296
well applicable for the rapid synthesis of various heterocycles under optimized reaction conditions. Ellman et  al. demonstrated the rhodium-catalysed arylation of
azoles and aryl halides through C–H bond activation under microwave irradiation
(Scheme 79) [270]. This method reported the tolerance of wide substrate scope and
application of microwave radiation in this reaction led to the reduced reaction time.
Jun et al. reported the microwave-assisted Rh-catalysed N-annulation of ketones
and alkynes (Scheme 80) [271]. This method afforded the quick synthesis of a wide
array of isoquinoline and pyridine compounds in high yields under microwave irradiation. Four-component N-annulation reactions of alkyne with cycloalkanones was
also presented to construct tetrahydroquinoline moiety. Recently, Van der Eycken
et al. reported the microwave-assisted rhodium(III)-catalysed intramolecular annulation to develop the synthesis of the indolizinone and quinolizinone moieties
(Scheme 81) [272]. Microwave-assisted annulation via C(sp
2
)–H activation combined with Ugi reaction demonstrated as the rapid approach for diversification of
peptidomimetics and oligopeptides.
O
N
H
R 2
RuCl 2( p-cymene) 2 (10 mol%)
Cu(OAc)2 (50 mol%)
t-AmOH (1.5 mL)
MW, 120
o C, 1h
R 2
Ph
Ph
N
O
Ph
Ph
R 1
R 1
Scheme 77 Ru-catalyzed ortho-C–H activation for synthesis of substituted isoquinolines
Condition A
RhCl( PPh 3)3 (10 mol%)
250
o C, 20 min
Condition B
RhCl( coe )2 2 (2.5 -5 mol%)
HClPCy3 (5-10 mol%)
225-250
o C, 6-12 min
N
N
R 1
R 3
R 2
N
N
N
N
R 1
R 2
R 3
R 1
R 2
R 3
( )n
( )n
( )n
Scheme 78 Rh-catalysed intramolecular coupling of a benzimidazole C–H bond
RhCl( coe )2 2 (0.05 equiv)
Lig a, b (0.3 equiv)
N
H
N
Br
R
N
H
N
R
P
Cy
P
Cy
Lig a, b
DCB, iPr 2 iBuN (3 equiv)
microwave ( 250
o C), 40 min
Scheme 79 Rh-catalysed C–H arylation of azoles and aryl halides
D. S. Deshmukh et al.