_P.-Powell-auth.-Principles-of-Organometallic-Chemistry-Springer-Netherlands-1988

Organotransition metal chemistry
~ (80%)
Br
Br
+
PhCH 2 ZnBr
Br
CH 2 Ph
(68%) +
Ar X
Organotin reagents are particularly versatile because they are inert to many
functional groups including -N0 2 , -CN, -OR, -C0 2 R, -COR and -CHO.
Typically the reactions are carried out under reflux in THF or chloroform. An acyl
chloride R 1 C0Cl can replace the hali de R 1 X, providing a route to ketones R 1 COR 2 •
The rate determining step in the cycle is probably the transfer of the group R 2 from
tin to palladium. This apparently involves electrophilic attack by the palladium
complex at the carbon atom bonded to tin. The rate of transfer ofR 2 from Bu~SnR 2
falls in the order R 2 = PhC=C- > PhCH=CH- > H 2 C=CH- > Ph­
> PhCH 2 > alkyl. It is therefore possible to use the readily accessible tributyltin
derivatives Bu~SnR 2 as only the one group of interest, R 2 , is transferred.
An alternative approach to ketones is to conduct the reaction between R 1 X and
R 2 M under an atmosphere of carbon monoxide. Pressures of at least 3 atm are
required and even so some direct product R 1 R 2 is sometimes obtained.
OSnMe3+~Cl
o
228
geranyl chloride
[Pd]
-co
d~
o
~gom aketone ( 92%)