Palladium-catalyzed cyclization reactions of 3-propargylthio 1,2,4-triazin-5(2h)-ones to thiazolo-1,2,4-triazinones

Selective transformation of 3-propargylthio-1,2,4-triazin-5(2H)-ones ($\text{1}$) to 6-methylene-6,7-dihydro-4H-thiazolo[2,3-c][1,2,4]-triazin-4-ones ($\text{2}$) and 3-methylene-2,3-dihydro-7H-thiazolo[3,2-b]-[1,2,4]triazin-7-ones ($\text{3}$) is performed under the conditions of Pd(II) salt or sodium hydroxide catalysis, respectively.     

Valence isomerization of C9H10hydrocarbons: Photochemical reactions of bicyclo [3.2.2] nona-2,6,8-triene and its dihydro-derivatives

The valence isomerization reaction of bicyclo[3.2.2]nona-2,6,8-triene ($\text{2}$), which photoisomerized to two homologues of semibullvalene, was discussed with the photoreactions of its dihydro-dreivatives, bicyclo[3.2.2]nona-6,8-diene ($\text{3}$) and bicyclo[3.2.2]nona-2,6-diene ($\text{4}$).     

Formation and trapping of 6-azabicyclo[3.2.2]non-5-ene,a strained bridgehead imine

Photolysis or flash vacuum pyrolysis of 1-bicyclo[3.2.1]octylazide $\text{9}$ yields 6-azabicyclo[3.2.2]non-5-ene $\text{10}$, a strained bridgehead imine, which could not be isolated but was trapped with methanol.     

Synthesis of (1s,5r)-karahana ether and (1s,5r)-karahana lactone,the optically active forms of unique monoterpenes wit

(1$\text{S}$,5$\text{R}$)-(-)-Karahana ether (8,8-dimethyl-2-methylene-6-oxabi-cyclo[ 3.2.1]octane) and (1$\text{S}$,5$\text{R}$)-(-)-karahana lactone (8,8-dimethyl-2-methylene-6-oxabicyclo [3.2.1]octan-7-one) were synthesized from ($\text{S}$)-3-hydroxy-2,2-dimethylcyclo-hexanone. The natural karahana lactone was shown to be almost racemic ($\text{ca}$. 1.3 % e.e.).     

1,2-Dialkoxycarbonylhydrazine derivatives of pyrroles and indolizines. A new synthesis of cycl[3.2.2]azines

The reaction of pyrroles $\text{1}$ with diisopropyl azodicarboxylate $\text{2}$ yields 2- and 2,5-substituted derivatives. 3- and 1,3-substituted indolizines $\text{5}$ and $\text{6}$ are formed by the same route. Cycl[3.2.2]azines $\text{7}$ have been obtained from $\text{5}$ and $\text{6}$ with dimethyl acetylenedicarboxylate.     

Conversion directe des phospholes en dihydro-6,7 phosphepines dans la sphere de coordination du tungstene

In the presence of AlCl₃, [1-β-chloroethyl-3,4-dimethylphosphole]pentacarbonyltungsten($\text{1}$) rearranges into [1-chloro-3,4-dimethyl-6,7-dihydrophosphepin]pentacarbonyltungsten ($\text{3}$).     

Nitrogen bridgehead compounds. Part 60. Unusual amination with sodium azide.

9-Bromo-6,7,8,9-tetrahydro-4$\text{H}$-pyrido [1,2-$\text{a}$]pyrimidin-4-ones react with sodium azide to afford 9-amino-6,7-dihydroanalogues. A mechanism involving a tricyclic tetrazine intermediate formed by neighbouring-group participation is suggested.     

Sigmatropic 1.5-hydrogen shift and concomitant cyclopropane bond cleavage on thermolysis of trans-1-isopropenyl-4-methylene spiro[2.x]alkanes into 1-methylene-(3′-methylbut-2′-enyl)-cycloalk-2-enes

Thermolysis of several trans-1-isopropenyl-4-methylene-spiro[2.x]- alkanes (x = 4,5) in xylene solution at 130° causes quantitative rearrangement to 1-methylene-2-(3′-methylbut-2′-enyl)cycloalkanes ($\text{3}$ – $\text{4}$).     

A novel route to bicyclic iron tricarbonyl complexes involving π-allyl and σ-components

Nucleophilic attack of CN⁻ on bicyclo[3.2.1]octadienyl-, bicyclo[3.2.2]- nonadienyl-, and 6,7-benzobicyclo[3.2.2]nonadienyliron tricarbonyl tetrafluoroborates, results in mixed-type complexes containing both σ and π-allyl bonds. The cyano group in the products is located exo to the bicyclic ring.In contrast, the three cations react smoothly with I⁻; carbon monoxide is displaced to give iron complexes containing covalently-bound halogen.     

The synthesis of barbaralyl systems via bicyclic[3.2.2] irontricarbonyl cations

Reaction of bicyclo[3.2.2] tertiary alcohols 7b,c and 23b with Fe₂(CO)⁹, resulted in the corresponding dienyl Fe(CO)₃ complexes, which upon HBF₄/Ac₂O treatment yielded the bicyclo [3.2.2] dienyl irontricarbonyl cations. Nucleophilic addition of CN^- to those cations, resulted in the formation of δ,μ-bonded complexes, which were degraded with Me₃NO to give substituted tricydic hydrocarbons (barbaralyl systems) in unusual positions. For purpose of comparison, the trifluoroacetolysis of 2-methyl-endo-6,7-benzobicyclo[3.2.2] nonatriene (22) has been studied.     

Photooxygenation of bicyclopropylidene

Upon photooxidation bicyclopropylidene ($\text{1}$) yields spiro[2.3]hexan-4-one ($\text{4}$) and 7-oxatrispiro[2.0.2.1]heptane ($\text{6}$). The formation of these is rationalized. Authentic $\text{6}$ was prepared by epoxidation of $\text{1}$, and $\text{4}$ by isomerization of $\text{6}$.     

Comparison of cationic rhodium and iridium complexes in directed homogeneous hydrogenation

The hydrogenation of $\text{endo}$-6-methylenebicyclo[2,2,2]octan-2-ol catalysed by a range of rhodium and iridium complexes has been investigated. Unlike the corresponding $\text{exo}$-alcohol, reduction is highly stereoselective leading to 95 – 99.7% of $\text{endo}$-exo-6-methylbicyclo[2,2,2]octan-2-ol. Selectivity is much less pronounced for the corresponding methyl ether. Rhodium catalysts promote a competitive isomerisation of the double bond to $\text{endo}$-6-methyl-bicyclo[2,2,2]oct-5-en-2-ol, of which an authentic sample was reduced in high yield to pure $\text{exo}$-$\text{endo}$ product. Reduction of both $\text{endo}$-hydroxy substrates by iridium complexes is rapid and highly selective.NMR studies employing europium shift reagents played a central part in defining the stereochemical interrelationships of 2,6-disubstituted bicyclo[2,2,2]octanes.     

Condensed cyclic and bridged-ring systems : part 12: A novel synthetic route to 4-p-methoxyphenyl-bicyclo[ 2.2.2 ]octan-2-ones and some bicyclo [ 3.2.1 ] octane derivatives by acid-catalyzed intramolecula

The efficacy of a new acid-catalyzed intramolecular C-alkylation has been demonstrated by the synthesis of 1-methyl-4-$\text{p}$-methoxyphenylbicyclo [2.2.2] octan-2-one ($\text{5}$) and 4-$\text{p}$-methoxyphenylbicyclo [2.2.2] octan-2-one ($\text{6}$) from easily accessible starting materials. The carbinol $\text{20}$, derived from $\text{5}$, undergoes facile rearrangement leading to 1-$\text{p}$-methoxyphenyl-4-methyl bicyclo [3.2.1] oct-3-ene ($\text{22}$), which has been transformed to $\text{endo}$-1-$\text{p}$-methoxyphenyl-4-methylbicyclo [3.2.1] octan-3-one ($\text{25}$).     

Novel photoisomerization of 5-chloro-1,4-dihydro-9-methyl-naphthalen-1,4-imine

Direct photolysis of 5-chloro-1,4-dihydro-9-methyl-naphthalen-1,4-imine in cyclohexane gave a mixture of 1-chloronaphthalene and isomeric dihydrocyclobut[b]indoles $\text{5}$ and $\text{6}$. Dihydrocyclobut[b]indoles $\text{5}$ and $\text{6}$ thermally rearranged to give 1-benzazepines $\text{7}$ and $\text{8}$, respectively.     

Erzeugung und cycloaddition von allyliumionen aus α-halogenketonen unter solvolyse-bedingungen

Some α-haloketones react with furan in methanolic solution in the presence of base to form the 3-oxo-8-oxabicyclo[3.2.1]oct-6-enes ($\text{11}$), the products derived from a [4+3] cycloaddition of an allylium intermediate ($\text{5}$ or $\text{6}$).     

A novel approach to complex terpenoid methylenecyclohexanes

Allylic alcohols $\text{3}$ and $\text{4}$ have been prepared and activated toward formation of allyl cations, giving 3-methylenebicyclo [3.2.1] oct-6-enes $\text{7}$ and $\text{9}$, respectively, in the presence of cyclopentadiene; with furan, not only the products of conventional eletrophilic substitution $\text{11}$ and $\text{13}$ are formed, but also 3-mthylene-8-oxabicyclo [3.2.1]ovy-6-enes $\text{12}$ and $\text{14}$.     

Photo-oxygenations of 1H-azepine derivatives isolation and characterization of the [6+2] cycloaddition product

The reactions of 1H-azepine derivatives ($\text{1a-b}$ and $\text{4}$) with singlet oxygen gave the [6+2] cycloadducts ($\text{2a-b}$) and the [4+2] cycloadducts ($\text{3a-b}$ and $\text{5}$). The thermal and base-catalyzed rearrangements of the oxygen-adducts were investigated.     

Reduction of bicyclo[3.2.0] hept-2-en-6-one and 7,7-dimethylbicyclo[3.2.0]hept-2-en-6-one using dehydrogenase enzymes and the fungus mortierella ramanniana

Bicyclo[3.2.0]hept-2-en-6-one (1) was reduced with an alcohol dehydrogenase from $\text{Thermoanaerobium brockii}$ and a whole cell system ($\text{M. ramanniana}$) with excellent substrate enantioselectivity: 7,7-dimethylbicyclo[3.2.0]hept-2-en-6-one (2) was similarly reduced using the 3α,20β-hydroxysteroid dehydrogenase from Streptomyces $\text{hydrogenans}$ while $\text{M. ramanniana}$ furnished both 6S-alcohols (4a), (6b) with high optical purity.     

Reaction of neorl with thallium(III) perchlorate

Reaction of nerol ($\text{1}$) with thallium(III) perchlorate gave 6-oxabicyclo[3.2.1]octane derivatives ($\text{2}$) and ($\text{3}$), and 6,9-dioxabicyclo[3.3.1]nonane derivatives ($\text{4a–d}$) as the cyclization products.     

Cycloadditions des arsoles a haute temperature

At room temperature 1-phenyl-2,5-dimethylarsole $\text{1}$ gives [4+2] cycloadditions with dienophiles whereas at 160 °C it yields arsenic atoms which react with tolane to give the 1,4-diarsabicyclo[2.2.2]octatriene $\text{8}$; 1,2,5-triphenylarsole $\text{2}$ is less reactive at room temperature but isomerizes at 160°C to give the 2$\text{H}$-arsole $\text{5}$ which reacts as a diene with tolane to yield the 1-arsanorbornadiene $\text{6}$, and as a dienophile through its AsC double bond with dimethylbutadiene to give the 1-arsabicyclo[4.3.0]nonadiene $\text{7}$.