α-Regioselective Barbier Reaction of Carbonyl Compounds and Allyl Halides Mediated by Praseodymium

Abstract

The first utility of praseodymium as a mediating metal in the Barbier reaction of carbonyl compounds with allyl halides was reported in this paper. In contrast to the traditional metal-mediated or catalyzed Barbier reactions, exclusive α-adducts were obtained in this one-pot reaction with a broad scope of substrates and feasible reaction conditions.

Neodymium-Promoted Highly Selective Carbon–Carbon Double Bond Formation of Ketones with Allyl Halides in the Presence of Diethyl Phosphite

“…Data are reported as follows: chemical shift, multiplicity (standard abbreviations), coupling constants (Hz), and integration. 13 C NMR spectra were recorded at 100 MHz. Chemical shifts are reported in parts per million relative to the central line of the multiplet at 77.5 ppm for CDCl 3 .…”

“…1 H NMR (CDCl 3 /TMS, 400 MHz):  = 7.38-7.19 (m, 10 H), 6.71 (d, J = 8.0 Hz, 1 H), 6.47-6.43 (m, 1 H), 5.40-5.36 (m, 1 H), 5.13-5.10 (m, 1 H). 13 C NMR (CDCl 3 /TMS, 101 MHz,):  = 143. 10, 142.04, 139.61, 134.92, 130.37, 128.48, 128.15, 128.12, 127.54, 127.46, 127.35, 118.57 1,1-Bis(4-methoxyphenyl)buta-1,3-diene (2ba) Colorless oil; yield: 100 mg (77%, from allyl bromide), 118.3 mg (91%, from allyl iodide).…”

“…1 H NMR (CDCl 3 /TMS, 400 MHz):  = 7.13-7.09 (m, 2 H), 7.05-7.02 (m, 2 H), 6.82-6.78 (m, 2 H), 6.73-6.69 (m, 2 H), 6.50 (d, J = 12.0 Hz, 1 H), 6.41-6.31 (m, 1 H), 5.23 (dd, J = 16.0, 4.0 Hz, 1 H), 4.96 (dd, J = 12.0, 4.0 Hz, 1 H), 3.72 (s, 3 H), 3.67 (s, 3 H). 13 C NMR (CDCl 3 /TMS, 101 MHz):  = 158. 85, 142.34, 136.70, 135.21, 131.55, 128.79, 126.64, 117.21, 52.28.…”

“…1 H NMR (CDCl 3 /TMS, 400 MHz):  = 7.38-7.34 (m, 2 H), 7.32-7.28 (m, 1 H), 7.27-7.24 (m, 4 H), 7.23-7.19 (m, 3 H), 6.87 (d, J = 11.4 Hz, 1 H), 5.93 (dp, J = 11.3, 1.4 Hz, 1 H), 1.88 (s, 3 H), 1.75 (s, 3 H). 13 C NMR (CDCl 3 /TMS, 101 MHz):  = 143. 08, 140.17, 139.69, 137.65, 130.55, 128.09, 128.07, 127.40, 126.98, 126.87, 124.47, 123.17, 26.47, 18.60.…”

“…6 Zerovalent lanthanoid metals have strong reduction potential 7 and these metals show great advantages not only as nontoxic, cheap and stable in the air, but also electrontransfer-efficiency as reductant. That is why more and more lanthanoid metals such as Sm, 8 Dy, 9 Ce, 10 Yb, 11 La, 12 and Pr 13 have been employed as useful reagents or catalysts in organic synthesis. However, the application of reduction of zerovalent neodymium metal has been ignored for over one decade until the first report from our group appeared.…”