Palladium-Catalyzed Carbonylative Coupling and C–H Activation - New Trends in Cross-Coupling: Theory and Applications - page 490

O

I Pd(OAc) 2 (5 mol%)

PPh 3 ,NEt 3 ,PhH
CO (21-84 bar)
110-120 °C

O

12 examples
35-88%

R

R'

R'

R

Scheme 10.21 Pd-catalysed carbonylation of benzylacetylenes to give furanones.

Pd(OAc) 2 (3 mol %),
dppp, NEt 3 ,DMF
CO (1 bar)
60 °C

O

OTf

R 15 examples

53-83 %

R

Scheme 10.22 Pd-catalysed carbonylative Sonogashira coupling of vinyl triflates
with 1-alkynes.

O

I

[(Ph 3 P)Pd(Ph)(OH)] 2 (1 mol%)
CO (17 bar)
NEt 3 , 90 °C

20 examples
43-94 %

R'

R'

R

R

Scheme 10.23 Dimeric palladium hydroxide-catalysed carbonylative Sonogashira
coupling.

Interestingly, in 1991, Huang and Alper reported another type of pal-
ladium-catalysed carbonylative Sonogashira coupling of aryl iodides with
benzyl acetylenes, where furanones were isolated as terminal products and
not the predicted alkynones. 29a In the presence of Pd(OAc) 2 /PPh 3 , aryl iod-
ides and benzylacetylenes were transformed into furanones in 33-88% yields
(Scheme 10.21). Later, Beller's group proved that this transformation can be
done at room temperature under 1 bar of CO. 29b They also extended their
methodology to aryl bromides and benzyl chlorides. 29c,d Palladium-catalysed
carbonylative Sonogashira coupling reactions of iodobenzene and 2-methyl-
3-butyn-2-ol under biphasic conditions yielding furanones were also re-
ported by Kiji et al. 29e
In 1991, Ortar and co-workers published a general procedure for carbo-
nylative Sonogashira couplings of vinyl triflates with terminal acetylenes. 30
Various alkynyl ketones were produced in moderate to good yields
(Scheme 10.22). However, this methodology failed in the case of activated
alkynes or aryl triflates.
The catalytic ability of dimeric palladium hydroxide in carbonylative
Sonogashira coupling was demonstrated by Alper and co-workers in 1994. 31
In this report, terminal alkynes and alkynols were coupled with aryl iodides
in the presence of carbon monoxide with moderate to good yields
(Scheme 10.23).
In 1995, Cacchi and co-workers presented a general methodology for
the synthesis of 5-(2-acylethynyl)-3 0 ,5 0 -di-O-acetyl-2 0 -deoxyuridines. 32

In the