PdII-promoted [2 + 3] cycloaddition of pyrroline N-oxide to organonitriles. Application of (Δ4-1,2,4-oxadiazoline)-PdII complexes in the Suzuki–Miyaura reaction †
Abstract
[2 + 3] Cycloaddition reactions of the organonitriles RCN 1 (R = Me (1a), Et (1b), p-IC6H4 (1c), p-BrC6H4 (1d), p-ClC6H4 (1e), p-FC6H4 (1f)) with the pyrroline N-oxide−O+N
CHCH2CH2C
Me22 in the presence of PdCl2 proceed at room temperature for 12 h and allow the isolation of the corresponding palladium(II) complexes trans-[PdCl2{
N
C(R)O
NC
(H)CH2CH2C
Me2}2] 3a–3f containing fused bicyclic Δ4-1,2,4-oxadiazoline
N
C(R)O
NC
(H)CH2CH2C
Me2 (R = Et (4b), p-FC6H4 (4f)) are liberated upon reaction of complexes 3b,3f with a diphosphine (
N
C(NHCOC6H4F-4)CH2CH2C
Me2}2] 5 was formed in a minor amount upon N–O bond cleavage of the oxadiazoline ring to give a pyrrolylbenzamide species coordinated by the N-atom of the