Formaldehyde encapsulated in zeolite: a long-lived, highly activated one-carbon electrophile to carbonyl-ene reactions.

Gaseous formaldehyde is extremely unstable and readily undergoes self-polymerization to a solid paraformaldehyde or disproportionation to methanol and formic acid in the presence of moisture. We disclose a simple method to stably store such a labile formaldehyde as a monomer in a nanoporous faujasite zeolite at 5 degrees C for at least 50 days without self-polymerization or disproportionation. The greater stability of formaldehyde encapsulated in zeolite was confirmed by 13C MAS NMR spectroscopy. Formaldehyde was not only stabilized within the zeolite cages but functioned as a powerful electrophile toward various olefins. Zeolite-encapsulated formaldehyde was proved to be a stable but highly reactive C1 reagent.

Catalytic enantioselective epoxidation of homoallylic alcohols by chiral zirconium complexes.

Catalytic enantioselective epoxidation of homoallylic alcohols using Zr(Ot-Bu)(4) and tartrate ester (or tartramide) has been developed. In the Zr(Ot-Bu)(4)/diisopropyl tartrate-catalyzed epoxidation, the reverse of the enantiofacial preference was observed, depending on the Zr/ligand ratios of 1:1 or 1:2. [reaction--see text]

Practical carbonyl-ene reactions of alpha-methylstyrenes with paraformaldehyde promoted by a combined system of boron trifluoride and molecular sieves 4A.

[reaction: see text] A combined system of boron trifluoride and molecular sieves is an efficient promoter for the carbonyl-ene reaction of alpha-methylsyrenes with paraformaldehyde. The coexistence of BF3 x OEt2 and molecular sieves 4A is essential for obtaining high yields of ene products.