Organotransition metal-modified sugars: Part 16. Diastereoselective synthesis of carbohydrate-derived spirocyclic 2-oxacyclohexylidene chromium and tungsten complexes

Carbohydrate-derived 4-pentyn-1-ols have been synthesized from spirocyclic oxirane precursors upon reaction with allenylmagnesium bromide. They undergo cycloisomerization at low-valent chromium or tungsten templates to give spirocyclic 2-oxacyclohexylidene metal complexes.