Asymmetric Cyclization/Nucleophilic Tandem Reaction of o-Alkynylacetophenone with (Diazomethyl)phosphonate for the Synthesis of Functional Isochromenes.

An efficient asymmetric reaction between (diazomethyl)phosphonate with o-alkynylacetophenone has been established by employing different stereocontrol strategy. A variety of isochromenes bearing tetrasubstituted stereocenters and (diazomethyl)phosphonate at the 1-position were prepared in yield up to 99% with enantioselectivity up to 94% enantiomeric excess (ee) for the first time. These functional isochromenes could be transformed to important structural motifs in biologically active compounds. Moreover, density functional theory calculations were conducted to gain insight into the process and the stereoselectivity.