Synthesis of Pinacol Allylic Boronic Esters via Olefin Cross-Metathesis between Pinacol Allylboronate and Terminal or Internal Alkenes

Abstract

The ruthenium-catalyzed olefin cross-metathesis between pinacol allylboronate, CH₂=CHCH₂B(O₂C₂Me₄), and RCH=CH₂ giving RCH=CHCH₂B(O₂C₂Me₄) was carried out in refluxing CH₂Cl₂ in the presence of an alkylidene-ruthenium complex (3 mol%).

Key words

allylboron - olefin cross-metathesis - ruthenium catalyst

References

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10

16c: HPLC on Chiralcel OB-H (Dicel Co., Ltd) with hexane-2-propanol (99.5:0.5) showed 82% ee; [α]_D ²⁵ = +37.5 (c 1.02, CHCl₃); ¹H NMR (400 MHz, CDCl₃) δ 5.73 (ddd, 1 H, J = 17.1, 10.2 and 8.3 Hz), 5.11-5.29 (m, 4 H), 3.24 (dddd, 1 H, J = 7.6 Hz), 2.69 (dd, 1 H, J = 17.3 and 8.0 Hz), 2.50 (dd, 1 H, J = 17.3 and 7.6 Hz), 1.78 (s, 1 H), 1.71 (s, 1 H). Two percent of NOE was observed between two hydrogens at the carbon atoms attached to ethenyl and 2-methyl-1-propenyl group; ¹³C NMR (100 MHz, CDCl₃) δ 18.4, 25.8, 34.3, 43.7, 79.7, 117.7, 118.7, 134.3, 140.3, 176.2; exact mass calcd for C₁₀H₁₄O₂ 166.0994, found 166.0992.