Palladium-Catalyzed Carbonylative Coupling and C–H Activation - New Trends in Cross-Coupling: Theory and Applications - page 486

Pd(OAc) 2 (5 mol%)
( t -Bu) 3 PHBF 4 (10 mol%)
pyridine (2 e quiv)
n -Bu 4 NCl (1 equiv)
dioxane, 150 °C, 20 min
Mo(CO) 6 (0.5 eq uiv)

O

X

19 examples
26-88%

R

R

X=Br,Cl

Scheme 10.12 Pd-catalysed carbonylative synthesis of indanones using microwave
irradiation.

Pd(PPh 3 ) 4 (10 mol%)
DiPEA (2 equiv)
CO (50 bar)
Toluene, 130 °C

I O

H

9 examples
55-91%

Scheme 10.13 Palladium-catalysed carbonylative Heck-type cyclization of alkyl
halides.

O

[(cinnamyl)PdCl] 2 (1 mol%)
dppp, toluene, NEt 3
100 °C, 20 h

ROTf CO

R

23 examples
yields up to 95%

R'

R'

R = Aryl
Vinyl

Scheme 10.14 Palladium-catalysed carbonylative Heck reaction of aryl triflates with
styrenes.

primary and secondary alkyl iodides in the presence of a palladium catalyst
under CO pressure yielded a variety of synthetically versatile enone products.
This novel palladium-catalysed Heck-type cyclization is a rare example
where unactivated alkyl halides with b-hydrogens were involved. Different
substituted alkenes were well tolerated and both monocyclic and bicyclic
carbocycles were easily accessed (Scheme 10.13).
Clearly, so far efforts in this area have been focused on intramolecular
carbonylative Heck reactions. A general intermolecular carbonylative coupling
of aryl halides or triflates with terminal olefins was not known until the recent
work of Beller's group. Initially, Beller and co-workers succeeded in carbo-
nylative Heck couplings of aryl triflates with styrenes. 19 Starting from readily
available aryl and alkenyl triflates, the corresponding unsaturated ketones are
obtained in good yields (Scheme 10.14). The products represent useful
building blocks for the synthesis of a variety of biologically active compounds.
Shortly afterwards, a more general palladium-catalysed carbonylative Heck
reaction of aryl halides was developed by the same group. 20 For the first time,
various aromatic and aliphatic alkenes were employed successfully in this
system and good yields of the corresponding a,b-unsaturated ketones were
obtained (41-90%). Starting from readily available aryl iodides and bromides,
interesting building blocks were obtained under mild conditions
(Scheme 10.15). With respect to the reaction mechanism, the aryl-palladium
and acyl-palladium complexes were characterized by X-ray diffraction and the