N-(Aryloxy)imines, readily accessible by condensation/tautomerization
of (pseudo)benzylic primary amines and 2,6-di-tert-butyl-1,4-benzoquinone, undergo efficient allylation to afford a
wide range of homoallylic primary amines following hydrolytic workup.
Deprotonation of N-(aryloxy)imines generates a delocalized
2-azaallyl anion-type nucleophile that engages in dearomative C–C
bond-forming reactions with allylpalladium(II) electrophiles generated
from allylic tert-butyl carbonates. This reactivity
umpolung enables the formal α-allylation of (pseudo)benzylic
primary amines. Mechanistic studies reveal that the apparent regioselectivity
of the desired bond-forming event is a convergent process that is
initiated by unselective allylation of N-(aryloxy)imines
to give several regioisomeric species, which subsequently rearrange
via stepwise [1,3]- or concerted [3,3]-sigmatropic shifts, ultimately
converging to provide the desired regioisomer of the amine products.
A new method for imine synthesis by way of quinone-catalyzed oxidative deformylation of 1,2-amino alcohols is reported. A wide range of readily accessible amino alcohols and primary amines can be reacted to provide N-protected imine products. The methodology presented provides a novel organocatalytic approach for imine synthesis and demonstrates the synthetic versatility of quinone-catalyzed oxidative C–C bond cleavage.
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