Easy access to trans-2,3-disubstituted cyclobutanones, 2,4,5-trisubstituted 3,6-dihydro-2H-pyrans and cis-substituted phenylcyclopropylsulfones by using the highly versatile 1-phenylsulfenyl- or 1-phenylsulfonyl-cyclopropylketones.

The high versatility of 1-phenylsulfenyl- or 1-phenylsulfonyl-cyclopropylketones has been exploited for the regioselective synthesis of trans-2,3-disubstituted cyclobutanones, 2,4,5-trisubstituted 3,6-dihydro-2H-pyrans and cis-2-alkyl- or cis-2-aryl-cyclopropylphenylsulfones.

l-Proline-catalyzed direct intermolecular asymmetric aldol reactions of 1-phenylthiocycloalkyl carboxaldehydes with ketones. Easy access to spiro- and fused-cyclobutyl tetrahydrofurans and cyclopentanones.

[reaction: see text] Acid-catalyzed ring expansion of chiral cyclopropyl and cyclobutyl derivatives for the synthesis of carbo- and heterocyclic compounds is reported. The starting materials have been successfully prepared by l-proline-catalyzed direct asymmetric aldol reactions of 1-phenylthiocycloalkyl carboxaldehydes with ketones.

Regioselective synthesis of trisubstituted 2,3-dihydrofurans from donor-acceptor cyclopropanes or from reaction of the Corey ylide with alpha-sulfenyl-, alpha-sulfinyl-, or alpha-sulfonylenones.

[reactions: see text] Regioselective synthesis of 2,4,5- or 3,4,5-trisubstituted 2,3-dihydrofurans has been realized by using donor-acceptor cyclopropanes or by a Corey ylide reaction with alpha-sulfenyl-, alpha-sulfinyl-, or alpha-sulfonylenones. The method allowed a straightforward synthesis of the natural product calyxolane B.

2,2-dimethyl cyclopentanones by acid catalyzed ring expansion of isopropenylcyclobutanols. A short synthesis of (+/-)-alpha-cuparenone and (+/-)-herbertene.

2,2-dimethyl cyclopentanones are readily prepared by acid catalyzed ring expansion of isopropenylcyclobutanols; the method allows ready access to the family of sesquiterpenes cuparanes and herbertanes, as demonstrated by the synthesis of (+/-)-alpha-cuparenone and the direct precursor of (+/-)-herbertene.

Unexpected stereochemistry in the lithium salt catalyzed ring expansion of nonracemic oxaspiropentanes. formal syntheses of (-)-(4R,5R)-muricatacin and the pheromone (R)-japonilure.

[reaction: see text] The stereochemistry of the cyclobutanones 3, obtained by lithium salt catalyzed ring expansion of the optically pure oxaspiropentanes 2, depends not only on the lithium salt but also on the stereochemistry of 2. They constitute the starting material for the syntheses of the acetogenin (-)-(4R,5R)-muricatacin and the pheromone (R)-japonilure.

Synthesis of new heterocycles through a cation-driven tandem ring-enlargement-annulation reaction.

[reaction: see text] The thionium ion, generated through a cyclopropylcarbinyl-cyclobutyl ring expansion, is, for the first time, intramolecularly intercepted by activated aromatic rings to generate new versatile 2a-methyl-8b-(phenylsulfanyl-1,2a,3,8b-tetrahydro-2H-cyclobuta[c]chromenes.