH 2 ) 4 CH2-], 0.91 [m, 24 H, -CH2(CH2)3 CH 3 ]. 13C NMR (75 MHz, acetone-d 6): δ = 166.3, 154.2, 152.1, 151.6, 151.4, 140.0, 139.7, 138.9, 138.5, 130.7, 125.7, 125.5, 123.6, 123.5, 119.5, 100.6, 100.1, 39.8, 37.8, 37.5, 32.7, 32.6, 30.4, 28.4, 26.4, 24.1, 23.3, 14.3. HRMS-MALDI: m/z calcd for C116H138O28Na [M + Na]+: 2001.9272 (error
-1.2 ppm). Found: 2001.9242.