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DOI: 10.1055/s-0030-1259505
Regioselective Ring-Opening Reaction of Unsymmetrical 2,3-Diaryl Epoxides via Catalytic Hydrogenolysis with Pd(0)EnCatTM
Publication History
Publication Date:
25 January 2011 (online)

Abstract
A series of unsymmetrical 2,3-diaryl epoxides were hydrogenated under transfer-hydrogenation conditions using the polyurea-encapsulated palladium catalyst [Pd(0)EnCatTM]. The position of the cleaved C-O bond was determined by ¹H NMR analysis of the ring-opened products derived from the epoxide, in which one of the two benzylic methyne protons is deuterated. The ratio of ring-opened products of the unsymmetrically substituted 2,3-diaryl epoxides was affected by the degree of the steric bulkiness on the aromatic ring.
Key words
reductive ring-opening reaction - polyurea-encapsulated palladium catalyst [Pd(0)EnCatTM] - 2,3-diary epoxide - Darzens reaction
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References and Notes
Typical Procedure
for the Reductive Ring-Opening Reaction of the Epoxides 4-11
and Deuterated Epoxides (4-
d
-11-
d
)
Pd(0) catalyst [Pd(0)EnCatTM,
50 mg, 0.02 mmol] was added to a solution of the epoxide
(0.38 mmol) in EtOAc (0.75 mL) at r.t. under argon atmosphere. The
mixture was cooled to 0 ˚C, Et3N (0.28
mL, 4 mmol) and formic acid (0.07 mL, 4 mmoL) were added. After
5 h stirring at r.t., the mixture was worked up as follows. The
resulting Pd(0) was filtered off, then filtrate was concentrated
under reduced pressure. The remaining residue was purified by flash
chromatography to afford the product.
¹
H NMR Spectra of the Ring-Opened Products 12-21
Product 12: ¹H NMR (400 MHz,
CDCl3): δ = 1.65 (s, 1 H), 2.35 (s,
3 H), 2.91-3.06 (m, 2 H), 4.85-4.89 (m, 1 H),
7.10-7.36 (m, 9 H).
Product 13: ¹H
NMR (400 MHz, CDCl3): δ = 1.90 (s,
1 H), 3.00 (m, 2 H), 3.80 (s, 3 H), 4.84 (dd, 1 H, J = 5.9,
7.3 Hz), 6.85-6.89 (m, 2 H), 7.16-7.34 (m, 7 H).
Product 14: ¹H NMR (500 MHz,
CDCl3): δ = 1.11 (m, 3 H), 1.22 (m,
3 H), 2.97 (dd, 1 H, J = 8.2,
13.7 Hz), 3.03 (dd, 1 H, J = 5.0,
13.7 Hz), 3.25 (m, 2 H), 3.53 (m, 2 H), 4.91 (dd, 1 H, J = 5.0, 8.2
Hz), 7.16-7.36 (m, 9 H).
Product 15: ¹H
NMR (400 MHz, CDCl3): δ = 1.60 (s,
9 H), 2.97 (dd, 1 H, J = 8.4,
13.9 Hz), 3.04 (dd, 1 H, J = 4.8,
13.9 Hz), 4.95 (m, 1 H), 7.16-7.18 (m, 2 H), 7.22-7.32
(m, 3 H), 7.38 (d, 2 H, J = 8.4
Hz), 7.95 (d, 2 H, J = 8.4
Hz).
Product 16: ¹H
NMR (400 MHz, CDCl3): δ = 1.32 (s,
9 H), 1.89 (s, 1 H), 2.97 (dd, 1 H, J = 10.2,
13.5 Hz), 3.04 (dd, 1 H, J = 4.4,
13.5 Hz), 4.86 (m, 1 H), 7.20-7.30 (m, 5 H), 7.31 (d, 2
H, J = 8.4
Hz), 7.37 (d, 2 H, J = 8.4
Hz).
Product 17: ¹H
NMR (400 MHz, CDCl3): δ = 2.1 (d, 1
H, J = 3.0
Hz), 2.94 (dd, 1 H, J = 8.4,
13.5 Hz), 3.03 (dd, 1 H, J = 4.8,
13.5 Hz), 4.95 (m, 1 H), 7.14-7.36 (m, 5 H), 7.43 (d, 2
H, J = 8.0
Hz), 7.61 (d, 2 H, J = 8.0
Hz).
Product 18: ¹H
NMR (400 MHz, CDCl3): δ = 1.98 (m,
1 H), 3.05 (m, 1 H), 3.13 (m, 1 H), 4.90 (m, 1 H), 7.24-7.36
(m, 5 H), 7.27 (d, 2 H, J = 8.3
Hz), 7.54 (d, 2 H, J = 8.3
Hz).
Product 19: ¹H
NMR (500 MHz, CDCl3): δ = 3.07 (d,
2 H, J = 6.4
Hz), 5.00 (t, 1 H, J = 6.4
Hz), 7.27 (d, 2 H, J = 8.2 Hz),
7.42 (d, 2 H, J = 8.2
Hz), 7.57 (d, 2 H, J = 8.2
Hz), 7.60 (d, 2 H, J = 8.2
Hz).
Product 20: ¹H
NMR (400 MHz, CDCl3): δ = 2.89 (dd,
1 H, J = 8.4,
13.9 Hz), 2.99 (dd, 1 H, J = 4.8,
13.5 Hz), 3.79 (s, 3 H), 4.91 (m, 1 H), 6.84 (d, 2 H, J = 8.4 Hz),
7.08 (d, 2 H, J = 8.4
Hz), 7.45 (d, 2 H, J = 8.1
Hz), 7.59 (d, 2 H, J = 8.1 Hz).
Product 21: ¹H NMR (400 MHz,
CDCl3): δ = 3.04-3.08 (m, 2
H), 3.81 (s, 3 H), 4.86 (m, 1 H), 6.87 (d, 2 H, J = 8.8
Hz), 7.22-7.28 (m, 4 H), 7.52 (d, 2 H, J = 8.1
Hz).
¹
H NMR Spectra of Deuterated Ring-Opened Products 12-
d
-21-
d
Product 12-d: ¹H NMR (400 MHz,
CDCl3): δ = 2.34 (s, 3 H), 2.94-3.01
(m, 1 H), 4.83-4.85 (m, 1 H), 7.06-7.36 (m, 10 H).
Product 13-d: ¹H
NMR (400 MHz, CDCl3): δ = 3.00 (s,
2 H), 3.80 (s, 3 H), 6.87 (d, 2 H, J = 8.8
Hz), 7.26 (d, 2 H, J = 8.8 Hz),
7.16-7.30 (m, 5 H).
Product 14-d: ¹H NMR (400 MHz,
CDCl3): δ = 1.14 (m, 3 H), 1.22 (m,
3 H), 2.05 (s, 1 H), 3.02 (d, 1 H, J = 4.4
Hz), 3.27 (m, 2 H), 3.53 (m, 2 H), 4.92 (d, 1 H, J = 4.4
Hz), 7.17-7.38 (m, 9 H).
Product 15-d: ¹H NMR (400 MHz,
CDCl3): δ = 1.60 (s, 9 H), 1.99 (d,
1 H, J = 3.2
Hz), 3.02 (d, 1 H, J = 4.6
Hz), 4.95 (m, 1 H), 7.15-7.18 (m, 2 H), 7.22-7.32
(m, 3 H), 7.38 (d, 2 H, J = 8.2
Hz), 7.95 (d, 2 H, J = 8.2
Hz).
Product 16-d: ¹H
NMR (400 MHz, CDCl3): δ = 1.31 (s,
9 H), 1.89 (s, 1 H), 3.04 (d, 1 H, J = 4.4
Hz), 4.86 (d, 1 H, J = 4.4 Hz),
7.20-7.30 (m, 5 H), 7.31 (d, 2 H, J = 8.4
Hz), 7.37 (d, 2 H, J = 8.4
Hz).
Product 17-d: ¹H
NMR (400 MHz, CDCl3): δ = 2.07 (d,
1 H, J = 3.2
Hz), 3.01 (m, 1 H), 4.95 (m, 1 H), 7.27-7.40 (m, 5 H), 7.43
(d, 2 H, J = 8.3
Hz), 7.62 (d, 2 H, J = 8.3
Hz).
Product 18-d: ¹H
NMR (400 MHz, CDCl3): δ = 2.00 (br
s, 1 H), 3.05 (m, 1 H), 3.10 (m, 1 H), 7.37 (m, 5 H), 7.30 (d, 2
H, J = 8.3
Hz), 7.55 (d, 2 H, J = 8.3
Hz).
Product 19-d: ¹H
NMR (400 MHz, CDCl3): δ = 1.96 (s,
1 H), 3.07 (s, 2 H), 7.27 (d, 2 H, J = 8.1
Hz), 7.42 (d, 2 H, J = 8.1 Hz),
7.56-7.65 (m, 4 H).
Product 20-d: ¹H NMR (400 MHz,
CDCl3): δ = 1.98 (d, 1 H, J = 3.3 Hz),
2.98 (m, 1 H), 3.79 (s, 3 H), 4.91 (s, 1 H), 6.85 (d, 2 H, J = 8.1 Hz),
7.08 (d, 2 H, J = 8.1
Hz), 7.45 (d, 2 H, J = 8.4
Hz), 7.59 (d, 2 H, J = 8.4
Hz).
Product 21-d: ¹H
NMR (400 MHz, CDCl3): δ = 1.81 (s,
1 H), 3.06 (dd, 2 H, J = 13.5,
23.8 Hz), 3.81 (s, 3 H), 6.88 (d, 2 H, J = 8.8
Hz), 7.24 (d, 2 H, J = 8.8
Hz), 7.27 (d, 2 H, J = 8.1 Hz),
7.53 (d, 2 H, J = 8.1
Hz).