Soft and weak cooperation: Conformationallyflexible organic compounds were found to promote the title transformation. These “soft” organocatalysts, which are able to control processes through the differential activation entropies (ΔΔS≠S−R) of the reactive intermediates, lead to high stereoselectivities without the requirement of fine‐tuning the reaction temperatures (see scheme).
Stereoselective syntheses of N,N-bis(dihydrofuranyl)hydroxyamines from phenols and nitroolefins have been accomplished by means of cycle-specific catalysis with guanidine/bisthiourea organocatalyst and achiral base. Circumstantial evidence supports the idea that a nitroso intermediate participates in the dimerization, which involves internal redox reaction/umpolung.
Organocatalytic asymmetric conjugate addition of t-butyl nitroacetate to o-quinone methides: synthesis of optically active α-nitro-β,β-diaryl-propionates
作者:Ri-long Liu、Xiang-zheng Tang、Xue-jing Zhang、Ming Yan、Albert S. C. Chan
DOI:10.1039/c6ra28068d
日期:——
An asymmetric conjugate addition of t-butyl nitroacetate to in situ generated o-quinone methides had been developed. A chiral squamide derived from 9-amino-9-deoxyepiquinine was found to be the efficient catalyst. α-Nitro-β,β-diaryl-propionates could be obtained in good yields and with excellent enantioselectivities.