An
iron-catalyzed diastereoselective intermolecular olefin
amino-oxygenation reaction is reported, which proceeds via
an iron-nitrenoid generated by the N–O bond cleavage of a functionalized
hydroxylamine. In this reaction, a bench-stable hydroxylamine derivative
is used as the amination reagent and oxidant. This method tolerates
a range of synthetically valuable substrates that have been all incompatible
with existing amino-oxygenation methods. It can also provide amino
alcohol derivatives with regio- and stereochemical arrays complementary
to known amino-oxygenation methods.
Highly enantioselective chiral bifunctional thiourea catalyzed asymmetric tandem reactions for synthesis of substituted tetrahydroquinolines are described. Substituted tetrahydroquinolines were given in good yields (up to 98%), high enantioselectivities (up to >99% ee), and diastereoselectivities (up to 20:1 dr).
An enantioselective cascade Michael-Michael reaction between chalcones enolates and nitromethane catalyzed by a bifunctional thiourea is developed. This reaction provides a mild but efficient approach to chiral benzopyrans bearing three consecutive stereocenters in high yields with excellent stereoselectivities, and the benzopyrans can be easily transformed to the corresponding tricyclic product.
Cascading like dominos: An efficient and highly enantioselective synthesis of 2,3,4-trisubstituted tetrahydroquinolines through cascade aza-Michael-Michael reactions was developed. Tetrahydroquinolines were obtained in excellent yields, high enantioselectivities, and good diastereoselectivities, and could be easily transformed into ring-fused tetrahydroquinolines (see scheme).
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