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OMe
N
P(
t
Bu)
2
P(
t
Bu)
2
N
MeO
PR
2
P(
t
Bu)
2
Ph
Ph
i
Pr
i
Pr
Me
2
N
PCy
2
Fe
N
N
Ph
L2
(BippyPhos)
L3
(
t
BuDavePhos)
L1
(JosiPhos; CyPF-
t
Bu)
i
Pr
L4
, R = Cy
(BrettPhos)
L5
, R = 1-Ad
(AdBrettPhos)
(OMe)
Ph
PR
2
Me
N
(Me)
MeO
Me
Ph
P(
t
Bu)
2
N
N
O
Me
PR
2
L10
, R = 1-Ad
(Mor-DalPhos)
L11
, R = 2-tolyl
i
Pr
i
Pr
PPh
2
L8
i
Pr
OMe
O
P(1-Ad)
2
L6
, R = Cy
(Me
3
(OMe)XPhos)
L7
PCy
2
PPh
2
, R = Ph
(Me
3
(OMe)PhXPhos)
NMe
2
L9
(Me-DalPhos)
NMePh
L12
(Zheda-Phos)
L13
(XantPhos)
Figure 5.2
Structures of the ancillary ligands discussed in this chapter.
challenging reaction partners, given the broad synthetic potential of these
novel transformations in chemical synthesis. For convenience, structural
drawings of the ancillary ligands featured here, along with their common
names where available, are presented in Figure 5.2.
5.2 Selective Monoarylation of Ammonia
Substituted primary anilines and related heteroaromatics represent com-
mon molecular fragments in biologically active compounds and can also
serve as synthons in the rational construction of unsymmetrical secondary
and tertiary arylamines. In consideration of the aforementioned synthetic
limitations associated with nitration-reduction reaction sequences and
nucleophilic aromatic substitutions en route to anilines, as outlined in
Section 5.1, it is perhaps not surprising that the pursuit of BHA protocols for
the construction of primary (hetero)arylamines has attracted considerable
attention. Whereas the use of protected 'ammonia equivalents'
26
has been
applied successfully in BHA chemistry, the direct and more atom-
economical use of ammonia itself in the assembly of primary (hetero)-
arylamines has proven to be particularly problematic. Indeed, many
metal-catalyzed chemical transformations, including BHA, that are well
established for other amine classes do not proceed with useful eciency and
selectivity when employing ammonia as a substrate using commonly
employed reaction conditions.
27-29
Diculties associated with the use of
ammonia in BHA chemistry include, but are not restricted to: deactivation of
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