- Magnesium turnings (1.61g,
0.066gatoms) in dry THF (100mL) under nitrogen was treated with a
little of 2-bromothiophene (10.0g, 0.06mol) in THF (50mL). Warming
initiated the reaction and the remainder added over 45 in. After
3.5h and a further 15 min. reflux, the cooled solution (0-5 C) was
transferred dropwise by canula to a mixture of 2,6-dibromopyridine
13.08g, 0.055mol), PdCl2.dppe (0.5g) and dry THF (50mL) under
nitrogen at -5 C. After 10h at 30 C ether was added (100mL), the
solution washed with 4M HCl solution (sat., 150mL), then water. The
dried and evaporated solution yielded an oil which was distilled (b.p.
150 C/0.1mm) to give 2-bromo-6-(2-thienyl)pyridine as a colourless
- Thiophene (20.0g, 0.24mol) in dry THF (150mL)
at -40 C under nitrogen was treated with n-butyllithium (0.24mol),
stirred for 30 min. and then at -10 C for 30 min. This solution was
cooled to -50 C and trimethyl borate 88g, 0.85mol) added over 1h.
After a further 30 min. at -50 C the solution was warmed to ambient,
neutralised with 2M HCl ether extracted, and the ether layer extracted
3 times with 3M NaOH. The aqueous layer was acidfied at 0-10 C and
then extracted with ether (3x) and evaporated to give waxy white
solid (37.4g, 79%) used without further purification.
mixture of 2,6-dibromopyridine (1.00g, 4.22 mmol),
tetrakis-(triphenyl- phosphine)palladium (0.175g), toluene (30mL),
water 30mL), KF (1.0g) and thiophenboronic acid (2.5g) were refluxed
under nitrogen for 4h. The toluene layer was washed with water,
dried, evaporated and flash chromatographed (SiO2, PE/EtOAc 7:3) to
give ,6-bis-(2-thienyl)pyridine (TPT for short) (0.91g, 90%), m.p.
- To Mg (0.30g, 0.012gatoms)in dry THF (20mL) under
nitrogen was added dropwise 1,2-dibromoethane (1.85g, 9.85mmol) in THF
(30mL) and the solution refluxed for 50 min. In a separate flask,
n-butyllithium (9.02mmol) was added to TPT (1.00g., 4.0mmol) in dry
THF (20mL) at -40 C under nitrogen and after a further 30 min. at -40
C warmed to 0 C for 30 min., cooled to -60 C and the above MgBr2
solution added. After 30 min. at -60 C the solution was warmed to
ambient to give the bis-Grignard reagent used directly as below.
To the above solution was added a solution of
2-bromo-6-(2-thienyl)pyridine (2.41g, 0.01mol) and PdCl2.dppb) in dry
THF 20mL) and the mixture refluxed for 4h. Removal of the THF and
addition of CHCl3 gave a solution that was washed with sat. NH4Cl then
water, dried and evaporated to give a yellow solid that was flash
chromatographed (SiO2, PE/CH2Cl2 6:4) to give TPTPTPT (1.24g, 57%) as
yellow crystals from ethyl acetate, m.p.117.5-8.5 C.
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