Divergent Stereoselectivity in Phosphothreonine (pThr)-Catalyzed Reductive Aminations of 3-Amidocyclohexanones
摘要:
Phosphothreonine (pThr)-embedded peptide catalysts are found to mediate the reductive amination of 3-amidocyclohexanones with divergent selectivity. The choice of peptide sequence can be used to alter the diastereoselectivity to favor either the cis-product or trans-product, which are obtained in up to 93:7 er. NMR studies and DFT calculations are reported and indicate that both pathways rely on secondary interactions between substrate and catalyst to achieve selectivity. Furthermore, catalysts appear to accomplish a parallel kinetic resolution of the substrates. The facility for phosphopeptides to tune reactivity and access multiple products in reductive aminations may translate to the diversification of complex substrates, such as natural products, at numerous reactive sites.
A new strategy for the aza-Michael reaction of amides and ureas with α,β-unsaturated enones, which uses p-TsOH·H2O as an efficient and inexpensive catalyst under high-pressure conditions, has been developed.
carbon-containing nucleophiles to cyclicenones. Using this conjugate addition reaction, a variety of different nucleophiles can react with a range of cyclicenones in the presence of p-toluenesulfonic acid under solvent-free ultrasound irradiation conditions affording the corresponding C–N or C–C adducts in good to excellent yields. Comparatively, performing the reaction under ultrasound irradiation gives