The Journal of Organic Chemistry
Article
IR (DCM): 2977, 1455, 1372, 1273, 1216, 1146, 1060, 1009, 943,
924, 852, 743, 701, 676 cm−1. 1H NMR (CDCl3): δ 7.31 (d, 1H, J = 4
Hz), 7.12 (d, 1H, J = 4 Hz), 7.10 (s, 1H), 3.29−3.32 (m, 2H), 2.80−
2.83 (m, 2H), 1.16 (s, 24H). 13C {1H} NMR (CDCl3): δ 136.8, 135.3,
132.4, 132.1, 129.0, 126.7, 82.2, 43.2, 36.2, 24.5. 11B{1H} NMR
(CDCl3): δ 25.7 (s, B-N). HRMS (EI) m/z calcd for C8H10Cl2N
(Fragment): (M−C12H24B2O4+H)+ 190.0186, found: 190.0156.
N-Butyl-4,4,5,5-tetramethyl-N-(4,4,5,5-tetramethyl-1,3,2-dioxa-
borolan-2-yl)-1,3,2-dioxaborolan-2-amine (4i).26 IR (DCM): 2973,
2937, 1462, 1454, 1274, 1170, 1059, 963, 941, 765, 750, 677 cm−1. 1H
NMR (CDCl3): δ 3.00 (t, 2H, J = 8 Hz), 1.32−1.37 (m, 4H), 1.20 (s,
24H), 0.86 (t, 3H, J = 8 Hz). 13C {1H} NMR (CDCl3): δ 82.0, 43.3,
35.4, 24.6, 19.7, 14.1. 11B{1H} NMR (CDCl3): δ 25.6 (s, B-N). HRMS
(EI) m/z calcd for C4H11NNa: (M−C12H24B2O4+Na)+: 96.0784,
found: 96.0781.
Scheme 1. Chemoselective Hydroboration of Nitrile to
Diboronate Amines
4,4,5,5-Tetramethyl-N-octyl-N-(4,4,5,5-tetramethyl-1,3,2-dioxa-
borolan-2-yl)-1,3,2-dioxaborolan-2-amine (4j). IR (DCM): 2922,
1
1453, 1371, 1271, 1166, 1069, 1009, 941, 723, 702, 678 cm−1. H
NMR (CDCl3): δ 2.99−3.00 (m, 2H), 1.22−1.25 (m, 12H), 1.20 (s,
24H), 0.85 (t, 3H, J = 8 Hz). 13C {1H} NMR (CDCl3): δ 82.1, 43.7,
33.1, 32.0, 29.6, 29.4, 26.7, 24.6, 22.8, 14.2. 11B{1H} NMR (CDCl3): δ
25.6 (s, B-N). HRMS (EI) m/z calcd for C8H20N (Fragment): (M-
C12H24B2O4+H)+ 130.1596, found: 130.1587.
4,4,5,5-Tetramethyl-N-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-
2-yl)-N-undecyl-1,3,2-dioxaborolan-2-amine (4k). IR (DCM): 2931,
1444, 1370, 1259, 1179, 1061, 978, 757, 663 cm−1. 1H NMR (CDCl3):
δ 2.96−2.99 (m, 2H), 1.20−1.23 (m, 20H), 1.18 (s, 24H), 0.83−0.86
(m, 3H). 13C {1H} NMR (CDCl3): δ 82.0, 43.6, 33.1, 32.0, 29.8, 29.7,
29.6, 29.4, 26.6, 24.5, 22.7, 14.2. 11B{1H} NMR (CDCl3): δ 25.6 (s, B-
N). HRMS (EI) m/z calcd for C12H28N (Fragment): (M−
C12H24B2O4+H)+ 186.2222, found: 186.2201.
N-Ethyl-4,4,5,5-tetramethyl-N-(4,4,5,5-tetramethyl-1,3,2-dioxa-
borolan-2-yl)-1,3,2-dioxaborolan-2-amine (4l). IR (DCM): 2972,
1
1453, 1372, 1220, 1165, 1093, 1059, 943, 922, 678 cm−1. H NMR
(CDCl3): δ 3.06 (quat, 2H, J = 8 Hz), 1.22 (s, 24H), 1.03 (t, 3H, J = 8
Hz). 13C {1H} NMR (CDCl3): δ 82.1, 38.7, 24.6, 18.7. 11B{1H} NMR
(CDCl3): δ 25.6 (s, B-N). HRMS (EI) m/z calcd for C14H30B2NO4:
(M+H)+ 298.2361, found: 298.2378.
N-Ethyl-4,4,5,5-tetramethyl-N-(4,4,5,5-tetramethyl-1,3,2-dioxa-
Figure 2. 1H NMR monitoring of the reaction progress: 4-
methoxybenzonitrile (0.25 mmol), pinacolborane (0.55 mmol), 1
(0.0025 mmol), and C6D6 were charged in a screw cap NMR tube and
monitored at regular interval. % Conversion is determined from
borolan-2-yl)-1,3,2-dioxaborolan-2-amine-d3 (4m). IR (DCM):
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2972, 1446, 1385, 1272, 1162, 1061, 1003, 944, 917, 681 cm−1. H
NMR (CDCl3): δ 3.05 (s, 2H, CH2), 1.24 (s, 24H, CH3). 13C {1H}
NMR (CDCl3): δ 81.94 (quat-C), 38.35 (CH2), 24.50 (CH3), 17.30−
17.74 (m, CD3). 11B{1H} NMR (CDCl3): δ 25.69 (s, B-N). HRMS
(EI) m/z calcd for C8H13D3BNO2: (M−C6H12BO2−H)+ 172.1458,
found: 172.1462.
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integration of H NMR.
calcd for C15H23BNO4Na (Fragment): (M−C6H12BO2+Na)+
315.1618, found: 315.1639.
N,N′-(1,3-Phenylenebis(ethane-2,1-diyl))bis(4,4,5,5-tetramethyl-
N-(4,4,5,5-tetramethyl-1,3,2 dioxaborolan-2-yl)-1,3,2-dioxaboro-
lan-2-amine) (4n). IR (DCM): 2975, 1591, 1454, 1372, 1272, 1217,
4,4,5,5-Tetramethyl-N-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-
2-yl)-N-(4-(((4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)oxy)-
methyl)benzyl)-1,3,2-dioxaborolan-2-amine (4f). IR (DCM): 2977,
1454, 1371, 1273, 1217, 1167, 1146, 1057, 981, 944, 924, 852, 699,
676 cm−1. 1H NMR (CDCl3): δ 7.24−7.30 (m, 4H), 4.90 (s, 2H), 4.24
(s, 2H), 1.28 (s, 12 H), 1.21 (s, 24H).13C {1H} NMR (CDCl3): δ
142.4, 137.0, 127.5, 126.5, 83.0, 82.4, 66.8, 47.1, 24.7, 24.6. 11B{1H}
NMR (CDCl3): δ 25.9 (s, B-N), 25.8 (s, B-O). HRMS (EI) m/z calcd
for C14H20BO3 (Fragment): (M- C12H24B2NO4)+: 247.1506, found:
247.1491.
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1147, 1060, 981, 924, 852, 792, 736, 676 cm−1. H NMR (CDCl3): δ
7.11−7.12 (m, 2H), 6.97−6.99 (m, 2H), 3.27 (t, 4H, J = 8 Hz), 2.65−
2.68 (m, 4H), 1.19 (s, 48H). 13C{1H} NMR (CDCl3): δ 140.2, 130.0,
127.9, 126.6, 82.1, 45.3, 39.6, 24.6. 11B{1H} NMR (CDCl3): δ 25.5 (s,
B-N). HRMS (EI) m/z calcd for C10H17N2: (M−C12H24B2O4+5H)+
165.1392, found: 165.1382.
N,N′-(1,4-Phenylenebis(ethane-2,1-diyl))bis(4,4,5,5-tetramethyl-
N-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)-1,3,2-dioxaboro-
lan-2-amine) (4o). IR (DCM): 2979, 1453, 1373, 1288, 1169, 1056,
981, 945, 924, 852, 784, 676 cm−1. 1H NMR (CDCl3): δ 7.07 (s, 4H),
3.23 (t, 4H, J = 8 Hz), 2.64 (t, 4H, J = 8 Hz), 1.18 (s, 48H). 13C {1H}
NMR (CDCl3): δ 137.8, 129.0, 82.1, 45.5, 39.3, 24.6. 11B{1H} NMR
(CDCl3): δ 25.5 (s, B-N). HRMS (EI) m/z calcd for C10H17N2
(Fragment): (M−C12H24B2O4+H)+ 165.1392, found: 165.1381.
General Procedure for Imine Hydroboration. Imine (1 mmol),
pinacolborane (1 mmol), [Ru(p-cymene)Cl2]2 (0.1 mol %) [toluene
(0.5 mL) for solid substrates], and a magnetic bead were charged in a
PTFE screw-capped reaction vial under nitrogen atmosphere. The
reaction mixture was heated to 60 °C for 15 h. Progress of the reaction
N-(3-(2-Chlorophenyl)propyl)-4,4,5,5-tetramethyl-N-(4,4,5,5-tet-
ramethyl-1,3,2-dioxaborolan-2-yl)-1,3,2-dioxaborolan-2-amine
(4g). The compound 4g was isolated by crystallization (hexane/DCM)
of the crude solid obtained from filtration through a Celite pad. Yield
290 mg, 69%. IR (DCM): 2976, 2930, 1475, 1453, 1372, 1272, 1217,
1167, 1055, 1009, 924, 852, 752, 699, 676 cm−1. 1H NMR (CDCl3): δ
7.32−7.34 (m, 1H), 7.26−7.28 (m, 1H), 7.19−7.21 (m, 1H), 7.12−
7.15 (m, 1H), 3.17 (t, 2H, J = 8 Hz), 2.68−2.74 (m, 2H), 1.76 (t, 2H, J
= 8 Hz), 1.25 (s, 24H). 13C{1H} NMR (CDCl3): δ 140.6, 134.1, 130.1,
129.4, 127.0, 126.7, 82.2, 43.6, 32.8, 30.9, 24.6. 11B{1H} NMR
(CDCl3): δ 25.9 (s, B-N). HRMS (EI) m/z calcd for C15H22BClNO2:
(M−C6H12BO2)+: 294.1432, found: 294.1425.
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was monitored by H NMR. Upon completion, the reaction mixture
was treated with silica gel (500 mg, 100−200 mesh) and methanol at
50 °C for 6 h. The completion of hydrolysis was monitored by TLC.
N-(2,4-Dichlorophenethyl)-4,4,5,5-tetramethyl-N-(4,4,5,5-tetra-
methyl-1,3,2-dioxaborolan-2-yl)-1,3,2-dioxaborolan-2-amine (4h).
F
J. Org. Chem. XXXX, XXX, XXX−XXX