Tetrahedron Letters 47 (2006) 7703–7705
Hydrogenation of olefins using water and zinc metal
catalyzed by a rhodium complex
Takashi Sato, Shoji Watanabe, Hiroyoshi Kiuchi, Shuichi Oi* and Yoshio Inoue*
Department of Biomolecular Engineering, Graduate School of Engineering, Tohoku University, Sendai 980-8579, Japan
Received 19 July 2006; revised 25 August 2006; accepted 30 August 2006
Available online 18 September 2006
Abstract—The hydrogenation of olefins using H2O or D2O as a hydrogen source and zinc metal as a reducing agent has been found
to be catalyzed by a rhodium complex. a,b-Unsaturated ketones also underwent hydrogenation, affording the corresponding satu-
rated ketones selectively.
Ó 2006 Elsevier Ltd. All rights reserved.
Transition-metal-catalyzed hydrogenation of carbon–
carbon multiple bonds is one of the most important
reactions in synthetic and industrial chemistry.1 Hydro-
gen gas is usually used in hydrogenation reactions;1
however, it requires the handling of a highly flammable
hydrogen gas and pressurized conditions. Although
metal hydrides, such as LiAlH4 and Bui2AlH, can be used
as the reducing agent,2 the cost and functional group
compatibility of metal hydride reagents often become
a problem. Typical metals, such as lithium, sodium,
and zinc, can be also used as the reducing agent for
the hydrogenation of carbon–carbon p-systems in the
presence of protic reagents, such as amines, alcohols,
acids, and water. However, these reagents are mainly
used in the selective reduction of alkynes to alkenes.2
Catalytic transfer hydrogenation using simple alcohols,
such as MeOH and PriOH, and transition metal cata-
lysts is an attractive method since it does not require
pressurized conditions and expensive reagents.3
Recently, Shirakawa, Hayashi, and co-workers have
reported the hydrogenation of alkynes to alkenes using
D2O or H2O as a hydrogen source and hexamethyldi-
silane as a reducing agent in the presence of palladium
catalyst.4 Here, we report a rhodium-catalyzed hydro-
genation of olefins including a,b-unsaturated ketones
using H2O or D2O as hydrogen source and zinc metal
as a reducing agent.
(2.0 mol %) and zinc powder (2.0 mmol) in water
(0.4 mL) and 1,4-dioxane (2.0 mL) at 90 °C for 20 h.5
No reaction was observed in the absence of rhodium
catalyst. Typical results are summarized in Table 1.
The terminal olefins including aromatic and aliphatic
ones afforded the saturated products in a quantitative
yield (entries 1–4). No olefin isomerized product was
observed in the case of aliphatic olefins. The reactions
of internal trans-olefins, such as trans-b-methylstyrene
and trans-stilbene, afforded the reduced products in
moderate yields of 53% and 33%, respectively (entries
5 and 6). On the other hand, the hydrogenation of cis-
stilbene proceeded smoothly affording the product in a
quantitative yield (entry 7). The reaction of indene also
proceeded to afford indan in 62% yield (entry 8).
a,b-Unsaturated ketones including cyclic ones also
underwent the present hydrogenation. In these cases,
1,4-reduced products were obtained selectively and no
alcohol product was observed. Typical results are
summarized in Table 2. The reactions of linear enones
examined afforded the corresponding ketones in a
quantitative yield (entries 1–3). Cyclic enones, such as
2-cyclohexenone and 3-methyl-2-cyclohexenone also
afforded the corresponding ketones in a quantitative
yield (entries 4 and 5). However, the reaction of 3,5,5-
trimethyl-2-cyclohexenone gave the product in a low
yield of 15% (entry 6). In this case, a steric hindrance
of the three methyl groups would slow the reaction.
The hydrogenation of olefins (1.0 mmol) was performed
in a Schlenk tube in the presence of [Rh(cod)Cl]2
The present hydrogenation can also be applicable to the
deuteration reaction using D2O instead of water. Thus,
the reaction of 1,3-diphenyl-2-propen-1-one in the pres-
ence of D2O afforded the 2,3-dideuterated ketone in a
Keywords: Hydrogenation; Alkene; a,b-Enone; Zinc metal; Rhodium
catalyst.
*
0040-4039/$ - see front matter Ó 2006 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tetlet.2006.08.107