Handbook of Functionalized Organometallics Applications in S

Cbz
72
N
H
3 Functionalized Organoborane Derivatives in Organic Synthesis
Guy has explored copper-mediated S-arylation of thiols and aryl boronic
acids [67]. Earlier studies revealed that the reactions were slow for S-arylation
under the conditions developed previously for N- and O-arylation reactions
because of a significant disulfide formation. However, it was shown later that the
reaction of a wide range of electronically diverse aryl boronic acids with a range of
thiolate substrates proceeded well when heated at 155 C in DMF affording crosscoupled
products in good yields. Similarly cysteine phenyl sulfide 103 and an
arylthio glycoside 104 were also prepared in 50±80% yields (Scheme 3.46).
SH
SH
O
O
(HO) 2B
R
Cu(OAc) 2 (1.5 equiv)
pyridine, 4 Å MS
2 equiv
DMF, reflux
Cu(OAc) 2 (1.5 equiv)
PhB(OH) 2 (2 equiv)
pyridine, 4 Å MS
DMF, reflux
Cbz
N
H
S
O
103: 79 %
Scheme 3.46 Copper-mediated thioether synthesis.
O
S
65 - 88 %
AcO
S
R
OAc
OAc
O
104: 51 %
A new synthesis of thioethers involving copper-catalyzed cross-coupling of aryl
boronic acids with N-aryl/heteroaryl thiosuccinmides has been described by Liebeskind
and coworkers [68]. The reaction proceeds in the absence of base under
mild conditions utilizing various aryl boronic acids. S-arylation is now possible for
the first time under nonbasic conditions (Scheme 3.47).
O
RS N
ArB(OH) 2
CO2Cu OH
(20-30 mol %)
THF, 45-50 ºC
O
Scheme 3.47 Copper-catalyzed cross-couplingof organothiolimides
with boronic acids.
RS-Ar
51 - 83 %
OAc