Enantioselective cycloaddition of carbonyl ylides with arylallenes using Rh2(S-TCPTTL)4.

The first catalytic asymmetric carbonyl ylide cycloaddition with arylallenes is described. With dirhodium(II) tetrakis[N-tetrachlorophthaloyl-(S)-tert-leucinate], Rh2(S-TCPTTL)4, the cycloaddition of carbonyl ylides derived from diazoketoesters with arylallenes proceeded in a fully chemo- and regioselective manner to give highly functionalized 8-oxabicyclo[3.2.1]octanes with up to 99% ee and perfect exo diastereoselectivity.

Enantio- and diastereoselective hetero-Diels-Alder reactions between 2-aza-3-silyloxy-1,3-butadienes and aldehydes catalyzed by chiral dirhodium(II) carboxamidates.

The first catalytic asymmetric hetero-Diels-Alder reaction between 2-aza-3-silyloxy-1,3-butadienes and aldehydes is described. With dirhodium(II) tetrakis[N-benzene-fused-phthaloyl-(S)-piperidinonate], Rh(2)(S-BPTPI)(4), the cycloaddition reaction proceeded exclusively in an endo mode to give all-cis-substituted 1,3-oxazinan-4-ones in high yields with up to 98% ee.

Catalytic enantioselective intermolecular cycloaddition of diazodiketoester-derived carbonyl ylides with indoles using chiral dirhodium(II) carboxylates.

The first example of enantioselective intermolecular cycloaddition of carbonyl ylides with indoles is described. The cycloaddition of five- and six-membered carbonyl ylides derived from diazodiketoesters with N-methylindoles under catalysis by dirhodium(II) tetrakis[N-tetrachlorophthaloyl-(S)-tert-leucinate], Rh(2)(S-TCPTTL)(4), gave cycloadducts in high yields and with high levels of enantioselectivity (up to 99% ee) as well as excellent exo diastereoselectivity.

Multicomponent reactions involving tricyclooxonium ylide intermediate: diastereoselective synthesis of mono- and bisalkoxyoctahydro-1,4-benzodioxocin-6(5H)-one frameworks.

A highly diastereoselective tandem ring-enlargement and aldol condensation process involving multicomponent reactions of ethereal tricyclooxonium ylide intermediate with alcohols, mono- or dialdehydes in the presence of titanium(iv) isopropoxide is described to furnish alkoxyoctahydro-1,4-benzodioxocin-6(5H)-one ring systems.

Anomalous reaction of Rh2(OAc)4-generated transient carbonyl ylides: chemoselective synthesis of epoxy-bridged tetrahydropyranone, oxepanone, oxocinone, and oxoninone ring systems.

A series of symmetrical and unsymmetrical alpha,beta-unsaturated ketones such as arylmethylidenecycloalkanones (16, 19), bis(arylmethylidene)cycloalkanones (21, 23, 27), bisdiphenylnonatetraenones (30), and bis(phenylpropenylidene)cycloalkanones (33, 38, 42) were synthesized and subjected to the rhodium(II)-catalyzed tandem cyclization-cycloaddition reactions with various alpha-diazo ketones. These reactions afforded spiro epoxy-bridged tetrahydropyranone, spiro epoxy-bridged oxepanone (41, 43), epoxyoxocin-4(5H)-one (35, 37), and epoxyoxonin-5(6H)-one (40) frameworks starting from relatively simple precursors. The regio- and stereochemistry and solid-state architecture arrangements of several products were characterized by single-crystal X-ray structure analysis. The cycloaddition of carbonyl ylides with the compounds having both C=O and C=C groups was found to be chemo- and regioselective. Interestingly, an unusual ring enlargement of cycloadducts 34, 36, and 41 derived from C=O group addition was observed, affording epoxyoxocin-4(5H)-one and epoxyoxonin-5(6H)-one frameworks. Examples for the tandem cyclization-cycloaddition-ring enlargement reaction were also described. The rhodium(II)-generated carbonyl ylides behaved anomalously, furnishing the cycloadducts as a result of the cycloaddition of carbonyl ylides to C=O group despite the presence of C=C groups.

Highly regio- and chemoselective ring opening of oxa-bridged piperidinones toward functionalized furanones and piperidines.

Lewis acid mediated competitive ring-opening reactions of N-tosyl-substituted oxa-bridged piperidinone ring systems are demonstrated. A majority of the Lewis acids furnished the regio- and chemoselective reductive ring opening at the C(1)-N bond, whereas TiCl(4) furnished at the C(1)-O bond in the presence of triethylsilane, affording functionalized furanones and dihydroxypiperidines, respectively. [reaction: see text]

Highly regio-, chemo- and diastereoselective synthesis of oxa-bridged spirocycles: a novel observation of reverse selectivity.

The reverse regio- and diastereoselectivities are observed between the reactions involving 5- and 6-membered-ring cyclic carbonyl ylide dipoles with alpha-methylene ketones. A mild catalytic route to synthesize spirocyclic systems with high regio-, chemo- and diastereoselectivities is described.