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DOI: 10.1055/s-0030-1289519
Cationic Palladium(II)-Catalyzed Synthesis of 2-Substituted 3-Hydroxymethylbenzo[b]furans
Publication History
Publication Date:
06 October 2011 (online)
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Abstract
A tandem reaction involving an intramolecular oxypalladation of an alkyne and an addition to the carbonyl group to quench the carbon-palladium bond to complete the catalytic cycle was developed. The reaction was catalyzed with the cationic palladium(II) species without the necessity of a redox system.
Key words
aldehyde - alkyne - cationic palladium(II) complex - 3-hydroxymethylbenzofuran - oxypalladation
- Supporting Information for this article is available online:
- Supporting Information
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References and Notes
General Procedure
for the Synthesis of 2-Substituted 3-Hydroxymethylbenzofuran
Catalyzed by [Pd(dppp)(H
2
O)
2
](BF
4
)
2
A
dried small tube with screw-cap was charged with [Pd(dppp)(H2O)2](BF4)2 (1.2
mg, 0.002 mmol), 4 Å MS
(20 mg), THF (0.5 mL),
then substrates 1 (0.1 mmol) and aldehydes 2 (0.2 mmol, 2 equiv) were added to the
mixture, and the solution was stirred at 45 ˚C
until complete consumption of substrates 1 (monitored
by TLC). Then,
the mixture was concentrated under reduced
pressure and purified by flash column chromatography on silica gel
using
EtOAc and PE as the eluent to afford the product.
Compound 3aa: solid; mp 87-89 ˚C. ¹H
NMR (400 MHz, CDCl3): δ = 8.16 (d, J = 8.8 Hz,
2 H), 7.77 (d, J = 6.8
Hz, 2 H), 7.65 (d, J = 8.4
Hz, 2 H), 7.52-7.45 (m, 4 H), 7.28-7.23 (m, 1
H), 7.19 (d, J = 7.6
Hz, 1 H), 7.08 (t, J = 7.6
Hz, 1 H), 6.39 (s, 1 H), 2.61 (d, J = 3.6
Hz, 1 H). ¹³C NMR (75 MHz, CDCl3): δ = 154.3,
153.5, 149.1, 147.1, 129.7, 129.5, 129.0, 127.7, 126.9, 124.9, 123.0,
121.0, 116.2, 111.4, 67.7. IR (KBr): ν = 3349,
3065, 1600, 1518, 1453, 1344, 1027, 834, 746 cm-¹.
MS (EI): m/z (%) = 345
(100) [M+], 328, 223, 165, 105,
77, 57. HRMS (EI): m/z calcd
for C21H15NO4: 345.1001; found:
345.1005.