Indium-mediated allylation of 1,2-diketones

Article abstract of DOI:10.1081/SCC-120001511

Indium-mediated allylation of 1,2-dicarbonyl compounds with indium and allylic bromides was achieved in the presence of nBu₄NI or NH₄Cl as additive to afford mono- and/or diallylated products in good yields.

Full text of DOI:10.1081/SCC-120001511

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INDIUM-MEDIATED ALLYLATION OF 1,2-DIKETONES
Suk-Ku Kang , Tae-Gon Baik a & Xiang-Hua Jiao a
a Department of Chemistry and Institute for Basic Sciences, Sungkyunkwan University ,
Suwoon, 440-746, Korea
Published online: 21 Aug 2006.
To cite this article: Suk-Ku Kang , Tae-Gon Baik & Xiang-Hua Jiao (2002) INDIUM-MEDIATED ALLYLATION OF 1,2-DIKETONES,
Synthetic Communications: An International Journal for Rapid Communication of Synthetic Organic Chemistry, 32:1,
75-78, DOI: 10.1081/SCC-120001511
To link to this article: http://dx.doi.org/10.1081/SCC-120001511
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SYNTHETIC COMMUNICATIONS, 32(1), 75–78 (2002)
INDIUM-MEDIATED ALLYLATION
OF 1,2-DIKETONES
Suk-Ku Kang,* Tae-Gon Baik, and Xiang-Hua Jiao
Department of Chemistry and Institute for Basic Sciences,
Sungkyunkwan University, Suwoon 440-746, Korea
ABSTRACT
Indium-mediated allylation of 1,2-dicarbonyl compounds
with indium and allylic bromides was achieved in the presence
of nBu4NI or NH4Cl as additive to afford mono- and/or
diallylated products in good yields.
Carbon–Carbon bond formation promoted by allyl metals is one of the
fundamental process in organic synthesis.1 Recently indium-mediated
Barbier-type allylation of variety of ketones and aldehydes in aqueous
medium received much attention.2 Li et al.3 reported the indium-mediated
allylation of enolizable 1,3-dicrabonyl compounds under aqueous medium.
However, to the best of our knowledge, allylation of 1,2-dicarbonlyl com-
pounds has not been known. Here we wish to report indium-mediated allyla-
tion of 1,2-carbonyl compounds in aqueous medium or methanol.
We selected phenylglyoxal as a substrate for allylation of 1,2-diketones
and reacted with indium and allylic bromides. As solvents, H2O, DMF,
DMF/H2O (1:1), THF, THF/H2O (1:1) were used, but the reactions were
sluggish. The addition of the additive was crucial. Thus by adding nBu4NI
*Corresponding author.
75
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KANG, BAIK, AND JIAO
(5 mol%) in H2O, we could get the monoallylated product 3a in 76% yield
(entry 1 in Table 1). With crotyl bromide, the mono-allylated product 3b
was afforded (entry 2). When NH4Cl was used as an additive in the reaction
of phenylglyoxal with allyl bromide in MeOH we could successfully get the
diallylated product 3c in 86% yield (entry 3). Crotyl bromide 2b and methal-
lyl bromide 2c were also treated with indium followed by glyoxal 1a to give
the diols 3b and 3e (entries 4 and 5). When this method was applied to 1,2
diketones, 1-phenyl-1,2-propandione (1b), a separable mixture of mono-
and diallylation products 3f (33%) and 3g (66%) were afforded (entry 6).
For benzil (1c) as a source of 1,2-diketones the reaction with allylic bromide
and indium provided mono-allylated product 31 as a sole product in 93%
yield (entry 9). With crotyl bromide and indium, the reaction of 1c provided
a mixture of unseparable cis and trans (79 : 21) adduct in 84% yield (entry
10).4 Finally, treatment of afforded 1c with indium and methallyl bromide
afforded 3n in 81% yield (entry 11). In summary we have successfully car-
ried out the reaction of 1,2-diketones with indium and allylic bromides by
adding additives to afford mono- and/or diallylated products.
EXPERIMENTAL SECTION
Typical Procedures
Method A: Preparation of 2-Hydroxy-1-phenyl-pent-4-en-1-one (3a).
To a stirred solution of nBu4NI (6.0 mg, 5 mol%) and indium (76 mg,
1.23 mmol) in H2O (10 mL) was added allyl bromide (120 mg, 1.82 mmol)
followed by phenylglyoxal (1a) (50 mg, 0.61 mmol) at room temperature
under N2 and the mixture was stirred at rt for 4 h. The reaction mixture
was extracted with ether (20 mL) and the organic layer was dried over
anhydrous MgSO4 and evaporated in vacuo. The crude product was sepa-
rated by SiO2 column chromatography (EtOAc:hexanes ¼ 1:10, Rf ¼ 0.21)
to afford the coupled product 3a (85 mg, 76%). TLC, SiO2, EtOAc : hexanes,
1
Rf ¼ 0.29. H NMR (500 MHz, CDCl3) d 2.37 (m, 1H), 2.70 (m, 1H), 3.74
(d, 1H, J ¼ 7.0 Hz), 5.00 (dd, 1H, J ¼ 1.3, 17.0 Hz), 5.18 (m, 1H), 5.80
(m, 1H), 7.25 (m, 2H), 7.63 (m, 1H), 7.92 (m, 1H). IR (neat) 3355, 1265,
1115 cmÀ1. MS (EI): m/e (relative intensity) ¼ 177 (0.37), 176 (Mþ, 2), 135
(25), 105 (100), 77 (30).
Method B: Preparation of 4-Phenyl-octa-1,7-diene-4,5-diol (3c). To a
stirred solution of NH4Cl (33 mg, 0.61 mmol) and indium (76 mg, 1.23 mmol)
in MeOH (10 mL) was added allyl bromide (120 mg, 1.82 mmol) followed by
phenylglyoxal (1a) (50 mg, 0.61 mmol) at room temperature under N2 and the
mixture was stirred at reflux for 6 h. The reaction mixture was extracted with

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INDIUM-MEDIATED ALLYLATION
77
Table 1. Indium-Mediated Allylation of 1,2-Dicarbonyl Compoundsa

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KANG, BAIK, AND JIAO
ether (20 mL) and the organic layer was dried over anhydrous MgSO4 and
evaporated in vacuo. The crude product was separated by SiO2 column
chromatography (EtOAc : hexanes ¼ 1:10, Rf ¼ 0.16) to afford the coupled
product 3c (85 mg, 86%). TLC, SiO2, EtOAc : hexanes, Rf ¼ 0.29. 1H NMR
(500 MHz, CDCl3) d 1.94 (m, 1H), 2.10 (m, 1H), 2.20 (br, 1H), 2.53 (br, 1H),
2.83 (m, 1H), 2.87(m, 1H), 3.80 (d, 1H, J ¼ 7.0 Hz), 5.00 ꢀ 5.47(m, 4H), 5.51
(m, 1H), 5.76 (m, 1H), 7.25 (m, 1H), 7.40 (m, 4H). IR (KBr) 3055, 1265,
1115 cmÀ1. MS (EI): m/e (relative intensity) ¼ 177 (Mþ-C3H5, 9), 147(17),
105 (100), 77 (12).
ACKNOWLEDGMENT
Generous financial support from KRF(2000-015-DP0262) and
KOSEF-CMDS (Center for Molecular Design and Synthesis) is gratefully
acknowledged. T. G. Baik thanks BK21 program for financial support.
REFERENCES
1. Yamamoto, Y.; Asao, N. Chem. Rev. 1993, 93, 2207–2293.
2. Reviews: (a) Cintas, P. Synthesis 1995, 1087–1096. (b) Li, C.-J. Chem.
Rev. 1993, 93, 2023–2035. (c) Chan, T.H.; Li, C.-J.; Lee, M.C.; Wei, Z.Y.
Can. J. Chem. 1994, 72, 1181–1192.
3. Li, C.-J.; Lu, Y.-Q. Tetrahedron Lett. 1995, 36, 2721–2724.
4. The cis and trans stereochemistry was determined by 500 MHz 1H NMR
spectrum.
Received in the Netherlands February 15, 2000

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