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Synlett 2010(9): 1394-1396  
DOI: 10.1055/s-0029-1219833
LETTER
© Georg Thieme Verlag Stuttgart ˙ New York

Synthesis of New Chiral Smectic Mesogenes with 4-(2-Phenylethyl)biphenyl and 4-[2-(3-Fluorophenyl)ethyl]biphenyl Molecular Cores

Przemysław Kula*, Anna Spadło, Magdalena Żurowska, Roman Dąbrowski
Institute of Chemistry, Department of New Technologies and Chemistry, Military University of Technology, Kaliskiego 2, 00-908 Warsaw, Poland
Fax: +48(22)6839582; e-Mail: pkula@wat.edu.pl;
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Publication History

Received 19 January 2010
Publication Date:
15 April 2010 (online)

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Abstract

Two methods of synthesis of chosen 1-[4-(1-methyl-heptyloxycarbonyl)phenyl]-2-[4′-(2,2,3,3,4,4,4-heptafluorobutoxy­alkoxy)biphenyl-4-yl]ethanes and 1-[3-fluoro-4-(1-methylheptyloxy­carbonyl)phenyl]-2-[4′-(2,2,3,3,4,4,4-heptafluorobutoxyalkoxy)bi-phenyl-4-yl]ethanes have been proposed, checked and compared. The compounds were prepared by Sonogashira coupling of 4-benzyl­oxy-4′-ethynylbiphenyl with appropriate 4-halobenzoate esters followed by parallel hydrogenation of ethynylene bridge and debenzylation of hydroxyl group. The 1-[4-(1-methylheptyloxycarbonyl)phenyl]-2-[4′-hydroxybiphenyl-4-yl]ethane and 1-[3-fluoro-4-(methoxycarbonyl)phenyl]-2-[4′-hydroxybiphenyl-4-yl]ethane thus obtained has been transformed into final products by Mitsunobu reaction with ω-(2,2,3,3,4,4,4-heptafluorobutoxy)alkan-1-ols, followed by the replacing of an ester terminal chain in the case of second method.

Key words

coupling - Mitsunobu reaction - alkynes - biaryls - self-assembly

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Synthesis of 4-Benzyloxy-4′-ethynylbiphenyl (3)
4-Benzyloxy-4-bromobiphenyl (128.8 g, 0.38 mol), Et3N (57.6 g, 0.57 mol), DBU (29 g, 0.19 mol), PdCl2 (PPh3)2 (2 g, 2.85 mmol), CuI (1 g, 5.27 mmol), and THF (400 mL) have been added in a 1 L nitrogen-filled flask. The mixture were heated(boiling) for 5 min, and 2-methyl-3-butyn-2-ol (38.3 g, 0.456 mol) has been dropped in slowly. After 4 h of stirring the GC-MS analysis was performed. To complete the reaction, 25% of the initial amount of 2-methyl-3-butyn-2-ol and 0.5g of PdCl2 (PPh3)2 were added and stirred for additional 8 h. Then the reaction mixture was poured onto H2O and the solid was filtered off, dried and washed using CH2Cl2 (0.5 L). The obtained 4-[4′-(benzyloxy)biphenyl-4-yl]-2-methylbut-3-yn-2-ol (112 g, 0.33 mol), NaH (1.1 g, 46 mmol) and dry toluene (1 L) have been placed in a flask equipped with column and distillation head to distill off the emerging acetone. When the distillate temperature reached the bp of toluene, the reaction mixture was cooled down and poured onto the H2O. The organic layer was separated and poured through active carbon pad and dried over anhyd MgSO4. The toluene solution was concentrated and the final product crystallized in freezer. 4-Benzyloxy-4′-ethynyl-biphenyl (3) was obtained in 57% yield (61.5 g, 0.217 mol).
MS (EI 70eV): m/z = 284 [M+ ], 193, 165, 139, 91, 65. IR (neat): 3282, 3061, 3036, 2861, 2359, 2340, 1600, 1488, 1454, 1380, 1284, 1246, 1026, 1008, 812, 738, 619. ¹H NMR (200 MHz, CDCl3): δ = 7.53 (m, 2 H, ArH), 7.51 (m, 5 H, ArH), 7.43 (m, 2 H, ArH), 7.39 (m, 2 H, ArH), 7.03 (m, 2 H, ArH), 5.10 (s, CH2), 3.11 (s, 1 H CºCH). ¹³C NMR (50 MHz, CDCl3): δ = 158.89 (1 C), 141.31 (1 C), 137.04 (1 C), 133.15 (1 C), 132.74 (2 CH), 128.84 (2 CH), 128.32 (2 CH), 128.25 (2 CH), 127.69 (1 CH), 126.70 (2 CH), 120.49 (1 C), 115.44 (2 CH), 83.87 (1 C), 77.87 (1 CH), 70.28 (1 CH2). Mp 156.7-157.2 ˚C (dec.).

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1-[( S )-4-(1-Methylheptyloxycarbonyl)phenyl]-2-[4′-(2,2,3,3,4,4,4-heptafluorobutoxyhexyloxy)biphenyl-4-yl]ethane (6.6) MS (EI 70eV): 712 [M+ ], 465, 183, 55. MS (ESI+, MeOH-H2O): 735 [M + Na+], 615. IR (neat): 2934, 2856, 1710, 1608, 1499, 1354, 1222, 1103, 810, 736 cm-¹. ¹³C NMR (50 MHz, CDCl3): δ = 166.29 (1 COO), 158.55 (1 CO), 146.94 (1 CEt), 139.63 (1 CEt), 138.69 (1 C), 133.38 (1 C), 129.67 (2 CH), 128.83 (2 CH), 128.75 (1 CCOO), 128.48 (2 CH), 127.95 (2 CH), 126.67 (2 CH), 114.74 (2 CH), 73.13 (1 COOC), 71.59 (1 CH2O), 67.88 (1 CH2O), 37.87 (1 CH2Ar), 37.12 (1 CH2Ar), 36.11 (1 CH2), 31.77 (1 CH2), 29.41 (1 CH2), 29.19 (2 CH2), 25.82 (1 CH2), 25.60 (1 CH2), 25.43 (1 CH2), 22.61 (1 CH2), 20.11 (CH3), 14.08 (CH3).

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1-[( S )-3-Fluoro-4-(1-methylheptyloxycarbonyl)phenyl]-2-[4′-(2,2,3,3,4,4,4-heptafluorobutoxybutoxy)biphenyl-4-yl]ethane (12.4) MS (EI, 70eV): m/z = 702 [M+ ], 465, 183, 55. MS (ESI+, MeOH-H2O): m/z = 725 [M + Na+], 605. IR (neat): 2950, 2859, 1699, 1622, 1499, 1354, 1219, 1117, 971, 817, 734.