Abstract
A generally applicable method for the introduction of gaseous hydrogen into a sealed reaction system to perform hydrogenation reactions under microwave irradiation has been developed. Several different types of substrates are easily reduced in short reaction times with moderate temperatures between 80 °C and 100 °C with 50 psi of hydrogen. The use of simultaneous cooling is also applied to the hydrogenation of more difficult substrates.
Key words
hydrogenations - microwave - palladium - reductions - simultaneous cooling
References and Notes
For reviews on microwave chemistry, see:
1a
Hayes BL.
Microwave Synthesis: Chemistry at the Speed of Light
CEM Publishing;
Matthews, NC:
2002.
1b
Loupy A.
Microwaves in Organic Synthesis
Wiley-VCH;
Weinheim, Germany:
2002.
1c
Microwave Assisted Organic Synthesis
Tierney JP.
Lidström P.
Blackwell Publishing;
Oxford, UK:
2005.
1d
Kappe CO.
Stadler A.
Microwaves in Organic and Medicinal Chemistry
Wiley-VCH;
Weinheim, Germany:
2005.
2a
Dayal B.
Ertel NH.
Rapole KR.
Asgaonkar A.
Salen G.
Steroids
1997,
62:
451
2b
Banik BK.
Barakat KJ.
Wagle DR.
Manhas MS.
Bose AK.
J. Org. Chem.
1999,
64:
5746
2c
Daga MC.
Taddei M.
Varchi G.
Tetrahedron Lett.
2001,
42:
5191
2d
Berthold H.
Schotten T.
Hönig H.
Synthesis
2002,
1607
2e
Stiasni N.
Kappe CO.
ARKIVOC
2002,
(viii):
71
3a
Desai B.
Danks TN.
Tetrahedron Lett.
2001,
42:
5963
3b
Danks TN.
Desai B.
Green Chem.
2002,
4:
179
4
Arcadi A.
Cerichelli G.
Chiarini M.
Vico R.
Zorzan D.
Eur. J. Org. Chem.
2004,
3404
5a
Lutsenko S.
Moberg C.
Tetrahedron: Asymmetry
2001,
12:
2529
5b
Reetz MT.
Li X.
J. Am. Chem. Soc.
2006,
128:
1044
6
Akisanya J.
Danks TN.
Garman RN.
J. Organomet. Chem.
2000,
603:
240
7a
Wada Y.
Yin H.
Kitamura T.
Yanagida S.
Chem. Lett.
2000,
632
7b
Pillai UR.
Sahle-Demessie E.
Varma RS.
Green Chem.
2004,
6:
295
8a
Heller E.
Lautenschläger W.
Holzgrabe U.
Tetrahedron Lett.
2005,
46:
1247
8b
Gustafssön T.
Hedenstrom M.
Kihlberg J.
J. Org. Chem.
2006,
71:
1911
9
Experimental Set-up.
All reactions were performed with a CEM Discover single mode microwave reactor equipped with a 300 W power source. A 10 mL fiber optic accessory was equipped with a gas inlet to allow introduction of hydrogen gas to the reaction vessel, and each of the reactions was performed in a CEM 10 mL microwave reaction vial. All temperature measurements were performed with a fiber optic probe, and 2 mL of solvent was used for each reaction to ensure ample submersion of the fiber optic probe.
General Procedure.
To a solution of trans,trans-1,4-diphenyl-1,3-butadiene (1, 103 mg, 0.500 mmol) in 2.0 mL of EtOAc was added Pd/C (10 wt%, 5 mg, 0.005 mmol). The reaction vessel was purged three times with hydrogen, charged to 50 psi, and then closed off to the source of hydrogen. The reaction was heated under microwave irradiation to 80 °C with 100 W of power and held for 5 min. Upon cooling to ambient temperature, the reaction mixture was filtered through Celite® and condensed to give 105 mg (>99%) of 1,4-diphenylbutane. 1H NMR (400 MHz, CDCl3): δ = 7.23-7.27 (m, 4 H), 7.14-7.17 (m, 6 H), 2.62 (t, J = 6.6 Hz, 4 H), 1.65 (dt, J = 7.2, 3.8 Hz, 4 H). 13C NMR (100 MHz, CDCl3): δ = 142.66, 128.53, 128.38, 125.77, 35.93, 31.20. Characterization data is consistent with that of commercially available material.
10
Whittaker AG.
Mingos DMP.
J. Chem. Soc., Dalton Trans.
2000,
1521
11 Isolated yields were difficult due to the low volatility of the products.
12a
Katritzky AR.
Zhang Y.
Singh SK.
Steel PJ.
ARKIVOC
2003,
(xv):
47
12b
Chen JJ.
Deshpande SV.
Tetrahedron Lett.
2003,
44:
8873
12c
Arvela RK.
Leadbeater NE.
Org. Lett.
2005,
7:
2101
