C O M M U N I C A T I O N S
Table 3. Reaction of Various Alcohols with 2 Catalyzed by 1a
Scheme 2. Possible Reaction Path
with isopropenyl acetate under these conditions afforded isopropenyl
n-octyl ether in 78% yield (run 12).
To obtain mechanistic information, phenol-d (20-d) was allowed
to react with 2 under these conditions.11 It was found that no
deuterium was introduced into the resulting phenyl vinyl ether. This
may suggest the following reaction path through an intermediate
A resulted from the reaction of 1 with vinyl acetate 2 and alcohol
3 under the influence of Na2CO3 (Scheme 2). The release of an
alkyl vinyl ether 4 from the intermediate A gives rise to an iridium
acetoxy complex B, which then reacts with alcohol 3, leading to
an iridium alkoxy complex C, and the coordination of the vinyl
acetate 2 to the complex C followed by insertion regenerates the
A.
In conclusion, a versatile synthetic method for a wide variety of
vinyl ethers, which are very difficult to prepare thus far, through
the addition-elimination sequence of alcohol and acetic acid using
iridium complex as a catalyst has been developed.
Supporting Information Available: Experimental procedures and
spectral data for compounds 11, 19, and 25 (PDF). This material is
References
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a Substrate (1.0 mmol) was allowed to react with 2 (2 mmol) in the
presence of 1 (0.01 mmol) and Na2CO3 (0.6 mmol) in toluene (1 mL) at
100 °C under Ar. b 2 (4 mmol). c NaOAc (1.2 mmol) was used instead of
Na2CO3. d 2 (3 mmol). e 1 (0.02 mmol), 2 (5 mmol), and Na2CO3 (1.2
mmol). f 1 (1.04 µmol) was used. At 110 °C for 5 h. g 20 (100 mmol) was
allowed to react with 2 (200 mmol) in the presence of 1 (1 mmol) and
Na2CO3 (60 mmol) in toluene (100 mL) at 100 °C under Ar. h NaOAc (0.03
mmol) was used instead of Na2CO3. i Isopropenyl acetate (2 mmol) was
used instead of 2.
reacted with 2 under these conditions to afford 1,6-divinyloxyhexane
(8) in good yield (87%) along with 6-vinyloxyhexyl alcohol (9)
(2%) (run 2). Triethylenglycol (10) gave the corresponding divinyl
ether, 11, in good yield (run 3). The present catalytic system was
found to be applicable to the synthesis of vinyl ethers from 2 and
secondary and tertiary alcohols (runs 4-11). Thus, 1-adamantyl
vinyl ether (17) was obtained from adamantanol (16) and 2 in 91%
yield (run 6). Similarly, the reaction of phenol (20) with 2 produced
the desired vinyl ether (21) in excellent yield (98%) (run 8). The
reaction was found to take place with high turnover number (766).
Additionally, a large-scale experiment was run. The reaction of 100
mmol (9.4 g) of 20 with 2 equiv of 2 under the same reaction
conditions gave 21 in almost the same yield. It is noteworthy that
thiophenol (26) reacted with 2 to form thiophenyl vinyl ether (27)
in 92% yield (run 11), although sulfur compounds frequently inhibit
transition metal-catalyzed reactions. In addition, the reaction of 3
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(11) AcOD was formed in this reaction. The formation of AcOD was confirmed
by the conversion of AcOD to 1-acetoxy-2-deuterio-1-ethoxyoctane by
the reaction with octyl vinyl ether without any catalyst.
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