- S1 - Facile Synthesis of Highly Congested 1,2-Diphosphinobenzenes from Bis(phosphine)boronium Salts Supporting Information Yoshikazu Yamamoto, † Toru Koizumi, †,‡ Kosuke Katagiri, †,‡ Yui Furuya, † Hiroshi Danjo,* ,† Tsuneo Imamoto, ‡ and Kentaro Yamaguchi* ,† Department of Pharmaceutical Technology, Faculty of Pharmaceutical Sciences at Kagawa Campus, Tokushima Bunri University, and CREST, Japan Science and Technology Agency (JST), Shido, Sanuki, Kagawa 769-2193, Japan Department of Chemistry, Faculty of Science, Chiba University, Yayoi-cho, Inage-ku, Chiba 263-8522, Japan General. All manipulations were carried out under nitrogen atmosphere. NMR spectra were recorded on a JEOL JNM-ECX (400 MHz for 1 H, 162 MHz for 31 P, and 100 MHz for 13 C). Chemical shifts were reported in δ ppm referenced to an internal tetramethylsilane standard for 1 H NMR, and to an external 85% H 3 PO 4 standard for 31 P NMR. Residual chloroform (δ 77.0 for 13 C) was used as internal reference for 13 C NMR. 1 H, 13 C, and 31 P NMR spectra were recorded in CDCl 3 at 25 °C unless otherwise noted. IR spectra were recorded on a JASCO FT/IR-6300. Optical rotations were recorded on a JASCO P-1030 polarimeter with a sodium lamp. MS (ESI) spectra were recorded on JEOL JMS-T100LC spectrometers. HPLC analyses were performed on a Hitachi L-2130 pump, and L-2450 Diode Array detector with a chiral column. X-ray crystal structure data were collected using a Bruker SMART APEX II diffractmeter with Mo-Kα radiation. Materials. All reagents were obtained from commercial sources and used without further purification. All solvents were freshly distilled. Compound 2 and (R)-5 were prepared according to the literature procedure. 1 Bis(di-tert-butylphosphine)boronium bromide (3a·Br) Di-tert-butylchlorophosphine (1.08 mL, 6.0 mmol) was slowly added to a stirred suspension of lithium aluminum hydride (229 mg, 6.0 mmol) in Et 2 O (5.0 mL) at 0 °C, and the mixture was stirred at room temperature for 1 h. The reaction mixture was passed through a column of basic alumina gel with ca. 15 mL of Et 2 O elution. The volatiles were removed in vacuo, and the residue was dissolved in CH 2 Cl 2 (10 mL). To the solution was added monobromoborane−methylsulfide complex (2.7 mL of 1.0 M CH 2 Cl 2 solution, 2.7 mmol) at room temperature, and the mixture was stirred at intact temperature. After 40 h, the volatiles were removed in vacuo, and the residue was purified by column chromatography on silica gel with CHCl 3 /MeOH (20/1 to 10/1) to give 3a·Br as a white solid (743 mg, 72%). 1 H NMR (400 MHz, CDCl 3 ) δ 5.99 (d, J = 410 Hz, 2H), 1.7-0.6 (m, 2H), 1.49 (d, J = 15 Hz, 36H); 13 C NMR (100 MHz, CDCl 3 ) δ 32.9 (m), 28.8; 31 P NMR (162 MHz, CDCl 3 ) δ 55.8 (d, J = 95 Hz); IR (KBr) 2990, 2966, 2433, 2404, 2302, 1474, 820 cm -1 ; MS (ESI) m/z 305 (M–Br); Anal. Calcd. for: C, 49.89; H, 10.47. Found: C, 49.97; H, 10.51. ––––––––––––––––––––– 1 Katagiri, K.; Danjo, H.; Yamaguchi, K.; Imamoto, T. Tetrahedron 2005, 61, 4701-4707