144
4.4.4.2 Oxidative C(sp2)-P Bond Formation
Radical oxidative C-P coupling between simple arenes and diethyl phosphite promoted by a AgNO 3 /Na 2 S 2 O 8 co-catalyst system is reported as the first example
(Scheme 4.66) [50]. However, this transformation exhibits low regioselectivity, and
the wide application is limited.
Phosphonation of arenes bearing electron-withdrawing directing groups with
diethyl phosphite using Ag 2 SO 4 as catalyst and K 2 S 2 O 8 as oxidant is developed
(Scheme  4.67) [51]. And 2-phosphonation of arenes can be achieved due to the
directing groups. N,N-dialkylbenzamides, N,N-dialkylbenzenesulfonamides, and
nitrobenzene are suitable substrates. A radical mechanism is also proposed for this
transformation. Phosphoryl radical is involved as the key intermediate in this radical
process.
Ar
R
N
AcO
O
HP
1) CuCl, PCy 3 , Ac 2 O
dioxane, 130 °C, N 2
2) HCl aq.
Ph
Ph
+
Ar
R
O
P
O
Ph
Ph
O
P
O
Ph
Ph
74%
O
P
O
Ph
Ph
76%
O
P
O
Ph
Ph
66%
MeO
O
P
O
Ph
Ph
71%
OMe
O
P
O
Ph
Ph
71%
O
P
O
Ph
Ph
62%
Ar
R
N
AcO
O
HP
CuCl, PCy 3 , Ac 2 O
Ph
Ph
+
Ar
R
NH
P
O
Ph
Ph
Ar
R
NH
O
P Ph
Ph
Cu(I)
Cu(II)
+
radical coupling
Ar
R
NH
P
O
Ph
Ph
Ac 2 O
Scheme 4.65 a-Phosphorylation of aryl ketones
W. Liu