Rhodium-Catalyzed Stereoselective Intramolecular Tandem Reaction of Vinyloxiranes with Alkynes: Atom- and Step-Economical Synthesis of Multifunctional Mono‑, Bi‑, and Tricyclic Compounds

Skeletal
diversity in diversity-oriented synthesis has proven to
be especially challenging. A rhodium-catalyzed intramolecular tandem
reaction of vinyloxirane-alkynes leading to four structurally distinct
classes of mono-, bi-, and tricyclic carbocycles and heterocycles
was developed. [Rh­(NBD)2]+BF4– is identified to be an efficient catalyst for these
transformations. Using this highly efficient catalyst, hetero-[5 +
2] cycloadditions, tandem hetero-[5 + 2] cycloaddition/Claisen rearrangements,
and subsequent cyclopropane ring-opening reactions of vinyloxiranes
with monoalkynes afford 2,5-dihydrooxepins, tetrasubstituted vinylcyclopropanes,
and multifunctional five-membered rings, respectively, under mild
conditions with high stereoselectivity and yield. Moreover, hetero-[5
+ 2] cycloaddition/Claisen rearrangement/[5 + 2] cycloaddition reactions
of vinyloxiranes with diynes for step-economical construction of linearly
fused 5-7-5 tricyclic skeletons has also been developed. The complete
transfer of chirality from readily available vinyloxiranes to the
corresponding products provides a highly efficient and practical access
to these chiral cyclic compounds.