ring could also be obtained using this method (Scheme 30) [62]. Further
investigations revealed that the straight intramolecular coupling of amino group
and aryl halides could be affected by using different combination of Pd 2 (dba) 3
(or Pd(OAc) 2 ) with P(2-furyl) 3 , P(o-tolyl) 3 , DPEphos, MOP, Xantphos or BINAP
to give the corresponding indolines and other N-containing heterocycles 85 [63].
Using the same strategy, Houghten et al. developed a solid-phase synthesis
for indolines (Scheme 31) [64]. When enantiopure amines were used, cyclization
conditions did not lead to the racemization of the products.
Dineen and Michaelis reported a new method for synthesizing 2-substituted
indolines. They prepared the amination substrates 90 via ring opening of aziridines
with o-bromophenyl metal reagents, which were subjected to Pd(OAc) 2 /DPEPhos-catalyzed intramolecular amination to afford enantiopure indolines 91
(Scheme 32) [65].
Scheme 30 Pd-catalyzed synthesis of indolines and related heterocycles
Scheme 31 Solid-phase synthesis of indolines via Pd-catalyzed intramolecular C–N bond formation
Scheme 32 Synthesis of 2-substituted indolines via ring opening of aziridines and subsequent
Pd-catalyzed intramolecular amination
100
Y. Jiang and D. Ma