An enantioselective tandem Michael addition/cyclization reaction between trisubstituted 2‐nitro‐1,3‐enynes and cyclic 1,3‐diketones catalyzed by a chiral organosquaramide catalyst in the presence of Ag2CO3 was developed. The chiral functionalized chromene products could be obtained in good yield and in 80–99% enantiomeric excess. The structures and absolute configurations of some of the products were confirmed by X‐ray crystallographic analysis.magnified image

Reported herein is the construction of chiral aza‐[n.2.1] skeletons by separable epimers of intramolecular [3+2] cross cycloaddition of cyclopropane 1,1‐diesters with chiral sulfinylimines. The epimer products can be separated by silica gel column chromatography.

A Lewis acid promoted tandem reaction of intramolecular [3 + 2] cycloaddition/OÀ H insertion/ester exchange of cyclopropanes with diazocarbonyls is reported to synthesize fused-oxa-[n.2.1] skeletons, which tolerates both aryl and alkyl diazocarbonyl substrates. A wide variety of fused-oxa-[n.2.1] skeletons were efficiently constructed.

The asymmetric synthesis of Szántay's amine (+)-2, the pivotal precursor for direct access to (+)-cycloclavine (1), is described for the first time in eleven steps with 19.7% overall yield from the commercially available 4-bromoindole. The strategy features an asymmetric induction by Ellman's sulfinimine and rhodium-catalysed isomerization of the C[double bond, length as m-dash]C bond.