Bifurans via palladium-catalyzed Suzuki coupling

Article abstract of DOI:10.3987/COM-15-13318

Sixteen 2,2'-bifurans with aryl substituents are reported. The copper-mediated oxidative coupling of lithium salt of furan led to the formation of 2,2'-bifuran, which was brominated with either 2 eq. or 4 eq. NBS to afford 5,5'-dibromo-2,2'-bifuran and 3,3',5,5'-tetrabromo-2,2'-bifuran. The palladiumcatalyzed Suzuki reactions between dibromo or tetrabormo-bifuran and arylboronic acid were employed to furnish the title compounds, which were characterized by NMR spectra and mass spectra.

Full text of DOI:10.3987/COM-15-13318

Supplmentary Materials for Heterocycles manuscript entitiled:
BIFURANS VIA PALLADIUM-CATALYZED SUZUKI COUPLING
Jun Zhang, Peijun Ye, Lu, He, Ting Yuan, and Qiancai Liu*
School of Chemistry and Molecular Engineering, East China Normal University, Shanghai 200241, China
Preparation of 1-3 S1-S2
A Schlenk flask was charged with furan (2 mL, 0.028 mol) and THF (30 mL) (freshly distilled
over Na and benzophenone diketal). After it was cooled to -78 C, a solution of n-BuLi (17.3
mL, 1.6 M, 0.028 mmol) was added dropwise. After addition, the mixture was warmed slowly
to room temperature and then heated at 50 C for 3h. Again the mixture was cooled to -78 C
and anhydrous CuCl (4.76 g, 0.028 mol) was added portion-wise, then it was warmed to room
temperature and stirred overnight before diluted aq. HCl (10%, 20 mL) was added to quench
the reaction at 0-5v C, and it was subsequently extracted with CH2Cl2 (3 x 100 mL). The
organic phase was washed twice with water and the solvent was carefully removed to
obtained crude 2,2’-bifuran, which was purified by column separation (Petro-ether, PE) to
afford a yellow liquid (0.85 g, 45%). Rf 0.80 (PE). 1H NMR δ: 7.43 (d, J = 1.6 Hz, 2H), 6.58
(d, J = 3.3 Hz, 2H), 6.47 (dd, J = 3.3, 1.8 Hz, 2H).
5,5’-dibromo-2,2’-bifuran (2) and 3,3’,5,5’-tetrabromo-2,2’-bifuran (3) S2
A three-necked round flask was charged with 2,2’-bifuran (0.85 g, 6.34 mmol) and benzene
(30 mL), then NBS (2.25 g, 12.68 mmol for 2; 4.5 g, 25.36 mmol for 3) was added with
exclusion of light. The stirring was continued for 5h before the solvents were evaporated. The
residue was dissolved in CH2Cl2 and washed with water (3 x 50 mL). After column separation
with petro-ether (PE), a white solid of 2 was obtained (1.3 g，72%), mp 75.1- 76.4C. Rf 0.56
(PE). 1H NMR δ: 6.51 (d, J = 3.4 Hz, 2H), 6.36 (d, J = 3.4 Hz, 2H). This materials has to be
used immediately before it became dark; 3,3’,5,5’-tetrabromo-2,2’- bifuran (3), white solid
(1.8 g, 64%), mp 111-112 C. Rf 0.66 (PE) 1H NMR δ: 6.48 (s, 2H).
S1 T. Kauffmann, H. Lexy, Chem. Ber. 1981,114, 3667;
S2 H. Ishida, K. Yui, Y. Aso, T. Otsubo, F. Ogura, Bull. Chem. Soc. Jpn. 1990, 63, 2828.

Fig.1 1H NMR, 13 NMR and HR-MS(ESI) for 4a

Fig.2 1H NMR, 13 NMR and HR-MS(ESI) for 4b

Fig.3 1H NMR, 13 NMR and HR-MS(ESI) for 4c

Fig.4 1H NMR, 13 NMR and HR-MS(ESI) for 4d

Fig.5 1H NMR, 13 NMR and HR-MS(ESI) for 4e

Fig.6 1H NMR, 13 NMR and HR-MS(ESI) for 4f

Fig.7 1H NMR, 13 NMR and HR-MS(ESI) for 4g

Fig.8 1H NMR, 13 NMR and HR-MS(ESI) for 4h

Fig. 9 1H NMR, 13 NMR and HR-MS(ESI) for 5a

Fig. 10 1H NMR, 13 NMR and HR-MS(ESI) for 5b

Fig. 11 1H NMR, 13 NMR and HR-MS(ESI) for 5c

Fig. 12 1H NMR and 13 NMR for 5d

Fig. 13 1H NMR and 13 NMR for 5e

Fig. 14 1H NMR, 13 NMR and HR-MS(ESI) for 5f

Fig. 15 1H NMR, 13 NMR and HR-MS(ESI) for 5g
Fig. 16 1H NMR and 13 NMR for 5h