Metal-catalysed multiple boration of ketimines†

Abstract

Metal-catalysed addition of B₂cat′₂ (cat′ = 4-Bu^t-1,2-O₂C₆H₃) to ketimines affords N-borylenamines and HBcat′. Analogous catalysed reactions of ketimines with HBcat′ in tetrahydrofuran afford multiply borated products, providing the first examples of metal-catalysed hydroboration of enamines.

References

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10. NMR data in [²H₈]THF: 2a: ¹H, δ7.6–6.8 (ov m, Ph + cat′, 13H), 5.73, 5.42 (s, =CH₂), 1.30 (9H, Bu^t); ¹³C, δ 148.3 (C=CH₂), 149.4, 147.2, 146.4, 144.8, 138.4 (ipso of CPh, NPh, and cat′), 129.4, 129.0, 127.5, 123.4 (o-, m-C of NPh and CPh), 128.9, 124.1 (p-C of NPh and CPh), 119.3, 111.4, 110.2 (cat′), 112.5 (=CH₂), 35.4 (Bu^t C), 32.1 (Bu^tCH₃). ¹¹B (90 °C), δ23.5. 3a: ¹H, δ7.6–6.9 (ov m, Ph + cat′, 13H), 5.19 (q, J 7, Hz, CHPh), 1.64 (d, J 7 Hz, 3H, CH₃), 1.29 (9H, Bu^t); ¹³C, δ 149.6, 147.5, 146.1, 144.6, 143.6 (ipso-C of CPh, NPh and cat′), 129.2, 129.0, 128.9, 127.9 (o-, m-C of NPh and CPh), 127.7, 126.2 (p-C of NPh and CPh), 118.9, 111.1, 109.8 (cat′), 58.4 (CN), 35.3 (Bu^t C), 32.1 (Bu^t CH₃), 20.0 (CH₃); ¹¹B (90 °C), δ26.3. 4a: ¹H, δ7.5–6.8 (ov m, Ph + cat′, 16H), 5.59 (‘tr’, J 8 Hz, CHPh), 2.25 (dd, J 16, 8.5 Hz, CH₂B), 2.12 (dd, J 16, 8 Hz, CH₂B), 1.30 (9H, Bu^t of NBcat′), 1.27 (9H, Bu^t of CBcat′); ¹³C, δ149.6, 149.2, 147.5, 147.0, 146.9, 146.0, 144.6, 143.5 (ipso-C of CPh, NPh, NBcat′ and CBcat′), 129.5, 129.2, 129.0, 128.1, (o-, m-C of NPh and CPh), 127.9, 126.5 (p-C of NPh and CPh), 119.9, 118.9, 111.8, 111.1, 110.3, 109.8 (cat′), 60.1 (CN), 35.4, 35.3 (Bu^t C), 32.1 (ov, 6C, Bu^t CH₃), 17.8 (br, CB); ¹¹B (90 °C), δ 35.7 (BC), 20.3 (BN). 5a: ¹H, δ7.6–6.9 (ov m, Ph + cat′, 19H), 6.06 (d, J 13 Hz, CHPh), 3.17 (d, J 13 Hz, CHB₂), 1.32 (9H, Bu^t of NBcat′), 1.26, 1.25 (9H, Bu^t of CBcat′); ¹³C, δ 62.2 (CN), 18.1 (br, CB).
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