Modern Heck Reactions - New Trends in Cross-Coupling: Theory and Applications - page 399

Ph

Br Ph

Pd 2 (dba) 3 (0.0 001 mol% )
(19) ,NaOAc,Bu 4 NBr
NMP, MW 200°C, 2 h

MeO MeO

74 %
TON 740,000

N N

S

O -

(19)

Scheme 9.63 High-TON arylation of styrene by an electron-rich aryl bromide in the
presence of ligand 19.

Py

PhSe Pd SePh

PhSe
Pd
PhSe

SePh

Pd

SePh

(ClO 4 ) 2

PhSe Pd SePh

(21)

(BF 4 ) 2

Py

(20)

Scheme 9.64 Two precatalysts of similar catalytic activity formed from the same
tetraselenide chelator.

CH 2 =CH 2
NC-palladacycle
(0.0 13 mol% Pd)
base, solvent
110°C, 1.5 h
b ase (yield) = NaOAc (98 %), KOA c (97% ), Na 3 PO 4 (84 %), K 2 CO 3 (7 7%),
Cs 2 CO 3 (7 0%), iPr 2 NH (68%) >> Et 3 N, C aO, N a 2 CO 3
solvent = NMP, DMF, DMA

Br

MeO MeO

OTs PPh 3

OTs

Pd

N O N Pd PPh 3

OTs

N

Pd

NMe 2

PPh 3

Pd

PPh 3

Ts O

Scheme 9.65 Monoarylation of ethylene giving naproxen precursor: a comparative
study using N,C-palladacycles.

Se-Se chelate - the catalytic activity (yields, TON and TOF values) were
closely similar, thus showing once again that catalytic activity is associated
not with the structure of the precatalyst, but rather with the composition of
the catalytic system.
A study giving an unambiguous example of the typical operation of a
catalytic system based on SRPC was reported by Kelkari and co-workers 229a
(Scheme 9.65). Working with carefully standardized reaction conditions