A novel approach to bicyclic fused cyclopentenone derivatives

A new four-step reaction sequence leading to bicyclic fused cyclopentenone derivatives starting from cyclic ketones has been developed.     

Facile beta-alkyl and beta-hydride elimination in the nickel-catalyzed annulation of o-iodophenyl ketones and aldehydes with bicyclic alkenes

[reaction: see text] o-Iodoaryl aldehydes react with bicyclic alkenes in the presence of NiBr(2)(dppe) and Zn powder in acetonitrile at 80 degrees C undergoing annulation to give polycyclic ketone derivatives. Surprisingly, o-iodoaryl alkyl ketones also react with bicyclic alkenes to form polycyclic ketones with structures the same as those from the corresponding o-iodoaryl aldehydes.     

Intramolecular sulfur-ylide additions to ketones. A cyclopentane annulation1

Various 2-(3′-phenylthiopropyl)cycloalkanones were prepared from the corresponding cyclic ketones and subjected to S-alkylation by triethyloxonium tetrafluoroborate followed by potassium $\text{tert}$-butoxide treatment to give bicyclic epoxides with new five-membered carbocycles. A related cyclization to a six-membered ring was also observed.     

Synthesis of new bicyclic compounds containing fused sulfolane and pyrazolidine rings

3-Aryl-6а-methyl-6-nitro-1-carbamoylhexahydrothieno[2,3-d]pyrazole-4,4-dioxides, novel original bicyclic species consisting of fused pyrazolidine and sulfolane rings, and 1,4-adducts were obtained by reacting 2-benzylidene-3-methyl-4-nitro-3-thiolene-1,1-dioxide and its derivatives with semicarbazide.     

Kinetics of the cis,cis to trans,trans isomerization of 1,1,2,2,5,5,6,6-octamethyl-1,2,5,6-tetrasilacycloocta-3,7-diene

The kinetics of the ruthenium-promoted cis,cis to trans,trans isomerization of 1,1,2,2,5,5,6,6-octamethyl-1,2,5,6-tetrasilacycloocta-3,7-diene were investigated. Incubation of a ruthenium alkylidene complex, (Cy(3)P)RuCl(2)(==CHPh)Ru(p-cymene)Cl(2), in CD(2)Cl(2) for 5 days at 40 degrees C afforded a catalytically active ruthenium species that was shown to be responsible for promoting the isomerization. The isomerization was observed to proceed in two steps: (1) conversion of the starting cis,cis isomer to a proposed cis,trans intermediate and (2) subsequent conversion of the intermediate to the product trans,trans isomer. Kinetic studies demonstrated that the two steps are first-order with respect to the concentrations of the cis,cis isomer, the intermediate, and the ruthenium alkylidene complex. The data were further consistent with a mechanism involving bimolecular hydride addition-elimination during the two isomerization steps.     

A Diastereoselective Synthesis of trans/cis Octahydronaphthoquinolizine

The tetracyclic system of 2,3,6,7,7a,8,12b,12c-octahydro-lH,5H-naphtho[1,2,3,i,j]quinolizine with trans/cis fusions of the B/D and B/C rings has been diastereospecifically synthesized in nine steps and in 23% total yield.     

Diastereoselective cis to trans desymmetrization of dimethyl succinates

Meso-succinates, readily available by Diels–Alder cycloaddition of dimethyl maleate or maleic anhydride followed by esterification, can be isomerized quantitatively from the cis to the trans isomers in the presence of lithium alkoxides. The reaction performed with enantiopure chiral lithium alkoxides yields diastereomeric trans-succinates in good yield and selectivity.     

Synthesis of fused bicyclic glutarimides

We describe an efficient route towards the synthesis of fused bicyclic glutarimides using facile [3+3] reaction of α-sulfonylacetamides with different α,β-unsaturated esters as the key step. Intramolecular cyclization of 4-substituted 3-sulfonylglutarimide to form 5,6-, 6,6- or 6,7-fused bicyclic glutarimides was accomplished via alkylation, oxidative cyclization or ring-closing metathesis in modest yield.     

A new stereospecific annulation

A new, high yield, two-step annulation method has been developed which features stereospecific formation of three contiguous asymmetric centers.     

Synthesis of new chiral N-substituted fused pyrazoles and pyrazolinols

Treatment of β-diketones and the corresponding β-enaminoketones, having modified carane (2-ethyl-6,6-dimethylbicyclo[3.1.0]hexane) and p-menthane (3-ethyl-1-isopropylcyclopentane) skeletons, with aryl- and alkylhydrazines results in regioselective formation of N-substituted pyrazoles or stable pyrazolinols depending on the nature of the substituent at the hydrazine nitrogen.     

A convenient synthesis of cis and trans 4-tert-butoxycarbonyl-substituted cyclohexylglycine

A novel synthesis of cis and trans substituted 4-tert-butoxycarbonyl cyclohexylglycines via asymmetric aminohydroxylation of vinyl styrene followed by reduction of the aromatic ring and subsequent oxidation is reported.     

Synthesis and reactivity of new chiral bicyclic phospholanes as acyl-transfer catalysts

[structure: see text] Synthesis of chiral phosphines 1a, 14a, and 18a as nucleophilic catalysts for anhydride activation and kinetic resolution of alcohols is described. Radical cyclization of alkenylphosphines produced the phosphabicyclooctane (PBO) core of catalysts 1a and 14a, while 18a was made by quenching a metallocycle precursor with dichlorophenylphosphine. Catalysts 1a and 14a are less reactive, while 18a is comparable to the most reactive catalysts in the PBO family. The preferred ground-state geometries of phosphine-boranes were identified using computational methods, and were correlated with the catalytic reactivity of the corresponding free phosphines.     

Vinylsilane mediated regiospecific cyclopentenone annulation of ketones

The development of a new cyclopentenone annulation sequence of general scope which involves Friedel-Crafts acylation of a vinylsilane with an α,β-unsaturated acid chloride followed by Nazarov cyclization is reported.     

Mass spectra of bicyclic terpenoid ketones

Examination of fragmentation patterns of five bicyclic ketones containing cyclopropane rings and their deuterated analogs indicates that similarity in structure gives minimal similarity in fragmentation. No generalizations can be made concerning either the loss of similar fragments or their deuterium content.     

Aromatic annulation on the p-menthane monoterpenes: enantiospecific synthesis of the trans and cis isomers of calamenene and 8-hydroxycalamenene

A new enantiospecific route to sesquiterpenes of the calamenene family is described. The synthetic pathway starts from easily available 3-oxygenated-p-menthane monoterpenes and affords the title compounds by a homologation-benzannulation sequence. The trans and cis isomers of the natural compounds calamenene and 8-hydroxycalamenene were obtained in enantiopure form starting from (−)-menthone and (+)-isomenthone, respectively.