(Cyclobutenyl)carbene tungsten complexes are shown to
rearrange to 1-tungsta-1,3,5-hexatrienes. Azabicyclo[4.2.0]octadiene
(bis)carbene tungsten complexes
3a
−
c, which served
as model compounds in these studies, were generated by [4 + 2]- and
[2 + 2] domino
cycloaddition of 2 equiv of (1-alkynyl)carbene complex
(CO)5WC(OEt)C⋮CPh (1) to
alkenyl
imidates RCHCHC(OEt)NR1
(2a
−
c) (R = Ph, Me; R1
= Me, i-Pr). Compounds 3 are
stable in the solid state at 20 °C but rearrange in solution to
1-metalla-1,3,5-hexatrienes
7a
−
c by ring opening of the
cyclobutene ring and subsequent 1,3 hydrogen migration.
Compounds 3a and 7b were characterized by
crystal structure analyses.
Transannular O-heterocyclization is applied as a key step in a total synthesis. This highly stereoselective and metal-free transformation introduces four stereocenters in one step. It was chosen to be the pivotal step in the synthesis of Murisolin and 16,19-cis-Murisolin, two annonaceous acetogenins. The efficiency of this synthesis is further illustrated by a stereodivergent late-stage separation of both synthetic routes.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.